A COMPARATIVE ASSESSMENT OF PHYTOREMEDIATION AND

SLOW SAND FILTRATION TECHNOLOGIES FOR THE SECONDARY

TREATMENT OF SEWAGE EFFLUENT AND PUBLIC VIEWS ON THE

USE OF TREATED EFFLUENT

BY

NAOMI ADRAKI

(10105318)

THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA,

LEGON IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR

THE AWARD OF MPHIL ENVIRONMENTAL SCIENCE DEGREE

JULY, 2014

i

DECLARATION

I, Naomi Adraki, hereby declare that except for references cited, which I have duly

acknowledged, this work is the result of my own research undertaken under supervision

of Dr. Ted Annang and Dr. Dzidzor Yirenya-Tawiah of the Institute of Environment and

Sanitation Studies (IESS) towards the award of a Master of Philosophy Degree in

Environmental Science and that this work has neither in whole or in part, been presented

anywhere for the award of any other degree.

……………………………………… …………………………….

NAOMI ADRAKI DATE

(Student)

……………………………………… …………………………….

DR. TED ANNANG DATE

(Principal supervisor)

………………………………………… …………………………….

DR. DZIDZOR YIRENYA-TAWIAH DATE

(Co-supervisor)

ii

DEDICATION

This work is dedicated to my parents, Mr. and Mrs. Gabriel Anyigbah.

iii

ACKNOWLEDGEMENTS

I am very grateful to the almighty God for the gift of life and for the wisdom to carry out

this research. Many thanks to my supervisors, Dr. Ted Annang and Dr. Dzidzor Yirenya-

Tawiah for their direction and support. I also wish to thank Dr. Aidan of Biogas

Technologies Ltd for his great help.

To the Environmental Unit of Valley View University, especially Mr. Solomon Adei, I

say a very big thank you for granting me permission to use your Biogas facility for this

research.

Staff and students of IESS, thank you so much.

To my family and friends, I say thank you for your support and prayers. God bless you.

iv

ABSTRACT

This study evaluated and compared the performance efficiency of both technologies for

treating sewage effluent from a Biogas facility at Valley View University (VVU) and

also assessed public perception about the use of the treated effluent. Samples of the

sewage effluent from the VVU Biogas facility were subjected to slow sand filtration over

a ten week period using river bed sand and gravels, and phytoremediation using two

plants, Pistia stratiotes L and Ipomoea aquatica Forsk. Pistia stratiotes survived in the

raw effluent for five days, while Ipomoea aquatica survived longer (four weeks). The

findings revealed that both plants reduce contaminant levels. However, Ipomoea aquatica

had higher removal efficiency for phosphates (16.07%) and nitrates (100%). Pistia

stratiotes on the other hand was more efficient at improving electrical conductivity

(55.45%). The study showed that both slow sand filtration and phytoremediation using

Ipomoea aquatica are equally efficient at improving turbidity and Chemical Oxygen

Demand (COD). There were significant differences in values obtained for dissolved

oxygen (DO), nitrates and phosphates. Based on the differences, SSF performed better at

removing nitrates and phosphates while Ipomoea aquatica did better at enhancing

dissolved oxygen. No significant differences were recorded for electrical conductivity

(EC), Total Dissolved Solids (TDS), Total Suspended Solids (TSS), colour, and

Biochemical Oxygen Demand (BOD). However, when the means were compared, SSF

was better at removing TSS, BOD and colour whilst Ipomoea aquatica was better at

removing EC and TDS. Both technologies were successful at reducing microbial load.

This study also revealed that the parameters analyzed on the effluent discharged from the

VVU Biogas facility fell within acceptable guidelines with the exception of EC. Majority

v

of respondents agree that water is a scarce resource and that the Millennium

Development Goal (MDG) on water cannot be achieved. Majority of people interviewed

support the use of wastewater for medium contact options such as fire-fighting (71.6%),

industry (52.9%), construction of buildings (71.6%), toilet flushing (81.4%), commercial

car wash (46.1%), public parks and sports field irrigation (54.9%). Support for high

contact options such as swimming pool, aquifer augmentation and laundry was low;

10.7%, 29.4% and 34.3% respectively and this is because respondents consider the

treated water to be detrimental to health. Respondents supported the idea of wastewater

reuse for reasons of water conservation and minimization of dependency on treated water

whilst environmental protection ranked as the least frequent response. Education is

needed to sensitize the public on treatment and use of wastewater.

vi

LIST OF ABBREVIATIONS

AAS Atomic absorption spectrophotometry

ANOVA Analysis of variance

BOD Biochemical oxygen demand

COD Chemical oxygen demand

DO Dissolved oxygen

EC Electrical conductivity

FC Faecal coliforms

GEPA Ghana Environmental Protection Agency

SSF Slow sand filtration

TC Total coliforms

TDS Total dissolved solids

TSS Total suspended solids

VVU Valley View University

vii

TABLE OF CONTENTS

Content Page

DECLARATION ................................................................................................................. i

DEDICATION .................................................................................................................... ii

ACKNOWLEDGEMENTS ............................................................................................... iii

ABSTRACT ....................................................................................................................... iv

LIST OF ABBREVIATIONS ............................................................................................ vi

TABLE OF CONTENTS .................................................................................................. vii

LIST OF PLATES .............................................................................................................. x

LIST OF FIGURES ........................................................................................................... xi

LIST OF TABLES ........................................................................................................... xiv

CHAPTER ONE ................................................................................................................. 1

1.0 INTRODUCTION AND LITERATURE REVIEW .................................................... 1

CHAPTER TWO .............................................................................................................. 21

MATERIALS AND METHODS ...................................................................................... 21

2.1 Study site ................................................................................................................. 21

2.2 Materials .................................................................................................................. 22

2.3 Sewage treatment at VVU ....................................................................................... 23

2.4 Selection of sampling sites ...................................................................................... 23

2.5 Sampling of aquatic macrophytes ........................................................................... 23

viii

2.6 Preparation of filter media units ............................................................................. 25

2.7 Treatment of sample containers .............................................................................. 26

2.8 Monitoring of effluent quality at sampling site ....................................................... 26

2.8 Sampling of effluent for characterization................................................................ 27

2.9 Sewage effluent collection and experimental procedure ......................................... 28

2.9.1 Sewage effluent collection ................................................................................ 28

2.9.2 Slow Sand filtration (SSF) ................................................................................ 29

2.10 Phytoremediation ............................................................................................... 31

2.11 Laboratory analyses............................................................................................... 34

2.11.1 Physico-chemical analyses of raw and treated effluents ................................ 34

2.11.10 Analyses of Bacteriological Parameters of raw and treated effluents .......... 39

2.12 Social survey ......................................................................................................... 41

CHAPTER THREE .......................................................................................................... 42

3.0 RESULTS................................................................................................................ 42

3.1 Quality of sewage effluent from VVU biogas facility ............................................ 42

3.2 Phytoremediation using Pistia stratiotes and Ipomoea aquatica ............................ 43

3.3 Nitrogen and phosphorus uptake by plants ............................................................. 46

3.4 Contaminant removal efficiency of Ipomoea aquatica and Pistia stratiotes .......... 47

3.5 Weekly variations in water quality parameters after treatment with Ipomoea

aquatica ......................................................................................................................... 49

ix

3.6 Performance of Slow Sand Filtration ...................................................................... 53

3.7 Comparison of phytoremediation using Ipomoea aquatica and slow sand filtration

(SSF) technologies ........................................................................................................ 59

3.8 Microbial load ......................................................................................................... 80

3.9 Comparison of efficiency of experimental sand filter to the filtration system of the

Biogas plant ................................................................................................................... 82

3.10 Quality assessment of safety of treated effluent for disposal/reuse ...................... 83

3.11 Public perceptions on water scarcity and the reuse of wastewater ....................... 87

3.11.1 Demographic background of respondents .......................................................... 87

3.11.2 Environmental perceptions ................................................................................. 87

CHAPTER FOUR ........................................................................................................... 102

4.0 DISCUSSION ....................................................................................................... 102

CHAPTER FIVE ............................................................................................................ 119

5.0 CONCLUSIONS ................................................................................................... 119

REFERENCES ............................................................................................................... 122

APPENDICES ................................................................................................................ 133

x

LIST OF PLATES

Plate 1: Kpong Head Pond showing aquatic plants .......................................................... 22

Plate 2: Biogas facility of Valley View University .......................................................... 24

Plate 3: Filter media units; (a) gravels (5-10mm diameter), (b) coarse sand (2-3mm

diameter), (c) fine sand (0.4mm diameter) .......................................................... 25

Plate 4: Sampling effluent from intermediary chamber for characterization ................... 28

Plate 5: Slow Sand Filtration experimental set up at the greenhouse .............................. 29

Plate 6: Pistia stratiotes in different dilutions of effluent ................................................. 33

Plate 7: Ipomoea aquatica planted in sewage effluent ..................................................... 33

Plate 8: Condition of Pistia stratiotes days after planting in sewage effluent ................. 43

Plate 9: Condition of Ipomoea aquatica days after planting in sewage effluent .............. 43

Plate 10: Sewage effluent before (A) and after treatment (B) with Pistia stratiotes ........ 44

Plate 11: Sewage effluent before (a) and after treatment (b) with Ipomoea aquatica ...... 45

Plate 12: Sewage effluent before (A) and after seventh week (B) of slow sand filtration 58

xi

LIST OF FIGURES

Fig 1: Location map of study area .................................................................................... 21

Fig 2: Cross-section of slow sand filter media for Slow Sand Filtration of effluent ........ 30

Fig 3: Phosphate removal efficiency of Ipomoea aquatica and Pistia stratiotes ............. 47

Fig 4: Nitrate removal efficiency of Ipomoea aquatica and Pistia stratiotes ................... 47

Fig 5: COD removal efficiency of Ipomoea aquatica and Pistia stratiotes ..................... 48

Fig 6: EC removal efficiency of Ipomoea aquatica and Pistia stratiotes......................... 48

Fig 7: Concentration of dissolved oxygen (DO) in effluent after every week of treatment

with Ipomoea aquatica ........................................................................................ 49

Fig 8: Biochemical Oxygen Demand (BOD) of effluent after every week of treatment

with Ipomoea aquatica ........................................................................................ 50

Fig 9: Chemical Oxygen Demand (COD) of effluent after every week of treatment with

Ipomoeaaquatica ................................................................................................. 50

Fig 10: Electrical conductivity (EC) of effluent after every week of treatment with

Ipomoea aquatica ................................................................................................ 51

Fig 11: Total Dissolved Solids (TDS) of effluent after every week of treatment with

Ipomoea aquatica ............................................................................................... 51

Fig 12: Concentration of phosphates in effluent after every week of treatment with

Ipomoea aquatica ................................................................................................ 52

Fig 13: Concentration of nitrates in effluent after every week of treatment with Ipomoea

aquatica ............................................................................................................... 52

Fig 14: Rate of filtration through experimental sand filter ............................................... 53

Fig 15: Weekly variations in turbidity of effluent treated using SSF method .................. 54

Fig 16: Weekly variations in electrical conductivity (EC) of effluent treated using SSF 54

xii

Fig 17: Weekly variations in concentration of total dissolved solids (TDS) in effluent

treated using SSF ................................................................................................. 55

Fig 18: Weekly variations in concentration of Total Suspended Solids (TSS) in effluent

treated using SSF ................................................................................................. 55

Fig 19: Weekly variations in concentration of nitrates in effluent treated using SSF ...... 56

Fig 20: Weekly variations in concentration of phosphates in effluent treated using SSF 56

Fig 21: Weekly variations in concentration of dissolved oxygen in effluent treated using

SSF ...................................................................................................................... 57

Fig 22: Weekly variations in Biochemical Oxygen Demand (BOD) of effluent treated

using SSF ............................................................................................................. 57

Fig 23: Weekly variations in Chemical Oxygen Demand (COD) of effluent treated using

SSF ...................................................................................................................... 58

Fig 24: Source of water for domestic use by respondents ................................................ 88

Fig 25: Proportion of respondents who consider water to be a scarce resource ............... 89

Fig 26: Causes of water scarcity stated by respondents .................................................... 89

Fig 27: Sources of wastewater stated by respondents ....................................................... 90

Fig 28: How wastewater is generated by respondents ...................................................... 90

Fig 29: Uses of wastewater generated at home ................................................................. 91

Fig 30: Type of toilet facilty respondents have access to ................................................. 92

Fig 31: Methods of disposal of sewage as stated by respondents ..................................... 93

Fig 32: Respondents reasons for supporting wastewater reuse ........................................ 94

Fig 33: Types of health risks associated with wastewater reuse as stated by respondents 95

Fig 34: Respondents response on how health risks can be minimized ............................. 96

xiii

Fig 35: Response of respondents to the use of treated wastewater for irrigation of food

crops .................................................................................................................... 97

Fig 36: Response of respondents to the use of treated wastewater for fire fighting ......... 98

Fig 37: Response of respondents to the use of treated wastewater for industry ............... 98

Fig 38: Response of respondents to the use of treated wastewater for construction of

buildings .............................................................................................................. 99

Fig 39: Response of respondents to the use of treated wastewater for swimming pool ... 99

Fig 40: Response of respondents to the use of trated wastewater for aquifer augmentation

........................................................................................................................... 100

xiv

LIST OF TABLES

Table 1: Quality of sewage effluent from intermediary chamber (A) and final outlet (B)

of the Valley View University (VVU) Biogas facility. .................................... 42

Table 2: Phosphorus and nitrogen accumulation in Ipomoea aquatica and Pistia stratiotes

at the end of experiment ................................................................................... 46

Table 3: Comparison of p H of effluent treated using SSF with effluent from treatment

with Ipomoea aquatica ..................................................................................... 60

Table 4: Comparison of the concentration of dissolved oxygen (DO) of effluent treated

using SSF with effluent treated with Ipomoea aquatica ................................. 61

Table 5: Comparison of turbidity of effluent treated using SSF with effluent from

treatment with Ipomoea aquatica ..................................................................... 63

Table 6: Comparison of EC of effluent treated with SSF with effluent from treatment

with Ipomoea aquatica ..................................................................................... 65

Table 7: Comparison of concentration Total Dissolved Solids (TDS) of effluent treated

using SSF with effluent from treatment with Ipomoea aquatica ..................... 67

Table 8: Comparison of concentration of Total Suspended solids (TSS) of effluent treated

using SSF with effluent from treatment with Ipomoea aquatica ..................... 69

Table 9: Comparison of colour of effluent treated using SSF with effluent from treatment

with Ipomoea aquatica ..................................................................................... 71

Table 10: Comparison of concentration of nitrates in effluent treated using SSF with

effluent treated using Ipomoea aquatica .......................................................... 73

Table 11: Comparison of phosphate concentration in effluent treated using SSF with

effluent from treatment with Ipomoea aquatica ............................................... 75

Table 12: Comparison of Biochemical Oxygen Demand (BOD) of effluent treated with

SSF with effluent from treatment with Ipomoea aquatica ............................... 77

xv

Table 13: Comparison of Chemical Oxygen Demand (COD) of effluent treated using SSF

with effluent from treatment with Ipomoea aquatica ...................................... 79

Table 14: Microbiological characteristics of sewage effluent before and after treatment 80

Table 15: Comparison of the quality of effluent for ten weeks of SSF to quality of

effluent passing through the filtration system of the VVU Biogas plant ......... 82

Table 16: Assessment of safety of effluent treated using SSF for disposal/reuse ............ 83

Table 17: Assessment of the quality of effluent treated using Pistia stratiotes for

disposal/use ...................................................................................................... 84

Table 18: Assessment of the quality of effluent treated using Ipomoea aquatica for

disposal/ use ..................................................................................................... 86

Table 19: Demographic characteristics of respondents .................................................... 87

1

CHAPTER ONE

1.0 INTRODUCTION AND LITERATURE REVIEW

All around the world, the demand for water resources is accelerating with increasing

population growth. Most water bodies are under threat due to pollution. It is becoming

increasingly important to seek alternative sources of water to meet the demand of the ever

increasing global population. Increasing demands on water resources for domestic,

commercial, industrial and agricultural purposes have made wastewater reclamation an

attractive option for conserving and extending available water supplies. Thus, wastewater

reclamation and reuse have become essential components of water resource management

plans throughout the world.

One of the major water resource management concerns throughout the world is the safe

disposal of sewage. In many countries especially the developing ones, disposal of raw

untreated sewage into natural waters is a common practice. This poses a great hazard for

the environment and a health risk for both human and animal life.

In recent years, sewage treatment strategies have been shifted to one of the most

promising methods i.e. biological anaerobic treatment. This method is capable of treating

sewage to produce renewable energy (biogas), leaving behind an effluent which is

usually discarded. This effluent is a substantial water resource that has to be sustainably

managed, rather than discarded.

Sewage effluent is composed of compounds of agricultural value including organic

matter, nitrogen, phosphorus and a lesser amount of calcium, sulphur and magnesium. It

may also contain pollutants such as heavy metals, organic pollutants and pathogens

2

which may have significant adverse effects on human health and the environment, thus

limiting its use. However, further treatment of the effluent can produce a high quality

effluent for use.

Treatment technologies for wastewater need to be appropriate and sustainable. They

should also be efficient but less costly and easy to operate and maintain. In developing

countries with warm climates such as Ghana, natural systems are considered more

suitable.

Slow Sand filtration (SSF) and phytoremediation are natural treatment systems that can

be used for treatment of wastewater. These technologies have proven to reduce

contaminant levels to tolerable levels. Materials needed for the use of these technologies

are readily available.

Global water crises

Fresh water is a scarce and unevenly distributed resource, not matching patterns of

human development (Corcoran et. al., 2010). According to UNDESA (2009), nearly 900

million people worldwide still do not have access to safe water. The population of the

world is increasing rapidly and is expected to grow by almost a third to over 9 billion

people in the next 40 years (UNFPA, 2009), resulting in increased water usage. The

African continent has the lowest total water supply coverage of any region in the world,

with only 64% of the population having access to improved water supply (WHO, 2000).

One other contributory factor to the water scarcity problem is water pollution. The

available water resources which should cater for the needs of the ever growing global

3

population are constantly being polluted the chief sources of water pollution being

sewage, industrial wastes, fossils, fuel and nuclear power plants (Egun, 2010).

Currently, there is increasing awareness of the impact of sewage contamination on water

bodies. According to the World Bank, the greatest challenge in the water and sanitation

sector over the next two decades will be the implementation of low cost sewage treatment

that will at the same time permit selective reuse of treated effluents for agricultural and

industrial purposes (Jhansi and Mishra, 2012)

Sewage treatment

Wastewater (sewage) treatment is an expensive process, both in terms of land required

and the energy consumed (Mekala et. al., 2008). More than 65% of sewage is treated in

developed countries (WHO and UNICEF, 2000) for various reasons, but only after

suitable treatment and guidelines are in place for recycling. In Africa, almost no sewerage

is treated (WHO and UNICEF, 2000).

Generally there is lack of sustainable options for treating sewage in many cities in

developing countries. Most cities in developing countries have an aging, inadequate or

even non-existent sewage infrastructure, unable to keep up with rising population. The

United Nations Development Programme (UNDP) reports that in 2000 only 2 % of the

cities in sub-Saharan Africa had sewage treatment and only 30 % of these were operating

satisfactorily.

The cities of Ghana are no exception to the poor sewage treatment coverage. It has been

shown that out of the 44 wastewater treatment plants in Ghana, only 20 % are working,

most of them below design standard (IMWI, 2012). Consequently, sewage sludge from

4

on-site sanitation systems (OSS) is collected and disposed-off in the raw and untreated

form indiscriminately into drainage ditches, inland waters and coastal waters. Discharge

of untreated effluent into water bodies puts at risk riparian communities which depend on

these waters for domestic and personal use (Tchobanologous et al., 2003). Biodiversity is

also affected as a result of water pollution. In many developing countries, contamination

of faecal origin appears to be responsible for many enteric diseases notably in children.

Africa has the worst statistics for cholera and child diarrhoea (Warner, 2000).WHO

reported in 2000 that in Africa, 155 children die every hour of everyday from sanitation,

hygiene and water related diseases. The number of cholera cases reported from Africa is

increasing every year. A total of 187,545 cholera cases and 8,051 deaths were officially

reported in the African Region (WHO, 2000). Recently, several cholera outbreaks were

reported in different African countries: Zimbabwe, Tanzania, Rwanda, Kenya, Angola,

Republic of Congo and Ghana due to contaminated drinking water (Bahri et al., 2012)

Most of the current sewage treatment technologies in developing countries lack

sustainability (Jhansi and Mishra, 2012). The conventional centralized system uses large

volumes of water to dilute human excreta and thereafter transports them out of the

settlement which makes this system unsustainable because apart from the fact that large

volumes of water are lost, most of the sewage is transported and deposited in water

bodies leading to contamination of the water causing public health hazards. There is also

a loss of nutrient resources of agricultural value such as nitrogen and phosphorus.

5

Another reason for the unsustainable treatment systems in developing countries is that

they are simply copied from western treatment systems without considering the

appropriateness of the technology for the culture, land and climate. Thus, many of the

implemented installations are abandoned due to high cost of running the system and

repairs (Jhansi and Mishra, 2012).

In order to achieve effective sewage treatment in developing countries, there is the need

to apply appropriate treatment technologies which are effective, simple to operate and

low cost in terms of investment, operation and maintenance.

One of the effective treatment options for developing countries is anaerobic digestion

(Jhansi and Mishra, 2012). This technology has been proven to have high treatment

efficiency and its operation requires no or very low energy.

Anaerobic digestion consists of several interdependent, complex sequential and parallel

biological reactions in the absence of oxygen in which the products from one group of

microorganisms serve as substrates for the next resulting in transformation of organic

matter (Parawira, 2004). The products resulting from the transformation are biogas and

nutrient rich effluent called digestate.

In this system, anaerobic bacteria degrade organic materials in the absence of oxygen and

produce methane and carbon dioxide. The methane can be reused as an alternative energy

source or biogas. Other benefits include a reduction of total bio-solids volume of up to

50-80% and a final effluent that is biologically stable and can serve as rich humus for

agriculture (Jhansi and Mishra, 2012). This anaerobic treatment technology can be

6

applied on a very small or a very large scale making it a sustainable option for a growing

community.

However, effluents from anaerobic reactors treating domestic sewage can rarely comply

with the emission standards. Besides the remaining fraction of particulate and soluble

organic matter, the main important constituents or components deserving attention are

nutrients and pathogens. These are not removed efficiently in the most commonly used

anaerobic reactors (Foresti, 2002).

Wastewater reuse

Current waste management practices propose that sanitation systems whenever feasible

should allow for recycling of organic matter and nutrients in human excreta (Esrey et al.,

1998). As a result, treatment strategies and technological options for sewage sludge and

solid waste have to be developed to allow the optimum recycling of nutrients and organic

matter.

One of the important and sustainable ways to reduce the impact of water scarcity and

pollution is wastewater recycling and reuse. Wastewater effluent is the most readily

available and cheapest source of additional water and provides a partial solution to the

water scarcity problem (Al-Dadah, 2013).

In recent years, the reuse of treated effluent that hitherto was discharged into the

environment from municipal wastewater treatment plants is receiving an increasing

attention as a reliable water resource. In many countries, wastewater treatment for reuse

is an important dimension of water resources planning and implementation. This is aimed

7

at releasing high quality water supplies for potable use. Some countries, such as Jordan

and Saudi Arabia, have national policies aimed at reusing all treated wastewater effluents,

thus have made considerable progress towards this end (Akpor and Muchie, 2011). In

China, sewage use in agriculture developed rapidly several decades ago and millions of

hectares are irrigated with sewage effluent (Akpor and Muchie, 2011). The general

acceptance is that wastewater use in agriculture is justified on agronomic and economic

grounds, although care must be taken to minimize adverse health and environmental

impacts (Sowers, 2009). Furthermore, wastewater reuse is increasingly becoming

important for supplementing drinking water needs in some countries around the world.

The option of reuse of wastewater is becoming necessary and possible as a result of

increased climate change, which leads to droughts and water scarcity, and the fact that

wastewater effluent discharge regulations have become stricter leading to a better water

quality (Rietveld et al., 2009).

Wastewater can be an essential resource for supporting livelihoods with proper

management. The treatment and reuse of wastewater in agriculture can provide benefits

to farmers in conserving freshwater resources, improving the integrity of the soil and

preventing discharge to surface and ground waters. In the State of California and in

Mexico, reclaimed water is used for irrigation (Corcoran et. al., 2010).

The use of raw untreated wastewater for irrigation is a common practice in Africa.

Practices range from the use of polluted surface water/raw wastewater to the piped

distribution of secondary or tertiary treated wastewater to irrigate different kinds of crops

and trees (IWMI, 2006). Due to poor transportation systems, 70-90% of the most

perishable vegetables consumed in many African cities such as Dakar, Bamako,

8

Ouagadougou, Accra, Addis Ababa and Nairobi are also grown within the city boundary,

using highly polluted water sources, mostly of domestic origin (Drechsel et al., 2006).

There are only a few countries in Africa namely South Africa, Tunisia and Namibia with

experience in planned reuse and a record of wastewater treatment plants producing a safe

effluent for irrigation. In most of the other countries, including Ghana partially treated or

untreated urban wastewater is widely used to irrigate vegetables, rice and fodder for

livestock. Wastewater irrigation, though a major economic contributor in terms of jobs

and food supply can also be a major health risk for farmers and consumers Among the

health risks of particular concern are endemic and epidemic diseases such as cholera and

typhoid (WHO, 2006).

Wastewater irrigation also raises issues related to environmental protection as its nutrient,

salt and contaminant levels can be high. However, farmers do not have a choice to use

“wastewater” or not, as it is often difficult to find clean water sources in and around most

cities. Wastewater has many advantages for farmers as it contains significant amounts of

nutrients for food crop production that reduce the need for chemical fertilizers. Organic

matter, nitrogen, phosphorus, and potassium in wastewater may improve soil fertility,

enhance plant development and increase agricultural productivity. More importantly,

however, it is a reliable water supply, usually ‘free-of-charge’, and readily available.

Wastewater reuse supports the livelihood of many farmers and traders and plays a

significant role in poverty alleviation. It also provides a niche for urban food supply

complementing rural production (Drechsel et al., 2007).

9

Other wastewater reuse options are landscape irrigation, industrial recycling and reuse,

recreational/environmental uses, groundwater recharge, habitat wetlands, non-potable

miscellaneous uses and augmentation of potable supplies (Hagare and Dharmappa, 1999).

The reuse of wastewater for the above mentioned purposes can help to conserve water.

Characteristics of wastewater

Physico-chemical characteristics

The composition of wastewater varies widely depending on the type of activity producing

the wastewater.

The physico-chemical characteristics of wastewater that are of special concern are pH,

dissolved oxygen (DO), oxygen demand (chemical and biological), solids (suspended and

dissolved), nitrogen (nitrite, nitrate and ammonia), phosphate, and metals (Larsdotter,

2006).

The hydrogen-ion concentration is an important quality parameter of both natural and

waste waters. It is used to describe the acid or base properties of wastewater. A pH less

than 7 in wastewater effluent is an indication of septic conditions while values less than 5

and greater than 10 indicate the presence of industrial wastes. An indication of extreme

pH is known to damage biological processes in biological treatment units (Gray, 2002).

Another parameter that has significant effect on the characteristics of water is dissolved

oxygen. It is required for the respiration of aerobic microorganisms. The actual quantity

of oxygen that can be present in solution is determined by the solubility, temperature,

10

partial pressure of the atmosphere and the concentration of impurities such as salinity and

suspended solids in the water (Metcalf and Eddy, 2003).

Oxygen demand, which may be in the form of Biochemical Oxygen Demand (BOD) or

Chemical Oxygen Demand (COD), is the amount of oxygen used by microorganisms as

they feed upon the organic solids in wastewater (FAO, 2007). The five day BOD (BOD5)

is the most widely used organic pollution parameter applied to wastewater. The presence

of sufficient oxygen promotes the aerobic biological decomposition of an organic waste

(Metcalf and Eddy, 2003). Although BOD test is widely used, it has a number of

limitations, which include the requirement of a high concentration of active acclimated

microorganisms and the need for treatment when dealing with toxic wastes, thus reducing

the effects of nitrifying organisms. The BOD measures only the biodegradable organics

and requires a relatively long time to obtain test results (Gray, 2002; Metcalf and Eddy,

2003) but the COD test measures the oxygen equivalent of the organic material in

wastewater that can be oxidized chemically. The ratio of COD to BOD provides a useful

guide to the proportion of organic material present in wastewaters, although some

polysaccharides, such as cellulose, can only be degraded anaerobically and so will not be

included in the BOD estimation (Metcalf and Eddy, 2003).

The amount of solids in drinking water systems has significant effects on the total solids

concentration in the raw sewage. In spite of this wastewater is normally 99.9 % water, 0.1

% of it is comprised of solids. Although there are different ways of classifying solids in

wastewater, the most common types are total dissolved solids (TDS), total suspended

solids (TSS), settleable, floatable and colloidal solids, and organic and inorganic solids.

11

Heavy metals are one of the most persistent pollutants in wastewater. Heavy and trace

metals are also of importance in water. The metals of importance in wastewater treatment

are As, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Hg, Mo, Ni, K, Se, Na, V and Zn. Living

organisms require varying amounts of some of these metals (Ca, Co, Cr, Cu, Fe, K, Mg,

Mn, Na, Ni and Zn) as nutrients (macro or micro) for proper growth. Other metals (Ag,

Al, Cd, Au, Pb and Hg) have no biological role and hence are non-essential (Hussein et

al., 2005). Heavy metals in wastewater is due to discharges from residential dwellings,

groundwater infiltration, and industrial discharges. The accumulation of these metals in

wastewater depends on many local factors, such as the type of industries in the region,

way of life and awareness of the impact on the environment through the careless disposal

of wastes (Hussein et al., 2005; Silvia et al., 2006). The danger of heavy and trace metal

pollutants in water lies in two aspects of their impact. Firstly, heavy metals have the

ability to persist in natural ecosystems for an extended period, and, secondly, they have

the ability to accumulate in successive levels of the biological food chain. Although

heavy metals are naturally present in small quantities in all aquatic environments, it is

almost exclusively through human activities that these levels are increased to toxic levels

(Nelson and Campbell, 1991). The methods for determining the concentrations of these

metals vary in complexity according to the interfering substances that may be present.

Typical methods of determining their concentrations include flame atomic absorption,

atomic absorption spectrophotometry (AAS), inductively coupled plasma (ICP), and

inductively coupled plasma (ICP)/ mass spectrometry (APHA, 2001).

Surface waters contain levels of phosphorus in various compounds, which are essential

constituents of living organisms. In natural conditions, the phosphorus concentration in

12

waters is balanced. However, when phosphorus input to waters is higher than that which

a population of living organisms can assimilate, the problem of excess phosphorus

content occurs (Rybicki, 1997). An excess content of phosphorus in receiving waters

usually leads to extensive algal growth (eutrophication). Controlling phosphorus

discharge from municipal and industrial wastewater treatment plants is a key factor in

preventing eutrophication of surface waters (Department of Natural Science, 2006). The

following groups of phosphorus compounds are of great importance in wastewater:

organic phosphates, condensed phosphates and inorganic phosphates. Although

phosphate itself does not have notable adverse health effects, phosphate levels greater

than 10 mg/L may interfere with coagulation in water treatment plants (McCasland et al.,

2008).

Nitrogen is important in wastewater management. It can have adverse effects on the

environment, since its discharge above the required limit of 10 mg/L can be undesirable

due to its ecological and health impacts (Kurosu, 2001; Amir et al., 2004). Nitrogen is

required by all organisms for the basic processes of life to make proteins, grow and

reproduce. It is recycled continually by plants and animals. Most organisms cannot use

nitrogen in the gaseous form (N) for their nutrition, so they are dependent on other

organisms to convert it into other forms (Jenkins et al., 2003). Ammonia, nitrate and

nitrite make up the inorganic forms of nitrogen (Hurse and Connor, 1999). Organic and

inorganic forms of nitrogen may cause eutrophication problems in nitrogen-limited

freshwater lakes and in estuarine and coastal waters. In the environment, ammonia is

oxidized to nitrate, creating an oxygen demand and low dissolved oxygen in surface

waters (Kurosu, 2001). Despite the fact that nitrate levels that affect infants do not pose a

13

direct threat to older children and adults, they indicate the presence of other serious

residential or agricultural contaminants, such as bacteria and pesticides (McCasland et

al., 2008). Methemoglobinemia is the most significant health problem associated with

nitrate in water. Usually, blood contains an iron-based compound (hemoglobin) that

carries oxygen, but when nitrite is present, hemoglobin can be converted to

methemoglobin, which cannot carry oxygen. Similarly, nitrogen in the form of ammonia

is toxic to fish and exerts an oxygen demand on receiving water by nitrifiers (CDC,

2002).

Microbiological characteristics

The major microorganisms found in wastewater are viruses, bacteria, fungi, protozoa and

helminthes. Although various microorganisms in water are considered to be critical

factors in contributing to numerous waterborne outbreaks, they play many beneficial

roles in wastewater influents (Kris, 2007). Traditionally, microorganisms are used in the

secondary treatment of wastewater to remove dissolved organic matter (Akpor and

Muchie, 2011). Apart from solid matter reduction, wastewater microbes are also

involved in nutrient recycling, such as phosphate, nitrogen and heavy metals. If nutrients

that are trapped in dead materials are not broken down by microbes, they will never

become available to help sustain the life of other organisms in the breakdown process.

Microorganisms are also responsible for the detoxification of acid mine drainage and

other toxins in wastewater (Ward-Paige et al., 2005). Microbial pollutants can also serve

as indicators of water quality.

The detection, isolation and identification of the different types of microbial pollutants in

wastewater are always difficult, expensive and time consuming. To avoid this, indicator

14

organisms are always used to determine the relative risk of the possible presence of a

particular pathogen in wastewater (Paillard et al., 2005). For instance, enteric bacteria,

such as coliforms, Escherichia coli, and faecal streptococci are used as indicators of

faecal contamination in water sources (Momba and Mfenyana, 2005).

Wastewater treatment

Wastewater treatment is an expensive process thus many of the underdeveloped and

developing nations of Africa and Asia have not been able to treat their wastewater to

appropriate levels and continue to use it in agriculture with deleterious long-term effects

on soil, groundwater and human health. However, many of the water scarce cities in

Europe, North America and Australia are able to treat their wastewater to appropriate

levels and recycle it in industries, residential areas, urban gardens and sports lawns.

While the lack of wastewater treatment to appropriate levels before use is a major

problem in developing countries, the high cost of wastewater recycling is the major

problem in developed countries (Mekala et. al., 2008)

The growing concern over the impact of sewage contamination on water bodies and the

increasing scarcity of water in the world along with rapid population increase in urban

areas give reasons to consider appropriate technologies for the post treatment of

anaerobic effluent in order to achieve the desired effluent quality and save receiving

water bodies.

Slow sand filtration (SSF)

The use of slow sand filtration (SSF) to improve the quality of water dates back to

hundreds of years (Bourdon et. al., 2012) and is a sustainable approach to purifying

15

water. It is a desirable technology in developing countries where water purification

capabilities are poor and in developed countries with technically advanced water

treatment plants. The use of SSF requires minimal use of chemicals, low electricity

requirements and marginal operation and startup costs.

Slow Sand Filtration operates by allowing untreated water to slowly percolate through a

bed of porous sand, with the influent water source introduced over the top surface of the

filter area, and effluent collected and drained from the bottom. The ability of SSF

method to purify water is the result of several mechanisms that occur during filtration. It

requires a continuous filtration of raw water through the sand bed. As the raw water

filters through the sand grains, particles in the raw water are removed by transport and

attachment processes such as adsorption and ion exchange. The most basic transport

mechanism that occurs in SSF is the straining of particles out of the water by the sand

grains. Straining occurs when the particles in the water larger than the voids in the sand

grains become trapped and lodged in the sand bed. As more and more particles become

lodged in the sand bed, the pore size between the sand gains and the particles decrease,

allowing for a larger percentage of particles in the water to be removed. The majority of

this screening process occurs at the surface of the filter. Sedimentation of the particles

onto the sand grains is another transport mechanism. The settling action occurs as

gravity forces the particles to move downward onto the top surfaces of the sand grains.

Since the flow rate through SSF is gradual, the particles will remain settled on top of the

sand grains and removed from the effluent of the SSF system.

The sedimentation removal of the particles is enhanced by attachment processes. Once

the particle has made contact with the sand grains, Van der Waals forces can help

16

maintain that particle on the sand grain. Another and stronger attachment mechanism is

the adhesion of particles to the “schmutzdecke” layer or “dirt cover”. The

“schmutzdecke” layer consists of the organic matter that settles on the filter surface and

becomes the breeding ground for bacteria and microorganisms. As the “schmutzdecke”

layer develops it becomes a sticky, gelatinous film and adheres a great deal of the

particles from the raw water. The layer takes several weeks to form and can consist of

bacteria, fungi, protozoa, algae, and microscopic aquatic organisms, once fully

developed. The organic matter in the raw water is trapped by the “schmutzdecke” layer

and utilized by the bacteria and microorganisms as a food source, thus reducing the

organic matter into water, carbon dioxide, and inorganic salts. The “schmutzdecke” layer

provides the primary means for eliminating organic matter in the slow sand filtered

effluent.

The transport and attachment processes in an established SSF have the ability to greatly

improve the quality of the raw water. No other single process in typical drinking water

treatment plants has the ability to improve the physical, chemical, and bacteriological

quality of the raw water as an established Slow sand filter (Bourdon et. al, 2012).

Phytoremediation

Phytoremediation is defined as the efficient use of plants to remove, detoxify or

immobilize environmental contaminants in a growth matrix (soil, water or sediments)

through the natural, biological, chemical or physical activities and processes of plants

(Peuke and Rennenberg, 2005). Phytoremediation techniques require very low costs to

carry out (Jamil et. al., 2009). The method is widely recognized and accepted as an

17

ecologically responsible alternative to the environmentally destructive chemical

remediation methods (Ahmadpour et. al., 2010). Aquatic macrophytes can effectively

reduce total nitrogen, total phosphorus and chemical oxygen demand (Sooknah and

Wilkie 2004).

The principles of phytoremediation system are to clean up contaminated water which

includes the identification and implementation of efficient aquatic plant, uptake of

dissolved nutrients and metals by growing plants and the harvest and beneficial use of the

plant biomass produced from the remediation system (Lu, 2010). The most important

factor in implementing phytoremediation is the selection of an appropriate plant (Stefani

et.al, 2011) which should have high uptake of both organic and inorganic pollutants and

grow well in polluted water. The uptake and accumulation of pollutants vary from plant

to plant and from species to species within a genus (Singh et. al., 2003). The economic

success of phytoremediation largely depends on photosynthetic activity and growth rate

of plants (Xia and Ma, 2006) and low to moderate amount of pollution (Jamuna and

Noorjahan, 2009).

Numerous aquatic plants have demonstrated considerable potential for nutrient removal

from various types of wastewaters (Sooknah and Wilkie, 2004). Some of the aquatic

plants used in the treatment of wastewater include Water hyacinth (Eichhornia

crassipes), water lettuce (Pistia stratiotes), duckweed (Lemna sp.), Bulrush (Typha sp),

Vetiver grass (Chrysopogon zizanioides) and common reed (Phragmites australis)

(Piyush et. al., 2012). In this study, Ipomoea aquatica and Pistia stratiotes were used.

18

Water lettuce (Pistia stratiotes L)

Pistia stratiotes L is a floating perennial commonly called water lettuce belonging to the

family Araceae. It floats on the surface of water and its roots hang submerged beneath

floating leaves (Dipu et. al., 2011). The leaves can be up to 14 cm long and have no stem.

They are light green with parallel veins, wavy margins and are covered in short hairs

which form basket-like structures and help in trapping air bubbles, increasing the

buoyancy of the plants. The flowers are dioecious and are hidden in the middle of the

plant among the leaves. The plant can reproduce both sexually and vegetatively (Dipu et.

al., 2011).

Water lettuce has a minimum growth at temperature 15°C (Kasselmann, 1995). Fonkou

et.al., (2002) stated that the water lettuce doubles its biomass in just over five days,

triples it in ten days, quadruples it in twenty days and has its original biomass multiplied

by a factor of nine in less than one month. This indicates that the maximum period to

allow the plant in the system is twenty five days (Piyush et. al., 2012).

In the tropics, water lettuce is used in phytoremediation systems because compared to

native plants; it shows higher nutrient removal efficiency with increased nutrient uptake

capacity, fast growth rate and big biomass production (Reddy and Sutton, 1984).

Water spinach (Ipomoea aquatica Forsk)

Ipomoea aquatica is a semi-aquatic tropical plant grown as a leaf vegetable belonging to

the family Convolvulaceae. It is a very good source of nutrients (Visitacion et. al., 2011)

and acts as a good metal and toxin accumulator (Teerakun and Reungsang, 2005).

19

Public perception and acceptance of wastewater reuse

A successful implementation of a wastewater reuse project is dependent not only on its

economic and environmental feasibility but mainly on the support and acceptability of the

general public that ultimately patronize and might be affected by the reuse project. Reuse

schemes may face public opposition resulting from a combination of prejudiced beliefs,

fear, attitudes, lack of knowledge and general distrust often resulting from the frequent

failures of wastewater treatment facilities worldwide (Jeffrey and Temple, 1999).

Results from several surveys on public attitudes toward wastewater reuse options have

been published, the data collected mainly in the United States of America, Western

Europe and Australia. Results of these surveys indicate that, a large majority of the public

support water reuse as a concept and public support for reuse decreases as the degree of

contact with the reclaimed water increases. Crook (2003) reported that in the US the

public generally supports non-potable reuse while acceptance of potable reuse is

problematic, with typically less than 50% support. . Much less information is available

regarding the attitude toward the issue in other regions and under different environmental

and climatic conditions (Friedler et. al., 2006)

The primary concerns of the public are costs and public health protection, thus uses that

result in financial gains and involve minimal degree of contact with the reclaimed water

are favoured (Friedler et. al., 2006).

20

Objectives

The main objective of this study was to assess performance efficiency of slow sand

filtration and phytoremediation for effective secondary treatment of sewage effluent from

a biogas plant

The specific objectives were to:

1. characterize the sewage effluent after anaerobic digestion of sewage in the

Biogas facility of Valley View University (VVU)

2. conduct phytoremediation using two macrophyte species namely Pistia statiotes

and Ipomoea aquatica to identify the better macrophyte for the uptake of specific

pollutants

3. conduct slow sand filtration of the raw effluent using river bed sand

4. compare the experimental slow sand filter to the filtration system of the biogas

facility

5. evaluate and compare the performance of slow sand filtration and

phytoremediation technologies in treating sewage effluent

6. assess the safety of the treated effluent for disposal and/or reuse

7. assess public perception of wastewater reuse

21

CHAPTER TWO

MATERIALS AND METHODS

2.1 Study site

The study site was the Valley View University (VVU) located at Oyibi in the greater

Accra Region of Ghana.

Fig 1: Location map of study area

22

2.2 Materials

(i) Raw sewage effluent

The raw sewage effluent was obtained from the Biogas facility of the

Valley View University (VVU)

(ii) Sand and gravels for Slow Sand Filtration (SSF)

The river sand and gravels for the SSF experiment were obtained from the

Volta River at Asutuare

(iii) Aquatic macrophytes for phytoremediation were obtained from the Kpong

Head Pond

Plate 1: Kpong Head Pond showing aquatic plants

23

2.3 Sewage treatment at VVU

The method of sewage treatment at VVU is anaerobic digestion. In this system, there is a

digestor (Plate 2) where anaerobic bacteria degrade organic materials (in the absence of

oxygen) and produce methane and carbon dioxide. The methane is stored and used in the

school’s kitchen (for cooking). The effluent from the digestor is transported to an

intermediary chamber (Plate 2). From this chamber, the effluent passes into a filtration

system made of activated charcoal and then discharged into a mango plantation (Plate

3.1d)

2.4 Selection of sampling sites

The sewage effluent was obtained from the Biogas facility of the Valley View University.

Samples were taken from two points for analyses; the intermediary chamber and the final

outlet (Plate 2). Effluent samples for sand filtration and phytoremediation were collected

from the intermediary chamber (Plate 3.1)

2.5 Sampling of aquatic macrophytes

Two aquatic macrophytes namely Pistia stratiotes L and Ipomoea aquatica Forsk were

selected and identified. Pistia stratiotes is a floating species whilst Ipomoea aquatica is

an emergent species. Fresh and healthy macrophytes were collected from the Kpong

Head Pond and transported along with adequate quantity of water from the source (to

prevent wilting) to the greenhouse at the Botany Department of the University of Ghana,

Legon.

24

(a) Digestor

(b)

Filtration bed Intermediary chamber

(c) Final outlet

(d) Mango plantation

Plate 2: Biogas facility of Valley View University

25

2.6 Preparation of filter media units

Sand and gravels harvested from the Volta River at Asutuare were washed thoroughly

using ordinary tap water to remove sediments, sun dried and sieved to obtain desired

fractions. Below are the different fractions of sand and gravels used for the Slow Sand

Filtration (SSF).

Plate 3: Filter media units; (a) gravels (5-10mm diameter), (b) coarse sand (2-3mm

diameter), (c) fine sand (0.4mm diameter)

a

b

c

26

2.7 Treatment of sample containers

The following measures were adhered to in avoiding possible contamination of samples

during sampling. The sampling containers with well-fitted stoppers were pre-treated by

washing with acetone to get rid of organic substances such as grease and fat residues.

They were then washed with detergent and rinsed with de-ionised water and then soaked

in 0.1 M nitric acid solution for 48 hours. The containers were finally rinsed several times

with de-ionised water before used for taking and holding water samples. Water samples

that were not analyzed immediately at the site were transported on ice to the laboratory

where they were stored in a refrigerator below 4oC. Precautions were taken as to the

number of days the samples should be stored to avoid inaccuracy.

2.8 Monitoring of effluent quality at sampling site

Characterization of sewage effluent, both for the intermediary and final outlets was

carried out twice a month over a period of four months (February 2014-May 2014).

Reject water samples from the intermediary and final out-let points of the plant were

taken for physico-chemical analyses. Parameters including temperature, pH, conductivity,

colour, turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD),

total suspended solids (TSS), total dissolved solids (TDS), nitrate, phosphate and heavy

metals like Pb, Cd, Cu, Ni, Zn, Fe, Cr were determined. Microbiological parameters such

as total heterotrophic bacteria (THB), total coliform and faecal coliforms were also

determined.

27

2.8 Sampling of effluent for characterization

2.8.1 Sampling for physico-chemical tests and field measurements

Cleaned 500 ml plastic bottles were filled with effluent samples from the intermediary

chamber and the final outlet. This was subsequently used in the laboratory for off-site

analyses. pH, temperature, conductivity and dissolved oxygen of the effluents were

measured in-situ.

2.8.2 Biochemical Oxygen Demand (BOD) and Dissolved Oxygen (DO) Sampling

A plain bottle and one dark bottle (painted with bitumen to prevent possibility of

photosynthetic production of oxygen) were used for sampling. The plain one was used for

dissolved oxygen sampling and the dark bottles were used for BOD sampling. The bottles

were filled with the waste water to overflow in order to avoid any air bubbles from

getting trapped in the bottles. The dissolved oxygen samples were fixed on site with 2 ml

each of Winkler 1 (Manganous chloride) and Winkler 2 (alkaline-iodide-azide reagent).

Samples, which were not analyzed within 2 hours of collection, were kept at or below

4oC but brought to 20oC before analysis in the laboratory.

2.8.3 Trace Metals Sampling

Water samples for analysis of the trace metals Iron, Cadmium, Copper Nickel, Zinc, Lead

and Chromium, were collected in plastic vials and fixed on the field with nitric acid.

They were then kept at or below 4oC but brought to 20oC before analysis in the

laboratory.

28

2.8.4 Bacteriological sampling

Glass bottles of 500 ml capacity with metal caps were used to collect the effluents at the

intermediary and final outlets. The bottles were sterilized before use and the mouths

covered with aluminium foil to avoid contamination during sample collection. The

samples were stored on ice at 4ºC and transported to the laboratory for analyses.

Plate 4: Sampling effluent from intermediary chamber for characterization

2.9 Sewage effluent collection and experimental procedure

2.9.1 Sewage effluent collection

Sewage effluent for the experiment was collected from the intermediary chamber of the

VVU Biogas facility. The effluent was collected into 40 L plastic gallons and transported

to the greenhouse at the Botany Department of the University of Ghana.

29

2.9.2 Slow Sand filtration (SSF)

2.9.2.1 Preparation of filter media

Three plastic buckets each of 100 cm height and 100 L capacity were prepared, each with

a tap fitted at the bottom to allow filtered effluent to be drained out. Two of the buckets

were used to filter the raw sewage effluent and the third was used as a control. Each

bucket was filled with gravel of 5-10 cm diameter at the bottom, coarse river sand of 2-3

mm diameter as mid layer each of 10 cm depth and fine river sand of 0.4 mm diameter at

40 cm depth. A diffusion plate was placed 10 cm above the fine sand to allow even

distribution of the raw sewage effluent on the surface of the fine sand.

Plate 5: Slow Sand Filtration experimental set up at the greenhouse

30

Fig 2: Cross-section of slow sand filter media for Slow Sand Filtration of effluent

10cm

10cm

m

40cm

Diffusion plate

Fine sand (0.4mm)

Coarse sand (2 – 3mm)

Gravels (2 – 5mm)

31

2.9.2.2 Procedure for slow sand filtration of raw effluent

Effluent was carefully poured from a bucket and allowed to percolate through the filter

media. A water column of about 10 cm height was maintained above the sand to provide

the needed pressure force to move the water through the sand bed system. The procedure

was repeated for the control using distilled water. The rate of filtration through the filter

media was determined weekly by measuring the volume of effluent per minute. Filtration

was done once every week for ten weeks.

Effluent samples and water for the control were analyzed for their various physico-

chemical and microbiological characteristics before sand filtration and filtered effluents

were also analyzed on a weekly basis for ten weeks using standard methods

2.10 Phytoremediation

2.10.1 Layout of the experiment

The design of the experiment was a completely randomized. Two different macrophytes,

namely Ipomoea aquatica and Pistia stratiotes were used. These plants were selected

because they are readily available.There were two replicates each and one control unit

using distilled water.

Trial experiments were conducted to ascertain the performance of the plants in the

sewage effluent. Two bowls of 40 L capacities were each filled with sewage effluent and

the ten each of the plants, previously rinsed with tap water were planted in the bowls. In

each bowl, twenty each of the individual plants were planted. Plant growth was observed.

32

For the actual experimental set up, Pistia stratiotes and Ipomoea aquatica plants

collected from the Kpong Head Pond were rinsed and transferred into a large bowl

containing tap water. Samples of the whole plants were oven dried at 105°C for 10 hours,

ground into powder, digested and analyzed for the nutrient content.

For each of the plants, two plastic bowls were each filled with sewage effluent to a height

of 16 cm and kept outside in the open air. A third bowl was filled with distilled water to

serve as a control.

Each plant was then put in the bowls and one week was allowed for the plants to

acclimatize to their new environment. It was observed during the first week that the Pistia

stratiotes showed signs of wilting after the fifth day. Therefore, water samples from

effluent treated with Ipomoea aquatica and Pistia stratiotes were taken after the fifth day

for analyses. Starting from the second week, samples of water from effluent treated with

Ipomoea aquatica were collected on a weekly basis for four weeks and analyzed for the

physico-chemical and microbiological characteristics. At the end of the experimental

period (five days for Pistia stratiotes and four weeks for Ipomoea aquatica), samples of

the whole plant were taken from each bowl, oven dried, ground into powder, digested and

analyzed to determine the nutrient and heavy metal content.

Dilutions of the effluent (50% and 75%) were also prepared for planting Pistia stratiotes.

This was done to determine whether Pistia stratiotes would survive for more than five

days in the diluted effluent.

The experiment was conducted in open air under natural daylight regime.

33

A B C

Plate 6: Pistia stratiotes in different dilutions of effluent

A- Pistia stratiotes in 50% dilution of effluent, B- Pistia stratiotes in 75% dilution of

effluent, C- Pistia stratiotes in distilled water (control)

Plate 7: Ipomoea aquatica planted in sewage effluent

34

2.11 Laboratory analyses

Physico-chemical analyses were carried out at the Ecological Laboratory of the

University of Ghana. Bacteriological analyses for Total coliforms, Total Heterotrophic

Bacteria (THB) and faecal coliforms were undertaken at the Microbiological Laboratory

at the Soil Science Department of the University of Ghana. The physico-chemical

parameters determined included pH , temperature, conductivity, turbidity, dissolved

oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD),

total suspended solids (TSS), total dissolved solids (TDS), colour, phosphate and nitrate.

2.11.1 Physico-chemical analyses of raw and treated effluents

The physico-chemical parameters were determined according to procedures outlined in

the Standard Methods for the Examination of Water and Wastewater. At the sampling

site, the effluent was collected into a plastic bucket for in-situ measurements.

Temperature, pH and conductivity were measured using a digital meter (Model YSI 63),

turbidity was measured using turbidimeter (Model HACH 2100P) NTU and Total

Dissolved Solids (TDS) was measured with a portable digital TDS meter (Model HI

99301).

2.11.2 Total Suspended Solids Analysis

The photometric (non-filterable residue) method was used. Five hundred millilitres of

sample was blended at high speed for two minutes. This was poured into a 600 ml beaker.

The sample was stirred and 25 ml immediately poured into a sample cell. The stored

programme number for suspended solids, 630, was set to a wavelength of 810 nm. A

35

sample cell filled with 25 ml distilled water served as blank. This was placed into the cell

holder and standardized. The sample was placed into the cell holder and the reading taken

in mg/l suspended solids.

2.11.3 Heavy Metal Analysis

The Atomic Absorption Spectrometry (AAS) method for heavy metals was used to

determine the level of each heavy metal in the sample. The heavy metals whose

concentrations were determined included: Cadmium (Cd), Copper (Cu), Nickel (Ni), Zinc

(Zn), Lead (Pb), Iron (Fe) and Chromium (Cr).

In flame atomic absorption spectrometry, a sample is aspirated into a flame and atomized.

A light beam is directed through the flame, into a monochromator, and onto a detector

that measures the amount of light absorbed by the atomized element in the flame.

For some metals, atomic absorption exhibits superior sensitivity over flame emission.

Because each metal has its own characteristic absorption wavelength, a source lamp

composed of that element is used; this makes the method relatively free from spectral or

radiation interferences.

The amount of energy at the characteristic wavelength absorbed in the flame is

proportional to the concentration of ion in the sample over a limited concentration range.

36

2.11.4 Dissolved Oxygen (DO)

The azide modification of the Winkler method was used for this test. Two milliliter conc.

H2SO4 was added to the samples which had already been fixed on the field with 2 ml

each of Winkler 1 (Manganous chloride) and Winkler 2 (alkaline-iodide-azide reagent).

One hundred milliliters of the sample was titrated with 0.025 M Na2S2O3 to a pale straw

colour. Two milliliters of starch solution was added and titration was continued to first

disappearance of blue colour.

Calculation:

For titration of a 100 ml sample, mg/l mg/l O2 = Vol. of M/80 thiosulphate used x 101.6

Vol. of sample used

2.11.5 Biological Oxygen Demand (BOD)

The 5-day BOD test was used. Biochemical Oxygen Demand, or BOD, measures the

amount of oxygen consumed by microorganisms in decomposing organic matter in

stream water. BOD also measures the chemical oxidation of inorganic matter (i.e. the

extraction of oxygen from water via chemical reaction). A test is used to measure the

amount of oxygen consumed by these organisms during a specific period of time (usually

5 days at 20oC).This method consists of filling with sample an airtight bottle of the

specific size and incubating it at the specific temperature for 5 days. Dissolved oxygen

was measured initially and after incubation, and the BOD was computed from the

difference between the initial and the final DO. In cases of dilution due to less amount of

oxygen, BOD was computed from the formula below:

37

Calculation: BOD5 mg/l = D1 – D2

P

Where;

D1 = DO of diluted sample immediately after preparation, mg/l

D2 = DO of diluted sample after 5 day incubation at 20 0C, mg/l

P = Decimal Volumetric fraction of sample used.

2.11.6 Nitrogen-Nitrate (NO3- -N) Analysis

The Cadmium Reduction Method using Powder Pillows was used for the determination

of nitrogen nitrate. The nitrate level in each sample was measured using Nitrate Powder

Pillows in a direct reading Hach Spectrophotometer (Model DR 2000). Twenty five (25)

ml of the sample was measured into sample cell of the spectrophotometer. One Nitraver 5

Nitrate Reagent Powder Pillow was added to the sample. The mixture was then shaken

vigorously for 1 minute. Five minutes was allowed for the solution to react. An orange

colour of the mixture indicates the presence of nitrate. After five minutes, another cell

was filled with 25 ml of only the sample (blank). The blank sample was placed in the

Spectrophotometer for calibration. The prepared sample was placed into the cell holder to

determine the nitrate concentration at 500 nm in mg/l .

2.11.7 Phosphate (PO43-) Analysis

A 25 ml of the prepared water sample was placed in the sample cell. PhosVer 3

Phosphate Powder Pillow was added to the cell content and swirled immediately to mix.

38

A two-minute reaction period was allowed. A blue colouration of the mixture indicates

the presence of phosphate. Another sample cell (the blank) was filled with 25 ml of

sample and placed into the cell holder to calibrate it. After reaction period, the prepared

sample was placed into the cell holder and the level of phosphorus was determined at 890

nm.

2.11.8 Chemical Oxygen Demand (COD)

A sample of sewage effluent (50 ml) was pipetted into a 500 ml refluxing flask. One

gram of mercuric sulphate was added to the sample and several glass beads were added to

the solution. Very slowly, 5 ml of sulphuric acid reagent was added and the flask was

swirled while adding the reagent to help dissolve the mercuric sulphate. Twenty five

millilitres of 0.250 N potassium dichromate solution was added and mixed. Distilled

water was used as the blank.The sample flask and blank flask were refluxed after which

the sample and blank were titrated with ferrous ammonium sulphate using ferroin

indicator. The COD was calculated using the following formula:

COD mg/l = (A-B) ×M×8,000

Volumeof sample, ml

Where:

A=ml of titrant used for sample

B= ml of titrant used for blank

M=normality of ferrous ammonium sulphate

39

2.11.10 Analyses of Bacteriological Parameters of raw and treated effluents

Bacteriological analyses involved the determination of total Heterotrophic Bacteria

(THB), Total Coliforms and Faecal Coliforms by the membrane filtration method. These

parameters were determined only for the raw effluent and for the effluents at the end of

the experiment.

2.11.10.1 Preparation of bacteriological media for bacteriological analyses of raw

and treated effluents

Preparation of Hicrome coliform agar

Hicrome coliform agar was used. It is a selected medium recommended for the

simultaneous detection of faecal coliforms and total coliforms in water and food samples.

Twenty eight grams (28 g) of the powder was weighed and dissolved in 1 litre of

deionized water. It was swirled to mix, sterilized by autoclaving for 15 min at 121ºC,

cooled to 47ºC and poured into petri dishes.

Preparation of nutrient agar

Twenty eight grams of the dehydrated nutrient agar powder was weighed and dispensed

in 1 litre of deionized water. The solution was allowed to soak for 10 min and sterilized

by autoclaving for 15 min at 121ºC. It was allowed to cool to 47ºC and stored in the

refrigerator.

40

Membrane Filtration Method

The filter holding assembly constructed of stainless steel and consisted of a seamless

funnel fastened to a base by a locking device. The design permitted the membrane filter

to be held securely on the porous plate of the receptacle without mechanical damage and

allowed all fluid to pass through the membrane during the filtration process. Firstly, the

receptacle was sterilized with 96% alcohol, flamed and allowed to cool. A membrane

filter of pore size 0.45 µm was gently placed on it and a filter funnel fitted unto it.

Twenty millilitres (20 ml) of the effluent samples were diluted with distilled water,

poured unto the funnel and extracted through a side tube, such that pressure could be

exerted on the membrane filter. The filter was picked gently using sterilized forceps and

placed in a petri dish containing sterilized Hicrome Coliform agar for the enumeration of

total coliforms and faecal coliforms. Another filter was placed on nutrient agar for the

enumeration of total heterotrophic bacteria. After incubation on Hicrome Coliform Agar

for 24 hours at 35ºC to 37ºC, faecal coliforms appeared dark violet. Other colonies were

counted for total heterotrophic bacteria.

The Total and Faecal coliform present in water samples were determined using the

Membrane Filter (MF) technique. Membrane filter with 0.45 µm pore size was sterilized

in a system and used to filter 100 ml of water mixed with 10 ml of the sampled water.

The results obtained from the colony counting were then multiplied by 10 to obtain the

actual count per 100 ml for faecal and total coliforms

M-Lauryl sulphate broth (LSB) was used as growth medium for the incubation of

coliforms in a petri dish. Two milliliters of the broth was poured on an absorptive pad

placed in a small Petri dish. The petri dish was then covered and inverted into ELE

41

paqualab incubator (model 50) for incubation at 37oC for total coliform and 44oC for

faecal coliform. After 24 hours, the Petri dishes were removed from the incubator and the

colonies counted and recorded in coliform forming units per 100 ml (cfu/100 ml)

2.12 Social survey

Questionnaire Administration

Questionnaires were administered to 120 randomly selected respondents. One hundred

and twenty respondents from among students and staff of the Valley View University

were selected due to the limited time for the study. During the time of the study, the

University was on vacation so there were few people on the University campus and this

accounted for the few number of respondents. One hundred and two questionnaires were

returned and the data was coded and analysed using SPSS version 20.

2.13 Statistical analyses

All data generated were double entered and cross checked for anomalies. The data was

transferred into SPSS version 20. Comparison of phytoremediation and Slow Sand

Filtration technologies was done using one-way ANOVA. The mean and percentage

increase/ reduction were calculated for each parameter using Microsoft Excel. The

questionnaires were analyzed using Statistical Package for Social Science (SPSS) version

20.

42

CHAPTER THREE

3.0 RESULTS

The results of the study are shown below

3.1 Quality of sewage effluent from VVU biogas facility

Table 1: Quality of sewage effluent from intermediary chamber (A) and final outlet

(B) of the Valley View University (VVU) Biogas facility.

Parameters analysed A B

p H 3.9-4.14 6.47-7.48

Temperature (°C) 29.2-32.4 25.2-30.3

Electrical conductivity (µs/cm) 5017-5420 3216-3603

Total dissolved solids (mg/l) 2508.5-2710 1608-1801.5

Total suspended solids (mg/l) 322-368 56-75

Colour (PtCo) 699-792 487-543

Phosphates (mg/l) 4.3-6.4 0.44-5.6

Nitrates (mg/l) 1.7-4.2 1.8-9.7

Dissolved oxygen (mg/l) 0.11-0.6 2.98-5.4

Biochemical Oxygen Demand (mg/l) 29-40 17-35

Chemical Oxygen Demand (mg/l) 224-368 64-132

Turbidity (NTU) 121-201 42-53

Zinc ND ND

Lead ND ND

Copper 0.11 0.11

Iron 0.413 0.231

Cadmium ND ND

Nickel ND ND

Chromium ND ND

Total heterotrophic bacteria (CFU/ml) 1210 1124

Total coliforms (CFU/100ml) 348 322

Faecal coliforms(CFU/100ml) 162 101

*ND: Non Detectable; A- raw effluent from intermediary chamber; B- effluent from final

outlet

The table 1 above presents detailed results of the quality of effluent from the intermediary

chamber (A) and final outlet (B) of the Valley View University Biogas facility

43

3.2 Phytoremediation using Pistia stratiotes and Ipomoea aquatica

Plant growth in raw sewage effluent

(A) (B) (C)

Plate 8: Condition of Pistia stratiotes days after planting in sewage effluent

A above represents fresh and healthy Pistia stratiotes planted in the raw sewage effluent

on the first day. Three days after planting, the plants had started wilting as shown in B

and after the fifth day all the plants had wilted (C).

A B C D

Plate 9: Condition of Ipomoea aquatica days after planting in sewage effluent

44

A above shows Ipomoea aquatica plants on the first day of planting in the raw sewage

effluent. By the third day (B), new shoots had started coming out. C and D show the

growth of the plants on the fifth and fourteen days respectively.

A B

Plate 10: Sewage effluent before (A) and after treatment (B) with Pistia stratiotes

A above is the raw sewage effluent before phytoremediation. It can be seen that some

level of treatment occurred after phytoremediation with Pistia stratiotes. The treated

effluent (B) looks clearer and less turbid than the raw effluent (A).

45

b a

Plate 11: Sewage effluent before (a) and after treatment (b) with Ipomoea aquatica

Comparing the effluent before and after treatment with Ipomoea aquatica, it can be seen

that, some purification has taken place. The treated effluent looks clearer than the raw

effluent.

46

3.3 Nitrogen and phosphorus uptake by plants

Table 2: Phosphorus and nitrogen accumulation in Ipomoea aquatica and Pistia

stratiotes at the end of experiment

Total nitrogen (%) Total phosphorus (%)

P.S I.A P.S I.A

Before the experiment 2.996 2.604 0.92 0.77

After the experiment 3.332 3.892 1.17 1.19

Percentage increase (%) 10.08 33.09 21.37 35.29

*P.S – Pistia stratiotes I.A – Ipomoea aquatica

The table above show the nitrogen and phosphorus content of Ipomoea aquatica and

Pistia stratiotes before and after the phytoremediation experiment. The results show that

both plants took up nitrogen and phosphorus. Ipomoea aquatica took up more nitrogen

and phosphorus than Pistia stratiotes.

47

3.4 Contaminant removal efficiency of Ipomoea aquatica and Pistia stratiotes

0

2

4

6

8

10

12

14

16

18

Pistia stratiotes Ipomoea aquatica

Ph

osp

hat

e R

em

ova

l e

ffic

ien

cy (

%)

Aquatic macrophyte

Fig 3: Phosphate removal efficiency of Ipomoea aquatica and Pistia stratiotes

0

20

40

60

80

100

120

Pistia stratiotes Ipomoea aquatica

Nit

rate

re

mo

val

eff

icie

ncy

(%

)

Aquatic macrophyte

Fig 4: Nitrate removal efficiency of Ipomoea aquatica and Pistia stratiotes

48

0

10

20

30

40

50

60

Pistia stratiotes Ipomoea aquatica

CO

D r

em

ova

l e

ffic

ien

cy (

%)

Aquatic macrophyte

Fig 5: COD removal efficiency of Ipomoea aquatica and Pistia stratiotes

0

10

20

30

40

50

60

Pistia stratiotes Ipomoea aquatica

EC r

em

ova

l eff

icie

ncy

(%

)

Aquatic macrophyte

Fig 6: EC removal efficiency of Ipomoea aquatica and Pistia stratiotes

49

The figures 3,4,5, and 6 show that both plants were effective at reducing contaminant

levels. However, Ipomoea aquatica reduced phosphate (16.07%), nitrates (100%) and

COD (47.8%) to lower levels whilst Pistia stratiotes reduced electrical conductivity (EC)

to lower levels (55.45%) (Fig 6) than did Ipomoea aquatica.

3.5 Weekly variations in water quality parameters after treatment with Ipomoea

aquatica

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

1 2 3 4 5

DO

(m

g/l)

Duration of experiment (week)

Fig 7: Concentration of dissolved oxygen (DO) in effluent after every week of

treatment with Ipomoea aquatica

50

0

5

10

15

20

25

30

35

40

1 2 3 4 5

BO

D (

mg/

l)

Duration of study (week)

Fig 8: Biochemical Oxygen Demand (BOD) of effluent after every week of treatment

with Ipomoea aquatica

0

50

100

150

200

250

300

350

400

1 2 3 4 5

CO

D(m

g/l)

Duration of experiment (week)

Fig 9: Chemical Oxygen Demand (COD) of effluent after every week of treatment

with Ipomoeaaquatica

51

0

1000

2000

3000

4000

5000

6000

1 2 3 4 5

EC (

µs/

Cm

)

Duration of experiment (week)

Fig 10: Electrical conductivity (EC) of effluent after every week of treatment with

Ipomoea aquatica

0

500

1000

1500

2000

2500

3000

1 2 3 4 5

TDS

(mg/

l)

Duration of experiment (week)

Fig 11: Total Dissolved Solids (TDS) of effluent after every week of treatment with Ipomoea

aquatica

52

0

2

4

6

8

10

1 2 3 4 5

PO

4 (

mg/

l)

Duration of experiment (week)

Fig 12: Concentration of phosphates in effluent after every week of treatment with

Ipomoea aquatica

0

5

10

15

20

25

30

35

40

1 2 3 4 5

NO

3 (

mg/

l)

Duration of experiment (week)

Fig 13: Concentration of nitrates in effluent after every week of treatment with

Ipomoea aquatica

53

3.6 Performance of Slow Sand Filtration

Fig 14 below shows a decreasing rate of filtration of the raw effluent through the

experimental sand filter. Figures 15, 16, 17, 18, 22 and 23 show a decreasing trend in

turbidity, electrical conductivity (EC), total dissolved solids (TDS), total suspended

solids (TSS), Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand

(COD) respectively. The concentration of nitrates (Fig 19) decreased after first week and

increased from the second to fifth week after which it decreased till the tenth week.

Phosphate concentration (Fig 20) decreased from start of the experiment to the fourth

week after which it increased from the fifth to sixth week and decreased again from the

seventh to tenth week. Fig 21 shows an increase in dissolved oxygen (DO) after the first

week. It decreased after the second to the seventh week and then increased again to the

end of the experiment.

0

100

200

300

400

500

600

700

800

1 2 3 4 5 6 7 8 9 10 11

Filt

rati

on

rat

e (

ml/

min

)

Time (week)

Fig 14: Rate of filtration through experimental sand filter

54

0

20

40

60

80

100

120

140

160

180

1 2 3 4 5 6 7 8 9 10 11

TUR

BID

ITY

(N

TU)

Time (week)

Fig 15: Weekly variations in turbidity of effluent treated using SSF method

0

1000

2000

3000

4000

5000

6000

1 2 3 4 5 6 7 8 9 10 11

EC (

µs/

CM

)

Time (week)

Fig 16: Weekly variations in electrical conductivity (EC) of effluent treated using

SSF

55

0

500

1000

1500

2000

2500

3000

1 2 3 4 5 6 7 8 9 10 11

TDS

(mg/

l)

Time (week)

Fig 17: Weekly variations in concentration of total dissolved solids (TDS) in effluent

treated using SSF

0

2

4

6

8

10

12

1 2 3 4 5 6 7 8 9 10 11

nit

rate

s (m

g/l)

Time (week)

Fig 18: Weekly variations in concentration of Total Suspended Solids (TSS) in effluent

treated using SSF

56

0

1

2

3

4

5

6

1 2 3 4 5 6 7 8 9 10 11

Ph

osp

hat

es (

mg/

l)

Time (week)

Fig 19: Weekly variations in concentration of nitrates in effluent treated using SSF

Fig 20: Weekly variations in concentration of phosphates in effluent treated using

SSF

0

50

100

150

200

250

1 2 3 4 5 6 7 8 9 10 11

TSS

(mg/

l)

Time (week)

57

0

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8 9 10 11

DO

(m

g/l)

Time (week)

Fig 21: Weekly variations in concentration of dissolved oxygen in effluent treated

using SSF

0

5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 8 9 10 11

BO

D (

mg/

l)

Time (week)

Fig 22: Weekly variations in Biochemical Oxygen Demand (BOD) of effluent treated

using SSF

58

0

50

100

150

200

250

300

350

400

1 2 3 4 5 6 7 8 9 10 11

CO

D (

mg/

l)

Time (week)

Fig 23: Weekly variations in Chemical Oxygen Demand (COD) of effluent treated

using SSF

A B

Plate 12: Sewage effluent before (A) and after seventh week (B) of slow sand

filtration

59

It can be clearly seen that the effluent has been purified to a great extent. The treated

effluent looks clearer than the raw effluent (A).

3.7 Comparison of phytoremediation using Ipomoea aquatica and slow sand

filtration (SSF) technologies

One-way analysis of variance was employed in testing the hypotheses assuming normal

distribution with equal variance: Ho: mus=mui=musc=muic. H1: The mean values are all

not the same.

60

Table 3: Comparison of p H of effluent treated using SSF with effluent from

treatment with Ipomoea aquatica

Ph Week SSF Ipomoea

aquatica

Scontrol Icontrol

0 4.130 4.14 7.32 7.72

1 6.540 7.38 6.91 6.45

2 6.515 7.22 6.63 6.06

3 7.585 7.77 6.80 6.75

4 7.165 7.65 7.10 7.19

PH ANOVA Sum of Source DF Squares Mean Square F Value Pr> F Model 3 0.93173375 0.31057792 0.27 0.8457 Error 16 18.37221000 1.14826312 Corrected Total 19 19.30394375 R-Square CoeffVar Root MSE Water Mean 0.048266 15.87218 1.071570 6.751250 Source DF Anova SS Mean Square F Value Pr> F Group 3 0.93173375 0.31057792 0.27 0.8457

The ANOVA for the pH table shows that the means of all the water treatment methods

are the same. Therefore, it does not matter which water treatment method is employed

they will both yield the same results since we fail to reject the null hypothesis. The

Scheffe's Test and Student-Newman-Keuls Test also show that the means of the water

treatment method on pH are all not significantly different. This implies that both

treatment methods are effective at changing acidic conditions to neutral.

61

Table 4: Comparison of the concentration of dissolved oxygen (DO) of effluent

treated using SSF with effluent treated with Ipomoea aquatica

DO (mg/l) Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 1.935 0.17 6.0 6.3

1 6.100 2.10 5.5 4.3

2 5.100 3.50 4.6 4.8

3 4.250 1.90 5.3 5.5

4 3.700 4.10 4.5 6.7

DO (mg/l) ANOVA The ANOVA Procedure Dependent Variable: Water Sum of Source DF Squares Mean Square F Value Pr> F Model 3 30.27672375 10.09224125 6.51 0.0044 Error 16 24.79960000 1.54997500 Corrected Total 19 55.07632375 R-Square CoeffVar Root MSE Water Mean 0.549723 28.83400 1.244980 4.317750 Source DF Anova SS Mean Square F Value Pr> F Group 3 30.27672375 10.09224125 6.51 0.0044 Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 1.549975 Number of Means 2 3 4 Critical Range 1.6692018 2.0317383 2.2527514 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 5.5200 5 ic A A 5.1800 5 sc A A 4.2170 5 s B 2.3540 5 i

Since the p value (0.0044) of the F calculated from the DO ANOVA is less than the

significant level (0.05), there is enough evidence against the null hypothesis and it can be

62

concluded that the means are all not the same. The analysis shows that the water

treatment methods on DO (mg/l) are not the same. Therefore, Multiple Comparisons or

Post Hoc analysis was performed since the means are not the same. The Scheffe's Test

and Student-Newman-Keuls Test revealed that the treatment with Ipomoea aquatica was

the best in this case since it has the higher mean for DO (mg/l). Water with a higher DO

concentration is evident of lower contamination by aerobic microorganism and therefore

more desirable.

63

Table 5: Comparison of turbidity of effluent treated using SSF with effluent from

treatment with Ipomoea aquatica

TURBIDITY

(NTU)

Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 159.50 143.0 0.8 4.00

1 119.00 147.0 1.1 2.18

2 12.50 20.2 1.0 5.40

3 10.95 54.0 1.0 1.80

4 9.75 12.9 1.0 6.30

Turbidity ANOVA Sum of Source DF Squares Mean Square F Value Pr> F Model 3 22508.97126 7502.99042 3.19 0.0523 Error 16 37664.08492 2354.00531 Corrected Total 19 60173.05618 R-Square CoeffVar Root MSE Water Mean 0.374071 136.0231 48.51809 35.66900 Source DF Ano va SS Mean Square F Value Pr> F Group 3 22508.97126 7502.99042 3.19 0.0523 Scheffe's Test for Water Treatment NOTE: This test controls the Type I experiment wise error rate. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 2354.005 Critical Value of F 3.23887 Minimum Significant Difference 95.651 Means with the same letter are not significantly different. Scheffe’s Grouping Mean N Group A 75.42 5 i A A 62.34 5 s A A 3.94 5 ic A A 0.98 5 sc

64

The analysis of the turbidity data shows that there is no evidence against the null

hypothesis since the p-value (0.0523) is greater than the significant level (0.05). Hence,

we fail to reject the null hypothesis and conclude that all the means of the treatment

methods are the same. Post hoc analysis also confirms this assertion. This implies

turbidity of the water would not be significantly different irrespective of the treatment

method used.

65

Table 6: Comparison of EC of effluent treated with SSF with effluent from

treatment with Ipomoea aquatica

EC (µs/CM)

Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 5413.5 5365 347 309

1 3755.0 3122 345 287

2 3398.0 3105 326 276

3 2859.0 3075 355 255

4 2813.0 2030 352 231

EC (us/CM) ANOVA

Sum of Source DF Squares Mean Square F Value Pr> F Model 3 50980178.94 16993392.98 25.88 <.0001 Error 16 10504475.20 656529.70 Corrected Total 19 61484654.14 R-Square CoeffVar Root MSE Water Mean 0.829153 42.62479 810.2652 1900.925 Source DF Anova SS Mean Square F Value Pr> F Group 3 50980178.94 16993392.98 25.88 <.0001 EC (us/CM) ANOVA The ANOVA Procedure Student-Newman-Keuls Test NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 656529.7 Number of Means 2 3 4 Critical Range 1086.3598 1322.308 1466.149 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 3647.7 5 s A A 3339.4 5 i B 345.0 5 sc B B 271.6 5 ic

The EC (mg/l) data shows enough evidence that the means are all not the same since the

p-value (0.0001) of the calculated F value is less than the significant level (0.05). In view

66

of this, Post Hoc analysis was conducted to ascertain how different they are. From the

Student-Newman-Keuls Test, sand filtration method of water treatment is not

significantly different from that of treatment with Ipomoea aquatica. However, since the

mean of the sand filtration method on EC (mg/l) is higher than that of Ipomoea aquatica,

it follows that phytoremediation with Ipomoea aquatica is better in this case than the

sand filtration.

67

Table 7: Comparison of concentration Total Dissolved Solids (TDS) of effluent

treated using SSF with effluent from treatment with Ipomoea aquatica

TDS (mg/l) Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 2706.75 2683.0 173.5 154.5

1 1877.50 1901.0 172.5 143.5

2 1699.00 1552.5 163.0 138.0

3 1429.50 1537.5 177.5 127.5

4 1406.50 1015.0 176.0 115.5

TDS (mg/l) ANOVA Sum of Source DF Squares Mean Square F Value Pr> F Model 3 13252236.51 4417412.17 26.72 <.0001 Error 16 2645627.80 165351.74 Corrected Total 19 15897864.31 R-Square CoeffVar Root MSE Water Mean 0.833586 42.02996 406.6346 967.4875 Source DF Anova SS Mean Square F Value Pr> F Group 3 13252236.51 4417412.17 26.72 <.0001

Scheffe's Test NOTE: This test controls the Type I experiment wise error rate. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 165351.7 Critical Value of F 3.23887 Minimum Significant Difference 801.66 Means with the same letter are not significantly different. Scheffe’s Grouping Mean N Group A 1823.9 5 s A A 1737.8 5 i B 172.5 5 sc B B 135.8 5 ic

The analysis of the TDS (mg/l) data shows that there is enough evidence against the null

hypothesis in favour of the alternate one. Since the p-value (0.0001) of the F calculated is

less than the significance level (0.05), there is sufficient ground to say that the water

68

treatment methods do not produce same results. The multiple comparisons of the methods

using Student-Newman-Keuls Test shows that sand filtration and treatment with Ipomoea

aquatica are not significantly different. However, treatment with Ipomoea aquatica

reduces TDS better than sand filtration since the mean of the former is less than that of

the latter.

69

Table 8: Comparison of concentration of Total Suspended solids (TSS) of effluent

treated using SSF with effluent from treatment with Ipomoea aquatica

TSS (mg/l) Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 238.0 239 8 6

1 221.5 315 6 23

2 21.0 35 6 10

3 18.0 70 6 3

4 14.0 31 5 15

TSS (mg/l) ANOVA The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 65323.7375 21774.5792 2.84 0.0708 Error 16 122602.0000 7662.6250 Corrected Total 19 187925.7375 R-Square CoeffVar Root MSE Water Mean 0.347604 135.6628 87.53642 64.52500 Source DF Anova SS Mean Square F Value Pr> F Group 3 65323.73750 21774.57917 2.84 0.0708 TSS (mg/l) ANOVA The ANOVA Procedure Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 7662.625 Number of Means 2 3 4 Critical Range 117.3641 142.85459 158.39436 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 138.00 5 i A A 102.50 5 s A A 11.40 5 ic A A 6.20 5 sc

On the analysis of the TSS (mg/l), the p-value (0.0708) of the F calculated is greater than

the level of significance (0.05), hence we have insufficient evidence to reject the null

70

hypothesis and conclude that the means of the water treatment methods on the chosen

parameter are the same. Therefore, it does not matter whether sand filtration or

phytoremediation with Ipomoea aquatica method is used since both will yield the same

result . The mean of treatment with Ipomoea aquatica method on TSS (mg/l) is greater

than that of sand filtration method even though they are not significantly different. Thus

sand filtration is a better method for the removal of suspended solids.

71

Table 9: Comparison of colour of effluent treated using SSF with effluent from

treatment with Ipomoea aquatica

COLOUR (PtCo) Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 731 738 7 21

1 565 218 5 20.1

2 234 718 4 19

3 217 664 4 15

4 210 334 4 10.4

Colour ANOVA The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 1072794.737 357598.246 12.28 0.0002 Error 16 465872.320 29117.020 Corrected Total 19 1538667.058 R-Square CoeffVar Root MSE Water Mean 0.697223 72.02157 170.6371 236.9250 Source DF Anova SS Mean Square F Value Pr> F Group 3 1072794.738 357598.246 12.28 0.0002 Colour ANOVA The ANOVA Procedure Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 29117.02 Number of Means 2 3 4 Critical Range 228.781 278.4703 308.76238 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 534.4 5 i A A 391.4 5 s B 17.1 5 ic B B 4.8 5 sc

The colour analysis of the water treatment methods is significantly different since the p-

value of the F calculated (0.0002) is less than the level of significance (0.05). According

72

to the Post Hoc analysis of the same data, phytoremediation and sand filtration methods

of water treatment are not significantly different. This implies that they may yield the

same result on the colour of the water. However, the mean of the phytoremediation

method on colour is greater than that of sand filtration, hence rendering the method of

sand filtration better at reducing colour.

73

Table 10: Comparison of concentration of nitrates in effluent treated using SSF with

effluent treated using Ipomoea aquatica

NO3 (mg/l) Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 2.65 3.2 3.5 0.5

1 1.70 0.0 1.3 0.2

2 8.45 3.4 1.0 0.0

3 9.40 1.4 1.3 0.8

4 10.70 33.6 1.5 0.3

NO3 (mg/l) The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 949361.350 316453.783 10.37 0.0005 Error 16 488479.200 30529.950 Corrected Total 19 1437840.550 R-Square CoeffVar Root MSE Water Mean 0.660269 69.15821 174.7282 252.6500 Source DF Anova SS Mean Square F Value Pr> F Group 3 949361.3500 316453.7833 10.37 0.0005 NO3 (mg/l) The ANOVA Procedure Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 30529.95 Number of Means 2 3 4 Critical Range 234.26615 285.14678 316.16513 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 534.4 5 i A A 391.4 5 s B 80.0 5 ic B B 4.8 5 sc

74

The NO3- data also shows enough evidence against the null hypothesis in favour of the

alternative implying that the means are all significantly different. This is because the p-

value of the F calculated (0.0005) is less than the level of significance (0.05). The

treatment methods have effects on the NO3 of water. Post Hoc analysis shows that sand

filtration is better at reducing nitrate concentration even though the means are not

significantly different.

75

Table 11: Comparison of phosphate concentration in effluent treated using SSF with

effluent from treatment with Ipomoea aquatica

PO4 (mg/l) Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 5.470 5.60 1.44 1.70

1 3.550 4.70 1.14 0.20

2 3.030 3.90 1.09 0.10

3 2.810 5.64 2.49 1.20

4 3.350 8.24 2.54 7.04

PO4 (mg/l) The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 949361.350 316453.783 10.37 0.0005 Error 16 488479.200 30529.950 Corrected Total 19 1437840.550 R-Square CoeffVar Root MSE Water Mean 0.660269 69.15821 174.7282 252.6500 Source DF Anova SS Mean Square F Value Pr> F Group 3 949361.3500 316453.7833 10.37 0.0005

Scheffe's Test NOTE: This test controls the Type I experiment wise error rate. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 30529.95 Critical Value of F 3.23887 Minimum Significant Difference 344.47 Means with the same letter are not significantly different. Scheffe’s Grouping Mean N Group A 534.4 5 i A B A 391.4 5 s B B C 80.0 5 ic C C 4.8 5 sc

There is enough evidence against the null hypothesis in favour of the alternative since the

p-value of the F calculated (0.0005) is less than the level of significance (0.05). This

76

implies that the means are all significantly different and sand filtration seems to be better

at reducing phosphate concentration than phytoremediation with Ipomoea aquatica.

77

Table 12: Comparison of Biochemical Oxygen Demand (BOD) of effluent treated

with SSF with effluent from treatment with Ipomoea aquatica

BOD (mg/l) Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 35.00 35.0 6.2 6.2

1 25.00 16.0 4.5 4.3

2 21.50 15.1 0.9 3.2

3 11.00 18.0 0.2 1.8

4 8.50 4.1 0.2 0.9

BOD (mg/l) The ANOVA Procedure Sum of Source DF Squares Mean Square F Value Pr> F Model 3 1301.869500 433.956500 6.90 0.0034 Error 16 1006.380000 62.898750 Corrected Total 19 2308.249500 R-Square CoeffVar Root MSE Water Mean 0.564007 73.06194 7.930873 10.85500 Source DF Anova SS Mean Square F Value Pr> F Group 3 1301.869500 433.956500 6.90 0.0034 BOD (mg/l) 27 Student-Newman-Keuls Test for Water NOTE: This test controls the Type I experiment wise error rate under the complete null hypothesis but not under partial null hypotheses. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 62.89875 Number of Means 2 3 4 Critical Range 10.633286 12.942746 14.350662 Means with the same letter are not significantly different. SNK Grouping Mean N Group A 20.100 5 s A A 17.640 5 i B 3.280 5 ic B B 2.400 5 sc

78

The BOD analysis shows that all the means are significantly different since the F test is in

favour of the alternative hypothesis. Since the F calculated p-value (0.0034) is less than

the significant level (0.05), there is enough evidence against the null hypothesis. In view

of this, multiple comparison analysis revealed that sand filtration and phytoremediation

with Ipomoea aquatica have mean values that are not significantly different. But the

mean BOD of water treated with Ipomoea aquatica is greater than that of sand filtration

implying making sand filtration a better method at reducing BOD.

79

Table 13: Comparison of Chemical Oxygen Demand (COD) of effluent treated using

SSF with effluent from treatment with Ipomoea aquatica

COD (mg/l)

Week SSF Ipomoea

Aquatica

Scontrol Icontrol

0 368 368 256 256

1 288 192 224 160

2 240 160 192 128

3 176 96 160 64

4 144 64 128 32

The ANOVA

Sum of Source DF Squares Mean Square F Value Pr> F Model 3 33830.4000 11276.8000 1.40 0.2802 Error 16 129228.8000 8076.8000 Corrected Total 19 163059.2000 R-Square CoeffVar Root MSE Water Mean 0.207473 48.63150 89.87102 184.8000 Source DF Anova SS Mean Square F Value Pr> F Group 3 33830.40000 11276.80000 1.40 0.2802 Scheffe's Test for Water NOTE: This test controls the Type I experiment wise error rate. Alpha 0.05 Error Degrees of Freedom 16 Error Mean Square 8076.8 Critical Value of F 3.23887 Minimum Significant Difference 177.18 Means with the same letter are not significantly different. Scheffe’s Grouping Mean N Group A 243.20 5 s A A 192.00 5 sc A A 176.00 5 i A A 128.00 5 ic

The ANOVA analysis reveals that the F calculated p-value (0.2802) is greater than the

level of significance (0.05). In view of this, there is sufficient information in the data in

favour of the null hypothesis that the means of the treatment methods are the same. This

80

is also proven by the Post Hoc analysis of the data. Therefore, any method for water

treatment on COD (mg/l) may yield similar results.

3.8 Microbial load

Table 14: Microbiological characteristics of sewage effluent before and after

treatment

SAMPLE THB

CFU/ml

TC

CFU/100ml

FC

CFU/100ml

Raw sewage effluent 1210 348 162

Effluent after treatment using P.S 648 3 1

Effluent after using I.A 744 9 3

Effluent after treatment using SSF 767 0 0

P.S.: Pistia stratiotes, I.A: Ipomoea aquatica, CFU: coliform forming units, THB: Total

heterotrophic bacteria, TC: Total coliforms, FC: Faecal coliforms

Generally, there was a decrease in microbial load at the end of the experiment for both

plants as well as for the sand filter. After the tenth week of slow sand filtration, there was

zero count for total and faecal coliforms.

82

3.9 Comparison of efficiency of experimental sand filter to the filtration system of the Biogas plant

Table 15: Comparison of the quality of effluent for ten weeks of SSF to quality of effluent passing through the filtration system

of the VVU Biogas plant

WEEKLY VARIATION IN EFFLUENT QUALITY

Parameters analysed A 1 2 3 4 5 6 7 8 9 10 B

pH 4.13 6.54 6.515 7.585 7.165 6.87 6.785 6.685 6.6 6.725 7.105 6.98

Temperature (°C) 30.25 29.2 31.05 31.45 32.6 33.45 25.65 30.25 29.8 30 25.55 27.75

DO (mg/l) 1.935 6.1 5.1 4.25 3.7 3.65 3.55 4.6 5.6 5.7 5.75 4.19

BOD (mg/l) 35 25 21.5 11 8.5 7.5 5.5 4.3 2.35 1.25 1.05 26

COD (mg/l) 368 288 240 176 144 96 64 64 64 32 32 98

Turbidity (NTU) 159.5 119 12.5 10.95 9.75 9.7 11.25 7.95 7.1 6.6 5.8 47.5

Colour (PtCo) 731 565 234 217 210 206.5 199.5 199 198.5 196.5 184 515

TDS (mg/l) 2706.75 1877.5 1699 1429.5 1406.5 1374.25 1345.85 1271.5 1286.5 1274.5 1226.25 1704.8

EC (µs/cm) 5413.5 3755 3398 2859 2813 2748.5 2692 2579.5 2573 2549 2452.5 3409.5

Phosphates(mg/l) 5.47 3.55 3.03 2.81 3.35 3.97 3 2.895 2.84 2.705 2.54 3.02

Nitrates (mg/l) 2.65 1.7 8.45 9.4 10.7 8.2 5.65 4.3 4.25 4.3 3.4 5.75

TSS (mg/l) 238 221.5 21 18 14 11.5 10.5 6.5 7 5.5 5 65.5

A: Raw sewage effluent from intermediary chamber, B: effluent from the filtration system of the VVU Biogas facility

83

3.10 Quality assessment of safety of treated effluent for disposal/reuse

Table 16: Assessment of safety of effluent treated using SSF for disposal/reuse

Parameters analysed 1 2 3 4 5 6 7 8 9 10 GEPA (2004) WHO (1993)

p H 6.54 6.515 7.585 7.165 6.87 6.785 6.685 6.6 6.725 7.105 6-9 6.5-8.5

Temperature (°C) 29.2 31.05 31.45 32.6 33.45 25.65 30.25 29.8 30 25.55 < 3°C above

ambient

DO (mg/l) 6.1 5.1 4.25 3.7 3.65 3.55 4.6 5.6 5.7 5.75

BOD (mg/l) 25 21.5 11 8.5 7.5 5.5 4.3 2.35 1.25 1.05

COD (mg/l) 288 240 176 144 96 64 64 64 32 32

Turbidity (NTU) 119 12.5 10.95 9.75 9.7 11.25 7.95 7.1 6.6 5.8 75 5

Colour (PtCo) 565 234 217 210 206.5 199.5 199 198.5 196.5 184

TDS (mg/l) 1877.5 1699 1429.5 1406.5 1374.25 1345.85 1271.5 1286.5 1274.5 1226.25 1000

EC (µs/cm) 3755 3398 2859 2813 2748.5 2692 2579.5 2573 2549 2452.5 1500 700

Phosphates(mg/l) 3.55 3.03 2.81 3.35 3.97 3 2.895 2.84 2.705 2.54

Nitrates (mg/l) 1.7 8.45 9.4 10.7 8.2 5.65 4.3 4.25 4.3 3.4

TSS (mg/l) 221.5 21 18 14 11.5 10.5 6.5 7 5.5 5

Faecal coliforms

(CFU/100ml)

0 10 0

Total coliforms

(CFU/100ml)

0 400 0

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Table 17: Assessment of the quality of effluent treated using Pistia stratiotes for

disposal/use

Parameter Effluent treated

using

Pistia stratiotes

GEPA (2004)

(Max. permissible level)

for discharge into natural

waters

WHO (1993)

Max. value for drinking

water

p H 7.87 6-9 6.5-8.5

Temperature (°C) 25.1 <3°C above ambient -

DO (mg/l) 2.2 - -

BOD (mg/l) 17 - -

COD (mg/l) 224 - -

Phosphates (mg/l) 4.88 - -

Nitrates (mg/l) 1 - -

EC (µs/cm) 2975 1500 700

TDS (mg/l) 1488 1000 -

TSS (mg/l) 96 - -

Colour (PtCo) 530 - -

Turbidity (NTU) 90 75 5

Faecal coliforms

(cfu/100ml)

1 10 0

Total coliforms

(cfu/100ml)

3 400 0

Table 15 compares the experimental values to those obtained from the filtration system of

the Biogas plant. A is the raw effluent from the intermediary chamber of the Biogas

plant. A was subjected to slow sand filtration over a ten week period and the values

obtained on a weekly basis are shown. B is effluent obtained after the raw effluent went

85

through the filtration system of the biogas plant. From the table it is evident that there

were improvements in effluent quality for both the experimental filters and the filtration

system of the biogas plant.

It can be seen from table 16 that, the experimental sand filters reduced contaminants to

acceptable limits outlined by GEPA (2004) and WHO(1993) with the exception of TDS

and EC.

Table 17 above compares the quality effluent treated using Pistia stratiotes to standards

stipulated by GEPA (2004) and WHO (1993). Turbidity, EC and TDS did not meet the

standards.

86

Table 18: Assessment of the quality of effluent treated using Ipomoea aquatica for

disposal/ use

WEEK

Parameter 1 2 3 4 GEPA (2004)

WHO

(1993)

p H 7.38 7.22 7.77 7.65 6-9 6.5-8.5

Temperature (°C) 25.2 29.1 32 25.8 <3°C above

ambient

-

DO (mg/l) 2.1 3.5 1.9 4.1 - -

BOD (mg/l) 16 15.1 18 4.1 - -

COD (mg/l) 192 160 96 64 - -

Phosphates (mg/l) 4.7 3.9 5.64 8.24 - -

Nitrates (mg/l) 0 3.4 1.4 33.6 - -

EC (µs/cm) 3122 3105 3075 2030 1500 700

TDS (mg/l) 1901 1552.

5

1537.5 1015 1000 -

TSS (mg/l) 315 35 70 31 - -

Colour (PtCo) 718 664 533 334 - -

Turbidity (NTU) 147 20.2 54 12.9 75 5

Faecal coliforms (cfu/100ml) - - - 3 10 0

Total coliforms (cfu/100ml) - - - 9 400 0

87

3.11 Public perceptions on water scarcity and the reuse of wastewater

3.11.1 Demographic background of respondents

A total of 120 questionnaires were administered to students and staff of the Valley View

University. One hundred and two people completed the questionnaires, 46.1% male and

54% female. From the table, it can seen that higher proportions of the respondents were

between the ages of 18-30 (72.5%) and educated to the tertiary level. Majority (86.3%).

of the respondents are single.

Table 19: Demographic characteristics of respondents

Marital status Gender Age (Years) Educational level

Single Married Male Female 18-

30

31-

40

41-

60

Above

60

SHS Tertiary Others

Frequency 89 13 47 55 74 12 14 2 15 86 1

Percentage

(%)

87.3 12.7 46.1 53.9 72.5 11.8 13.7 2 14.7 84.3 1

3.11.2 Environmental perceptions

Fig 24 below shows that out of the 102 respondents interviewed, 57.8% have access to

treated tap water whilst 23.5% use water from the borehole. 2% have their source of

water from the stream whilst 6.9% harvest rain water for domestic use. 57.8% of

respondents stated that they have regular supply of water whiles the remaining 42.2% do

not have regular access.

88

Fig 24: Source of water for domestic use by respondents

89

3.11.3 Water as a scarce resource

Fig 25: Proportion of respondents who consider water to be a scarce resource

3.11.4 Causes of water scarcity

Fig 26: Causes of water scarcity stated by respondents

90

3.11.5 Sources of wastewater

Fig 27: Sources of wastewater stated by respondents

3.11.6 How wastewater is generated

Fig 28: How wastewater is generated by respondents

91

3.11.7 Use of wastewater generated at home

Fig 29: Uses of wastewater generated at home

All respondents admitted that they generate wastewater and the major source of

wastewater mentioned is domestic washing (81%). 13.7% generate wastewater through

work activities such as washing bay, tie and dye industry, catering industry and

commercial laundry.

Majority of the respondents (61.8%) mentioned that wastewater generated at home is

thrown away (Table 4.15). 36.3% use the wastewater for flushing toilet whilst 2% use the

wastewater for irrigation purposes. This result indicates that only 38.3% of the

92

respondents conserve water by reusing wastewater. From, Table 4.18 it is observed that

57.8% of respondents have regular access to water and this may explain why most of the

respondents throw the wastewater away.

3.11.8 Type of toilet facility

Fig 30: Type of toilet facilty respondents have access to

From the figure above, 88.2% of respondents have access to a toilet facility, the main

facility being water closet. However, only 47.1% have knowledge about how the human

excreta is disposed of as shown in the table below. This suggests that many people are

not conscious of their environment

93

3.11.9 Method of sewage disposal

Fig 31: Methods of disposal of sewage as stated by respondents

Out of the 48% of respondents who have an idea about the disposal of faecal matter,

26.5% mentioned dumping in the sea as the method of sewage disposal, while 17.65%

are aware of the use of sewage for production of biogas. A small proportion of the

respondents are aware of the use of sewage for compost (4.9) and irrigation of crops

(3.9%).

94

3.11.10 Reasons for supporting wastewater reuse

Fig 32: Respondents reasons for supporting wastewater reuse

Most of the respondents (31.4%) support wastewater reuse for the reason that it will

minimize dependency on treated water. 27.5% support use of wastewater for the reason

that it conserves water. 31.4% did not specify any reason and this may correspond to the

proportion of respondents (33.3%) who had no idea about wastewater reuse (Table 4.20).

this statistics suggests that a greater proportion of people are concerned about water

scarcity and water conservation.

95

42.2% of the respondents had no idea about health risks associated with wastewater

reuse. Among the health risks associated with wastewater reuse mentioned by

respondents are cholera (27.5%), bacterial infections (23.5%) and diarrhoea (5.9%). One

person mentioned candidiasis as the health risk associated with using wastewater

particularly for flushing toilets.

3.11.11 Health risks associated with wastewater reuse

Fig 33: Types of health risks associated with wastewater reuse as stated by

respondents

96

Fig 34: Respondents response on how health risks can be minimized

Whilst 62% of the respondents stated that treating the wastewater before use would

minimize the health risks, 11.8% prefer that the use of wastewater be avoided. This

suggests that more people agree that with treatment, wastewater can be used.

97

Most of the respondents (68.6%) are of the view that the Millennium Development Goal

(7) which highlights that the proportion of the population without sustainable access to

safe drinking water and basic sanitation be halved by the year 2015 cannot be achieved

3.11.12 Uses of wastewater

3.11.12.1 Irrigation of crops

Fig 35: Response of respondents to the use of treated wastewater for irrigation of

food crops

98

3.11.12.2 Fire fighting

Fig 36: Response of respondents to the use of treated wastewater for fire fighting

3.11.12.3 Industry

Fig 37: Response of respondents to the use of treated wastewater for industry

99

3.11.12.4 Construction of buildings

Fig 38: Response of respondents to the use of treated wastewater for construction of

buildings

3.11.12.5 Swimming pool

Fig 39: Response of respondents to the use of treated wastewater for swimming pool

100

3.11.12.6 Aquifer augmentation

Fig 40: Response of respondents to the use of trated wastewater for aquifer

augmentation

Of the reuse options suggested, most people supported to the use of treated wastewater

for irrigation (70.6%), firefighting (72.6%), industry (52.9%), construction of buildings

(72.6%), toilet flushing (82.4%), public park/ sports field irrigation (54.9%) and

commercial car wash (47.1%). This may be due to the belief that these options pose little

or no threat to human health. Only 29.4% of the respondents agreed to the use of the

treated water for aquifer augmentation and 53.9% were not sure. A higher percentage of

the respondents (47.1%) disagreed with the use of treated water for general cleaning and

101

laundry and swimming pool (65.7%) probably because there is high contact and health

risks may be high if the water is not properly treated.

Most of the respondents (52.9%) would not recommend wastewater use to their

communities and this means that more education is needed to encourage people to treat

and use wastewater.

102

CHAPTER FOUR

4.0 DISCUSSION

Results of the study showed that with the exception of nitrates, dissolved oxygen (DO)

and pH, all other parameters analyzed had higher values in the effluent from intermediary

point than in effluent from the final outlet. This suggests that the filtration system of the

biogas facility reduced contaminant load although the EC and TDS did not meet Ghana

EPA emission guidelines of 1500 µS/cm and 1000 mg/l respectively. The electrical

conductivity (EC), though reduced in the final effluent (3216-3603 µs/cm) far exceeds

the 1500 µS/cm set by GEPA (2010) maximum for disposal into the environment or for

use in agriculture. The EC of effluent discharged into the mango plantation is important

since the most influential water quality guideline on crop productivity is the water

salinity hazard as measured by electrical conductivity (Hamid et. al., 2013). The primary

effect of high EC water on crop productivity is the inability of the plant to compete with

ions in the soil solution for water, a condition known as Osmotic drought (physiological

drought). The higher the EC, the lesser is the water available to plants, even though the

soil may appear to be wet. Plants can only transpire "pure" water thus usable plant water

in the soil solution decreases dramatically as EC increases. The amount of water

transpired through a crop is directly related to yield. Therefore, irrigation water with high

EC reduces yield potential (Hamid et.al, 2013). Beyond effects on the immediate crop is

the long term impact of salt loading through the irrigation water.

Nitrates were also not efficiently removed as its concentration in the filtered effluent was

higher and this may be due to the conversion of ammonia nitrogen into nitrates through a

103

denitrification process. However, this poses no problem as plants utilize nitrates for

growth.

The faecal coliforms are within the 103 -106 CFU/100 ml set by WHO (2006) for use in

agriculture and aquaculture. The faecal coliforms are also within the WHO (2006) 1000

CFU/100ml limit for restricted irrigation and the 105/100ml for unrestricted irrigation.

The dissolved oxygen recorded a high value (2.98-5.4 mg/l) after filtration and this may

be due to a reduction in population of aerobic microorganisms. The pH of effluent from

the intermediary chamber was acidic (3.9-4.14). However, after passing through the

filtration system, the pH changed (6.47-7.48) and met the Ghana EPA recommended

limit i.e. 6-9. The COD of the final effluent was also within the 250mg/l GEPA (2010)

maximum permissible level for discharge into water bodies or for use in irrigation. The

BOD was also within the GEPA maximum acceptable standard of 50 mg/l for discharge

into water bodies and WHO (1989) standard of 20-100 mg/l for irrigation or aquaculture.

The heavy metals analysed were Zn, Pb, Fe, Cd, Cr, Cu and Ni. Apart from Fe and Cu,

all other heavy metals analysed were non detectable. In the digestion process,

putrefactive bacteria are present to degrade heavy metals during hydrolysis, acetogenesis

and methanogenesis (Issah and Salifu, 2012). From the results of this experiment, it can

be inferred that, Zn, Pb, Cd, Cr, and Ni if present, were probably degraded by

putrefactive bacteria but Cu and Fe could not be degraded by the putrefactive bacteria.

Notwithstanding this, the values recorded for Cu and Fe in the final effluent did not

104

exceed the WHO (1993) guideline maximum value for domestic use of water (2 mg/l for

Cu and 0.3 mg/l for Fe). The concentrations of Cu in the final effluent pose little threat to

the environment. This is because, when copper ends up in the soil, it strongly attaches to

organic matter and minerals. As a result, it does not travel far after release and it hardly

ever enters groundwater (Baysal et. al., 2013). Fe is not toxic to plants in aerated soils.

Contrary to a report by Foresti (2002) that effluents from anaerobic reactors treating

domestic sewage can rarely comply with the emission standards and that the main

important constituents or components deserving attention which are nutrients and

pathogens are not removed efficiently in the most commonly used anaerobic reactors, the

effluent from the VVU biogas, complies with guidelines for irrigation with the exception

of EC which exceeded the limit of 1500 µS/cm.

From the results of the phytoremediation experiment, it was observed that Pistia

stratiotes survived for only five days whilst Ipomoea aquatica survived for four weeks in

the raw sewage effluent. According to Piyush et. al. (2012), Pistia stratiotes is able to

survive in wastewater for a maximum period of 25 days. Haller et. al., (1974) reported

that Pistia Stratiotes has a higher survival rate at higher levels of electrical conductivity

(> 4000 µs/cm) but does not do well at higher COD levels. The electrical conductivity for

the raw sewage effluent used in this experiment was 5365 µS/cm which is tolerable but

the COD was 368mg/l, which may have been too high to support the growth of the plant

thus leading to the death of the plant after five days. When the raw effluent was diluted to

50% and 75%, the EC reduced to 2040 µs/cm and 1211µs/cm respectively but the COD

105

reduced to 354mg/l and 323mg/l respectively, Pistia stratiotes showed similar results, i.e.

died by the fifth day.

In the distilled water (control) which had lower EC (309 µS/cm) and COD of 256 mg/l,

Pistia stratiotes survived for two weeks even though the nitrate and phosphate

concentrations in the control were lower (0.5 mg/l and 1.7 mg/l respectively) than that in

the raw effluent (3.2 mg/l nitrates and 5.6 mg/l phosphates). This implies that Pistia

stratiotes can tolerate low nutrient levels.

Ipomoea aquatica plants developed new shoots and leaves after three days and survived

in the raw effluent for 28 days. In a study by Yu et. al. (2013) using Ipomoea aquatica to

purify biogas slurry, Ipomoea aquatica reached the highest peak of growth after 60 days.

This indicates that Ipomoea aquatica has high tolerance to contaminants and thus was

able to survive despite the high contaminant load.

The results showed that nitrogen and phosphorus were accumulated in both plants. Pistia

stratiotes accumulated less nitrogen (10.08%) and phosphorus (21.37%) than Ipomoea

aquatica (21.37%) which survived for four weeks. From the results of the experiment,

Ipomoea aquatica accumulated more nutrients at the end of the experiment than Pistia

stratiotes. This was expected since Ipomoea aquatica stayed longer in the sewage

effluent than Pistia stratiotes. Ipomoea aquatica shows much higher nutrient removal

efficiency with their high nutrient uptake capacity as shown in the figures 3 and 4 . It can

be seen that, after five days, there was a greater reduction in the concentration of

phosphates and nitrates when the raw effluent was treated with Ipomoea aquatica. Lu et.

al. (2013) reported that low concentrations of nutrients may reduce the performance of

106

plants in removing nutrients. This may be responsible for the low nutrient removal

efficiency of Pistia stratiotes.

After the first and second weeks of experiment, there was a reduction in BOD with a

corresponding increase in DO. This could be as a result of reduction in microbial activity

and photosynthesis. Photosynthesis results in greater dissolution of oxygen due to a

reduction in TDS. During the third week, a reduction in DO was observed corresponding

to a rise in BOD and this may be due to dead leaves falling back into the water and

decomposing leading to an increase in microbial activity. The microorganisms were using

up the DO in the water and that accounted for the decrease in DO. However, during the

fourth week, new shoots had sprouted and photosynthetic activity coupled with the

uptake of microorganisms by the plant led to an increase in the DO and a corresponding

decrease in the BOD.

Reduction of EC and TDS throughout the study period was due to absorption of dissolved

solids by Ipomoea aquatica.

Reduction in phosphates and nitrates is due to uptake by the plant as nutrients for growth.

The well-developed roots of aquatic plants have microbes attached to them and these help

to utilize nutrients (Wijetunga et.al, 2009). An increase in the phosphate concentration

after the second week may be due to falling leaves which decomposed and released the

phosphates back into the water.

All the nitrates were taken up after the first week of the experiment but increased again

after the second week. Some of the plants died when all the nitrogen was used up and

decomposition released the nitrates into the water which was used by the surviving plants

107

and new shoots developed. At the end of the experiment, there was an increase in

nitrogen concentration (33.6 mg/l).

The concentrations of nitrates and phosphates in the water were higher at the end of the

experiment and this suggests that most of the nutrients were released back into the water.

There was a progressive decrease in Chemical Oxygen Demand (COD) throughout the

experiment. The mean COD of the raw sewage effluent was 368 mg/l but this reduced to

64 mg/l by the end of the experiment corresponding to an 82.6% removal of COD. This

suggests that Ipomoea aquatica can assimilate COD. Decrease in COD may also be due

to an increasing DO thereby providing a better environment for oxidation. The microbes

around the roots of Ipomoea aquatica can also contribute to treatment by providing a

comfortable environment for the microbes thus removing organic matter effectively.

The filtration rate of the slow sand filter was high at the first run (733 ml/min) but

decreased with time of filter run. This is because as time went on, the sand grains settled

decreasing the voids which became clogged with particles from the raw sewage effluent.

Because of this, a drop in the filtration rate was observed. Around the fourth week, the

system started to level out with the filtration rate around 698 ml/min. At this point, the

sand was fully settled and saturated.

There was a notable positive reduction in the turbidity of the water samples after filtration

(even though turbidity was high). Turbidity decreases due to reduction in TDS and TSS.

These results agree with findings of El-Taweel (2000) that 92% of turbidity was removed

when slow sand filter was used for wastewater treatment. The major turbidity reduction

mechanism is believed to be through surface straining as predicted by Haarhoff and

108

Cleasby (1991). Excessive turbidity or cloudiness, in drinking water is aesthetically

unappealing and may also represent a health concern.

The concentration of nitrates reduced after the first run and shot up after the second week.

It reached a peak value after the fifth week and declined. An increase in concentration of

nitrates from the second week to the fifth week may be due to oxidation of ammonia

nitrogen to nitrates. After the fifth week, the growth of algae may have commenced

leading to the uptake of nitrates by the algae as nutrients for growth, thereby resulting in

a decrease in the concentration of nitrates.

A reduction in concentration of phosphates was observed until it increased from the fifth

to sixth week then a decline was observed. The reduction in phosphate concentration after

the sixth week may be due to uptake by algae growing on the surface of the filter bed.

Dissolved oxygen (DO) of raw sewage effluent was low before filtration (1.935 mg/l).

Low oxygen concentration is associated with heavy contamination by organic matter.

There was an increase in DO at the beginning of the experiment and this may be due to

the fact that the pores in the sand were filled with air and so there was a mixing of the

effluent with atmospheric oxygen. However, there was a decline after the second week

after which the concentration increased again after the 7th week. The decline was

probably due to the fact that the air pores were filled with raw effluent and microbial

activity was high. After the seventh week, enhancement of DO may be due to the

minimization of organic pollution load and microbial population due to their retention in

the filter bed and the simultaneous mixing with atmospheric oxygen.

109

Reduction in Biochemical Oxygen Demand (BOD) may be due to a reduction in the

bacterial population due to their retention on the surface of the filter bed as a result of the

formation of the dirt cover. Removal of BOD is related to the removal of TSS (Benth

et.al., 1981). A reduction in TSS was observed in this study.

The reduction in Chemical Oxygen Demand (COD) may be due to the fact that most of

the organic wastes were oxidized as they moved through the filter bed. A similar trend

was recorded by Rao et. al. (2003) when wastewater was filtered through slow sand filter.

Reduction in total suspended solids (TSS) is due to retention time of sewage effluent in

the filter bed. The sand filter primarily removes suspended solids and the effectiveness of

the filter is related to the removal of TSS (Benth et. al., 1981)

The main use of pH in water analysis is for detecting abnormal water (Tak et.al, 2012).

The initial pH of the sewage effluent used for this study was 4.04 which is acidic. The pH

of the water samples were taken (during the duration of the study) on a weekly basis.

There was an increase in pH both with the aquatic plants and with the sand filters. For

both technologies, pH ranged from 6.54 to 7.87. The increase in pH observed in effluent

treated with plants is basically attributed to the biochemical processes. Plants can absorb

anions such as NO3-, NO2

- and PO43- for their growth and, eventually resulting in the

reduction of acid forming anions leading to an increase in the pH.

Temperature is an important parameter because it affects chemical and biological

reactions and solubility of gases such as oxygen. Increasing temperature increases

reaction rates and solubility up to the point where temperature becomes high enough to

110

inhibit the activity of most microorganisms (around 35°C). During the study, the

temperature range was 25.1 - 33.45 which allows microbial activity.

An assessment of the microbial load of the effluent showed that, generally, there was a

decrease in microbial load at the end of the experiment for both plants as well as for the

sand filters. After the tenth week of filtration, there was zero count for total and faecal

coliforms. This is attributed to the fact that, the small sand grains provided a large total

surface area for biofilm growth. This biofilm, also known as dirt cover or

“schmutzdecke” layer may have resulted in the reduction in microbial load in the effluent

from the sand filter. This layer consists of the organic matter from the raw effluent that

settles on the filter surface and becomes a feeding ground for bacteria and

microorganisms. Thus, microorganisms spend longer time on the surface of the filter

resulting in a reduction in microbial load of effluent passing through the filter media.

Microbes in wastewater perform a vital role for the releasing of nutrient to the wastewater

by utilizing the organic compounds for their growth and development. Ipomoea aquatica

and Pistia stratiotes, which showed good performances with regard to pollutant removal,

had well developed root systems which facilitated the microbes to colonize well to form a

satisfactory habitat for their growth and development. A reduction in the microbial load

may be due to a migration of the microbes in the sewage effluent to the roots of the

aquatic plants used in this study. Eventually, the benefits of degradation product of

organic compounds are used by the aquatic macrophytes for their growth and

development. Therefore, it can be concluded that microbes as well as macrophytes, work

together to purify the polluted wastewater

111

A comparison of SSF and phytoremediation with Ipomoea aquatica using the one-way

ANOVA shows no significant difference in the turbidity and Chemical Oxygen Demand

(COD) of the treated effluent. This implies that if either of the two technologies is applied

in treating wastewater which is high in turbidity and COD, the same result would be

achieved.

There were significant differences in values obtained for dissolved oxygen (DO), nitrates

and phosphates. Based on these differences, SSF performed better at removing nitrates

and phosphates while Ipomoea aquatica proved better at replenishing DO. No significant

differences were recorded for electrical conductivity (EC), total dissolved solids (TDS),

total suspended solids (TSS), Biochemical Oxygen Demand (BOD) and colour. However,

when the mean values were compared, SSF was better at improving the quality of

effluent by reducing TSS, BOD and colour while Ipomoea aquatica was better at

reducing EC and TDS.

Phytoremediation using Pistia stratiotes produced an effluent which is higher in EC,

turbidity, total and faecal coliforms than the recommended values rendering the treated

effluent unsafe for domestic use and for disposal into natural water bodies. Electrical

conductivity of water is a useful and easy indicator of the salinity or total salt content of

water. Wastewater effluents often contain high amounts of dissolved salts from domestic

sewage. Build-up of salts from domestic wastes can interfere with water reuse by

municipalities, industries manufacturing textiles, paper and food products, and agriculture

for irrigation. High salt concentrations in waste effluents can increase the salinity of the

112

receiving water, which may result in adverse ecological effects on aquatic biota (Fried,

1991). Also, a very high salt concentration (> 1 000 mg/l) imparts a brackish, salty taste

to water and is discouraged because of the potential health hazard (WHO, 1979, Quality

of Domestic Water Supplies, 1998).

The effluent obtained from treatment with Pistia stratiotes had a turbidity value higher

(90 NTU) than the Ghana EPA recommended value for disposal into natural waters (75

NTU). An excessive value of turbidity is an indication of the presence of among other

things disease causing organisms and makes water purification processes difficult which

may increase treatment cost. High turbidity values are also an indication of

microbiological contamination (DWAF, 1998). This suggests that the effluent cannot be

consumed directly by human beings without treatment.

Dissolved Oxygen (DO) concentration in unpolluted water is normally about 8-10 mg/l at

25oC (DFID, 1999). Concentrations below 5.0 mg/l adversely affect aquatic life. The

treated effluent has a very low DO (2.2 mg/l) making it unsuitable for aquaculture.

For the protection of fisheries and aquatic life, the EU guidelines stipulate the BOD target

limits of 3.0-6.0 mg/l (Chapman, 1996). The high level in effluents treated with Pistia

stratiotes (17 mg/l) disqualifies the effluent for use as an aquatic ecosystem. The GEPA

(2010) proposes a BOD of 50-200 mg/l and 250-1000 mg/l COD for effluent discharge

into water bodies. This implies that considering BOD and COD, the effluent from

treatment with Pistia stratiotes can be safely discharged into water bodies.

113

The WHO safe limit for nitrate for lifetime use is 10 mg/l. Effluent treated with Pistia

stratiotes is within this limit and thus can be used for non-potable domestic purposes.

However, the effluents can be a source of eutrophication for the receiving water bodies as

the values obtained exceeded the recommended limits for no risk of 0-0.5 mg/l (DWAF,

1998).

The level of phosphate in water systems which will reduce the likelihood of algal and

other plant growth is 5µg/l (DWAF, 1998). This limit is exceeded by effluent treated with

Pistia stratiotes (4.88 mg/l). Based on this, treated effluent is not safe for disposal into

water bodies.

According to the WHO (1989) guidelines for coliform bacteria, a limit of 105 /100 ml is

recommended for unrestricted irrigation (i.e. irrigation of cereal crops, industrial crops,

fodder crops, pasture and trees) and 1000FC/100ml for restricted irrigation (irrigation of

crops likely to be eaten uncooked, sports field or public parks). The effluent from

treatment with Pistia stratiotes was well within the recommended limits and can be used

for irrigation.

In the current study, effluent obtained for each week of treatment was higher in EC,

turbidity, total and faecal coliforms than the recommended values. None of the effluents

obtained for any of the weeks is suitable for potable uses. Due to the high EC and TDS,

the effluent is unsuitable for discharge into natural water bodies and irrigation.

114

After the second week of treatment, Ipomoea aquatica reduced the turbidity to a value

lower (20.2 NTU) than the recommended value for discharge into natural waters (75

NTU). However, after the fourth week of treatment, the turbidity was still too high (12.9

NTU) for potable use (5 NTU). This implies that after two weeks of treatment of sewage

effluent with Ipomoea aquatica, the effluent can be discharged into natural waters.

For the protection of fisheries and aquatic life, the EU guidelines stipulate the BOD target

limits of 3.0-6.0 mg/l (Chapman, 1996). This is met by the effluent after the fourth week

of treatment (4.1mg/l). This means that, considering BOD, sewage effluent can be used

as an aquatic ecosystem only after the fourth week of treatment. The GEPA (2010)

proposes a BOD of 50-200 mg/l and 250-1000 mg/l COD for effluent discharge into

water bodies. This implies that considering BOD and COD, the effluent from treatment

with Ipomoea aquatica can be safely discharged into water bodies.

The effluent obtained from the first to third weeks of treatment meets the recommended

limit for nitrate for lifetime use (10 mg/l). After the fourth week, the limit was exceeded.

This means that effluents obtained from the first three weeks of treatment with Ipomoea

aquatica can be used for non-potable domestic purposes but effluent obtained after the

fourth week is not safe for lifetime use. The effluents can be a source of eutrophication

for the receiving water bodies as the values obtained exceeded the recommended limits

for no risk of 0-0.5 mg/l (DWAF, 1998). The level of phosphate in water systems which

will reduce the likelihood of algal and other plant growth is 5µg/l (DWAF, 1998). This

115

limit was exceeded by effluent treated with Ipomoea aquatica. The treated effluent is

therefore not safe for disposal into water bodies.

According to the WHO (1989) guidelines for coliform bacteria, a limit of 105 /100 ml is

recommended for unrestricted irrigation (i.e. irrigation of cereal crops, industrial crops,

fodder crops, pasture and trees) and 1000FC/100 ml for restricted irrigation (irrigation of

crops likely to be eaten uncooked, sports field or public parks). The faecal coliform count

of effluent obtained from treatment with Ipomoea aquatica is within the recommended

limits and can be used for irrigation.

In this study pH and temperature of all effluents were within the recommended limits for

domestic use, irrigation and discharge into natural waters.

Concentrations of DO below 5 mg/l adversely affect aquatic life. In this study, it was

observed that only the effluent from the first (6.1mg/l), second (5.1mg/l), eighth (5.6

mg/l), ninth (5.7mg/l) and tenth (5.75mg/l) weeks are suitable for discharge into an

aquatic environment. The EU guidelines for BOD for the protection of fisheries and

aquatic life i.e. 3.0-6.0 mg/l was met only by effluent obtained after the eighth

(2.35mg/l), ninth (1.25mg/l) and tenth (1.05 mg/l) weeks of SSF. The GEPA (2010)

proposes a BOD of 50-200 mg/l and 250-1000 mg/l COD for effluent discharge into

water bodies. The BOD for discharge into water bodies is met by all effluents.

Considering the COD limit for discharge into water bodies, only the effluents from the

second to tenth weeks of treatment meet the limit. The COD from effluent from the first

week of SSF exceeds the limit for discharge into water bodies.

116

Although SSF reduced EC and TDS progressively, the values obtained after the tenth

week were still too high and do not meet guidelines for irrigation, discharge into water

bodies and potable uses. The turbidity of effluent obtained from the second to tenth

weeks of SSF are within the Ghana EPA guideline for discharge into water bodies (75

NTU) but none of the effluents met the WHO guideline for drinking water (5 NTU). It is

possible that if the length of time for SSF is prolonged, the EC and turbidity would be

reduced to recommended limits.

The WHO safe limit for nitrate for lifetime use of 10 mg/l was met by effluent obtained

for all weeks of the SSF experiment with the exception of the fourth week which

recorded a value of 10.7 mg/l. The effluents obtained from all the weeks with the

exception of the fourth week can be used for domestic purposes such as toilet flushing,

laundry and cleaning of floors. However, the effluents can be a source of eutrophication

for the receiving water bodies as the values obtained exceeded the recommended limits

for no risk of 0-0.5 mg/l (DWAF, 1998). None of the effluents meet the 5 µg/l limit for

prevention of algal and other plant growth in water systems.

According to the WHO (1989) guidelines for coliform bacteria, a limit of105 /100 ml is

recommended for unrestricted irrigation (i.e. irrigation of cereal crops, industrial crops,

fodder crops, pasture and trees) and 1000FC/100ml for restricted irrigation (irrigation of

crops likely to be eaten uncooked, sports field or public parks). Effluent from the tenth

week of is well within the recommended limits and can be used for irrigation.

117

In this study, the performance of the experimental SSF was compared to that of the

filtration system of the Biogas plant. Both filtration systems changed the pH of the

effluent from acidic (4.13) to neutral. The experimental filters performed better at

replenishing the DO after the first four weeks and also after the seventh to tenth weeks.

During the fourth to sixth weeks, the filtration system of the Biogas facility performed

better.

The experimental sand filter was better at reducing the Biochemical Oxygen Demand

(BOD). After the first week of SSF the BOD was reduced to 25 mg/l which is lower than

that obtained for the filtration system of the Biogas facility (26 mg/l). EC and TDS values

were also lower after the second week of SSF than that obtained from the Biogas facility.

From the table, it can be seen that, after the tenth week, the SSF experiment was better at

enhancing DO, and reducing BOD, COD, turbidity, colour, TDS,TSS,EC, total and faecal

coliforms of the final effluent.

The results of the social survey show that the degree of close human contact is important

in determining public support of wastewater reuse. The results of this study seem to

parallel those of other studies by Bruvold (1984), EPA (1992), Crook et.al., (1994),

Freidler et al., (2006) and Hartley (2006), where high support was to low and medium

contact reuse options. In this study, medium contact options received high support. These

options are fire-fighting (71.6%), Industry (52.9%), construction of buildings (71.6%),

toilet flushing (81.4%), commercial car wash (46.1%) and public parks irrigation

(54.9%). There was low support for the high contact options such as swimming pool

118

(10.7%), aquifer augmentation (29.4%), and laundry (34.3%). Irrigation of food crops

which was considered to be a high contact option received high support (69.6%) probably

because it was perceived by the public as a medium contact option.

Most of the participants (65.7%) agreed that water is a scarce resource. Participants in the

survey who identified themselves as supporters of wastewater reuse revealed that the

most important reasons for their support minimization of dependency on treated water

(37.3%) and water conservation (36.3%) Environmental protection ranked as the third

most frequent response (26.5%). The demographic data shows that 83.3% of respondents

are educated to the tertiary level. However, only 48% are aware of how faecal matter is

disposed of. Of the disposal options, dumping into the sea and treatment to produce

biogas are well known among respondents. Very few know about the use of sewage for

irrigation and treatment to produce compost. Only 44.1% of the respondents are familiar

with the concept of wastewater reuse. These suggest that the level of environmental

awareness among the public is low.

Domenech and Sauri (2010) found out that the perception of health risks and

environmental awareness are in different degrees significant determinants of public

acceptance. According to these authors, improving the level of knowledge of health risks

and environmental awareness would reduce the risk of social refusal of wastewater

recycling.

The objectives of this study were achieved. The quality of sewage effluent from the VVU

Biogas facility was monitored. Slow sand filtration and Phytoremediation technologies

were successful at treating the raw effluent to some extent.

119

CHAPTER FIVE

5.0 CONCLUSIONS

The results of this study substantiate that phytoremediation and Slow Sand Filtration are

effective methods for the treatment of wastewater. Phytoremediation and Slow Sand

Filtration (SSF) are effective methods for treating sewage effluent. Generally, both

technologies reduce contaminant levels. However, phytoremediation with Ipomoea

aquatica is better than sand filtration at reducing EC and TDS. Sand filtration performed

better at enhancing DO whilst reducing colour, nitrates, phosphates and BOD. Both

technologies are equally effective at reducing turbidity, TSS, and COD since there was

no significant difference in mean values obtained for these parameters. Both technologies

changed the p H from acidic to neutral.

Pistia stratiotes and Ipomoea aquatica are both effective at reducing contaminant load.

However, the results of this study show that Pistia stratiotes does not survive for long in

sewage effluent. Dilution of effluent gave similar results.

Most of the parameters analysed with respect to the sewage effluent from the Valley

View University Biogas facility fell within the acceptable guidelines with the exception

of EC.

Treated effluents were of different qualities and are applicable, depending on the quality,

for use in irrigation, aquaculture and non-potable domestic uses as well as safe for

disposal into water bodies. The effluents are however not safe for potable uses.

120

Majority of respondents agree that water is a scarce resource and that the Millennium

Development Goal (MDG) on water cannot be achieved. Majority of people interviewed

support the use of wastewater for medium contact options such as fire- fighting (71.6%),

Industry (52.9%), construction of buildings (71.6%), toilet flushing (81.4%), Public parks

and sports field irrigation (54.9%). Support for high contact options such as swimming

pool, aquifer augmentation and laundry was low; 10.7%, 29.4% and 34.3% respectively

and this is because respondents consider the treated water to be detrimental to health.

Respondents supported the idea of wastewater reuse for reasons of water conservation

and minimization of dependency on treated water whilst environmental protection ranked

as the least frequent response. Education is needed to sensitize the public on treatment

and use of wastewater.

RECOMMENDATIONS

1. It is recommended that a strategy be put in place to reduce the electrical

conductivity of the effluent discharged from the VVU Biogas facility into the

mango plantation. Salt loading of the irrigated soil should be monitored

periodically due to the high EC of discharged effluent

2. Plant biomass of plants used for the phytoremediation experiment should be

reduced by methods such as anaerobic digestion, drying and disposed at a

landfill site

3. More work should be done on phytoremediation of sewage effluent using Pistia

stratiotes.

121

(B) The length of Slow Sand Filtration (SSF) experiment, if prolonged, may produce

an effluent which may be safe for potable uses. Further work should be done on

SSF using sand from different sources. The schmuzdecke layer formed on top of

the sand should be disposed at a landfill site due to the high levels of

contaminants. The SSF should also be monitored to prevent the presence of

insects and other animals.

122

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APPENDICES

Appendix one: Filtration rate through slow sand filter column

WEEK RAW SEWAGE

EFFLUENT (ml/min)

CONTROL(ml/min)

0 733 733

1 730 732

2 729 730

3 704 726

4 698 719

5 605.5 719

6 564 711

7 553 708

8 448 705

9 431 703

10 416 701

134

Appendix two: Performance of slow sand filtration (SSF)

WEEK PH TEMP (°C) TURBIDITY (NTU) EC (µs/CM) TDS (mg/l)

MEAN CO NTRO LMEAN CO NTRO LMEAN CO NTRO L MEAN CO NTRO LMEAN CO NTRO L

0 4.13 7.32 30.25 27 159.5 0.8 5413.5 347 2706.75 173.5

1 6.54 6.91 29.2 33.5 119 1.1 3755 345 1877.5 172.5

2 6.515 6.63 31.05 25.6 12.5 1 3398 326 1699 163

3 7.585 6.8 31.45 29.9 10.95 1 2859 355 1429.5 177.5

4 7.165 7.1 32.6 29.6 9.75 1 2813 352 1406.5 176

5 6.87 6.68 33.45 31.6 9.7 0.9 2748.5 345 1374.25 172.5

6 6.785 6.82 25.65 25.6 11.25 0.7 2692 339 1345.85 169.5

7 6.685 6.5 30.25 30.2 7.95 0.6 2579.5 334 1271.5 167

8 6.6 6.92 29.8 30.2 7.1 0.7 2573 323 1286.5 161.5

9 6.725 7.01 30 29.6 6.6 0.6 2549 318 1274.5 159

10 7.105 7.23 25.55 27.2 5.8 0.6 2452.5 312 1226.25 156

WEEK TSS (mg/l) CO LO R (PtCo) NO 3(mg/l) PO 4 (mg/l) DO (mg/l) BO D (mg/l) CO D (mg/l)

CO NTRO L MEAN CO NTRO LMEAN CO NTRO L MEAN CO NTRO LMEAN CO NTRO LMEAN CO NTRO LMEAN CO NTRO L MEAN CO NTRO L

0 238 8 731 7 2.65 3.5 5.47 1.44 1.935 6 35 6.2 368 256

1 221.5 6 565 5 1.7 1.3 3.55 1.14 6.1 5.5 25 4.5 288 224

2 21 6 234 4 8.45 1 3.03 1.09 5.1 4.6 21.5 0.9 240 192

3 18 6 217 4 9.4 1.3 2.81 2.49 4.25 5.3 11 0.2 176 160

4 14 5 210 4 10.7 1.5 3.35 2.54 3.7 4.5 8.5 0.2 144 128

5 11.5 4 206.5 3 8.2 1.4 3.97 2.56 3.65 5.1 7.5 0.1 96 96

6 10.5 4 199.5 0 5.65 1.2 3 1.96 3.55 6.5 5.5 0.1 64 64

7 6.5 4 199 0 4.3 0.8 2.895 1.86 4.6 6.6 4.3 0.1 64 32

8 7 4 198.5 0 4.25 0.8 2.84 1.82 5.6 6.5 2.35 0.1 64 32

9 5.5 4 196.5 1 4.3 0.6 2.705 1.76 5.7 6.3 1.25 0 32 32

10 5 3 184 0 3.4 0.6 2.54 1.62 5.75 5.9 1.05 0.1 32 32

Appendix three: Quality of effluent after treatment with Ipomoea aquatica and Pistia

stratiotes for five days

PH TEMP (°C) DO (mg/l) EC (µS/cm) TDS (mg/l)

MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL

RAW EFFLUENT 4.04 7.72 30.5 33.6 0.17 6.3 5365 309 2682.5 154.5

P.S treated effluent 7.87 6.76 25.1 29.9 2.2 3.1 2975 295 1488 147.5

I.A treated effluent 7.38 6.45 25.2 25.1 2.1 4.3 3122 287 1901 143.5

TSS (mg/l) COLOUR (PtCo) TURBIDITY (NTU) PO4 (mg/l) NO3 (mg/l) BOD (mg/l) COD (mg/l)

MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL

RAW EFFLUENT 239 6 738 21 143 4 5.6 1.7 3.2 0.5 35 6.2 368 256

P.S treated effluent 96 16 530 190 90 2.99 4.88 0.95 1 0.2 17 1.8 224 96

I.A treated effluent 315 23 718 201 147 2.18 4.7 0.2 0 0.2 16 3 192 96

135

Appendix Four: Weekly variations in water quality parameters after during treatment

with Ipomoea aquatica

PH TEMP (°C) DO (mg/l) EC (mg/l) TDS (mg/l)

WEEK MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL

0 4.14 7.72 30.5 33.6 0.17 6.3 5365 309 2683 154.5

1 7.38 6.45 25.2 25.1 2.1 4.3 3122 287 1901 143.5

2 7.22 6.06 29.1 29 3.5 4.8 3105 276 1552.5 138

3 7.77 6.75 32 32.2 1.9 5.5 3075 255 1537.5 127.5

4 7.65 7.19 25.8 22.7 4.1 6.7 2030 231 1015 115.5

TSS (mg/l) COLOUR (PtCo) TURBIDITY(NTU) (NTU) PO4 (mg/l) NO3 (mg/l) BOD (mg/l) COD (mg/l)

WEEK MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL MEAN CONTROL

0 239 6 738 21 143 4 5.6 1.7 3.2 0.5 35 6.2 368 256

1 315 23 718 20.1 147 2.18 4.7 0.2 0 0.2 16 4.3 192 160

2 35 10 664 19 20.2 5.4 3.9 0.1 3.4 0 15.1 3.2 160 128

3 70 3 533 15.2 54 1.8 5.64 1.2 1.4 0.8 18 1.8 96 64

4 31 15 334 10.4 12.9 6.3 8.24 7.04 33.6 0.3 4.1 0.9 64 32

136

Appendix Five: Questionnaire

UNIVERSITY OF GHANA

INSTITUTE FOR ENVIRONMENT AND SANITATION STUDIES (IESS)

QUESTIONNAIRE

One of the pressing environmental problems in the world today is water scarcity. It is

increasingly becoming important to seek alternative sources of water to supplement the

available water. One attractive option is wastewater treatment and reuse. This

questionnaire is designed to get your views on reuse of wastewater.

This questionnaire is solely for academic purposes and confidentiality is assured.

Please answer the following questions regarding the treatment and reuse of

wastewater.

(A) Demographic background (Please tick)

Gender M Age 18-30

F 31-40

41-50

51-60

Above 60

Highest level of education

(a)Primary

(b)JHS

© SHS

(d)Tertiary

(e)Other (Please specify)

Marital status single

Married

Widowed

Number of children……………………………………………………………

Place of residence……………………………………………………………

137

Monthly Income (GH¢) (Please tick)

Below 100

100-300

500-1000

Above 1000

(B) Environmental perceptions

1. How do you get water for domestic use? (Please tick as many options as

possible)

(a)Treated tap water

(b)Borehole

© River/stream

(d)Rain water harvesting

(e) Other (please specify)………………………………..

2. Do you have regular access to water? Yes/ No

3. If yes, how regular is your supply of water?

(a) Daily

(b) Once a week

(c) Once a month

(d) Other (please specify)……………………………………….

4. Do you consider water to be a scarce resource? Yes/No

5. What are some of the causes of water scarcity you know about? (Please tick

as many options as applicable)

(a) Water pollution

(b) Drought

(c) Depletion of aquifers

(d) Others (please

specify)……………………………………………………………………

………………………………………………………………………………

………………

6. What do you understand by the term “wastewater”?

(a) Any dirty and unclean water

(b) Water which has already been used

138

(c) Water which cannot be used any longer

(d) Others (please

specify)……………………………………………………………………

………………………………………………………………………………

…………….

7. What are some of the sources of wastewater you know about? (Please tick as

many options as applicable)

(a) Domestic washing

(b) Sewage

© Washing bay

(e) Industries

(f) Rainfall run off

(g) Others (please specify)

………………………………………………………………………………

………………………………………………………………………………

………………

8. Do you generate wastewater? Yes/No

9. If Yes, how do you generate wastewater?

(a) Domestic washing

(b) Work activities

(c) Others (please

specify)……………………………………………………………………

………………………………………………………………………………

………………

10. What do you do with wastewater generated at home? (Please tick as many

options as applicable)

(a) Throw it away

(b) Flushing toilet

(c) Irrigation

(d) Others (please

specify)……………………………………………………………………

………..

139

11. Do you have access to a toilet facility? Yes/No

If yes, indicate (by ticking) which toilet facility you have access to.

(a) Water closet

(b) KVIP

(c) Pit latrine

(d) Open defecation

12. Do you have any idea about how the faecalmatter generated by humans is

disposed off? Yes/ No

13. If yes, please indicate (by ticking), the methods of disposal you know about

(a) Dumping into the sea

(b) Irrigation of crops

(c) Treatment to produce compost

(d) Treatment to produce Biogas

(e) Others (please

specify)…………………………………………………………………………

…………………………………………………………………………………

…………………………………………………………………………………

……………………….

14. Are you familiar with the concept of wastewater reuse? Yes /No

15. Do you support the idea of wastewater reuse? Yes/No

16. If yes, what are your reasons for supporting wastewater reuse? (Please tickas

many options as applicable)

a. Wastewater reuse is good for the environment

b. Wastewater reuse conserves water

c. Wastewater reuse will minimize dependency on treated water

17. Do you know of any health risks associated with wastewater reuse? Yes/No

18. If yes, please indicate (by ticking) the health risks you know about

(a) Cholera

(b) Bacterial infections

(c) Diarrhoea

(d) Others (please

specify)……………………………………………………………………

………………………………………………………………………………

…………….

19. Do you know how the health risks mentioned above can be minimized or

prevented? Yes/No

(a) By treating water before use

140

(b) Avoiding the use of wastewater

(c) Others (please

specify)………………………………………………………………………………

………………………………………………………………………………………

……………….

20. The Millenium Development Goal 7 targets that the proportion of the

population without sustainable access to safe drinking water and basic

sanitation be halved by the year 2015. Can this be achieved? Yes/No

21. Please indicate ( by ticking) whether you support the following options for

wastewater reuse

Wastewater

reuse option

Strongly

agree

Agree Not

sure

disagree Strongly

disagree

Irrigation of

food crops

Fire fighting

Industry

Construction of

buildings

Toilet flushing

Public

park/sports field

irrigation

Commercial car

wash

Swimming pool

Aquifer

augmentation

General

cleaning and

laundry

22. Would you recommend wastewater use to your community? Yes/No