Wastewater Treatment

Al-Azhar University-Gaza

Master Program of Water and Environmental Science

OutlineDefinitions:

Characteristics of wastewaters:

The global extent

Economic benefits and risks of Wastewater treatmentEconomic Benefits Economic risksSocial and health benefits and risks Environmental benefits and risks 

Conventional wastewater treatment processes:Preliminary treatmentPrimary treatmentSecondary treatmentTertiary and/or advanced treatmentDisinfection 

OutlineWaste water treatment in the Gaza Strip

Wastewater Treatment Plants in the Gaza StripBeit Lahiya Treatment Plant Sheikh Ajleen Treatment PlantRafah Treatment PlantKhanyounis Temporary Treatment Plant

Nitrate pollution of ground water in Gaza Strip aquifer

References

Definition:Waste water:

Sewage water is known as the quantities of water used by the human population, whether for domestic or industrial purposes. It contains both dissolved and solid contaminants. It is generally collected in sewers that all together compose the sewage system.

Definition:Wastewater: Urban wastewater is usually a combination of one or more of the following which makes it polluted water:Domestic effluent consisting of blackwater (excreta, urine and faecal sludge, i.e. toilet wastewater) and grey-water (kitchen and bathing wastewater)Water from commercial establishments and institutions, including hospitalsIndustrial effluent where presentStorm-water and other urban run-off.

Treated wastewater: Is wastewater that has been processed through a wastewater treatment plant up to certain standards in order to reduce its pollution or health hazard; if this is not fulfilled; the wastewater is considered at best as partially treated.

Reclaimed wastewater: or recycled water is treated wastewater that can officially be used under controlled conditions for beneficial purposes such as irrigation

Characteristics of wastewaters:Municipal wastewater is mainly comprised of water (99.9%) together with relatively small concentrations of suspended and dissolved organic (carbohydrates, lignin, fats, soaps, synthetic detergents, proteins…) and inorganic solids

Wastewater = clean water supply + solids

Table1:Majour constituents of typical domestic wastewater

ConstituentConcentration, mg/lStrongMediumWeak

Total solids1200700350Dissolved solids (TDS)1850500250Suspended solids350200100Nitrogen (as N)854020Phosphorus (as P)20106Chloride11005030Alkalinity (as CaCO3)20010050Grease15010050BOD5

2300200100

In arid and semi-arid countries, water use is often fairly low and sewage tends to be very strong

Table 2: Average composition of wastewater in Amman, Jordan

ConstituentConcentration mg/lDissolved solids (TDS)1170Suspended solids900Nitrogen (as N)150Phosphorus (as P)25Alkalinity (as CaCO3)850Sulphate (as SO4)90BOD5770COD11830TOC1220

Table 3: Chemical composition of wastewater in Alexandria and Giza , Egypt

ConstituentAlexandriaGizaUnitConcentrationUnitConcentration

ECdS/m3.10dS/m1.7pH7.807.1

SAR9.302.8Na2

+me/l24.60mg/l205Ca2

+me/I1.50mg/l128Mgme/I3.20mg/l96K+me/I1.80mg/l35Cl-me/I62.00mg/l320

SO42-me/I35.00mg/l138

CO3me/I1.10HCO3

-me/I6.60NH4

+mg/l2.50NO3mg/l10.10

Pmg/l8.50Mnmg/l0.20mg/l0.7Cumg/l1.10mg/l0.4Znmg/l0.80mg/l1.4

Table 4: Possible levels of pathogens in wastewater

Type of pathogen Possible concentration per litre in municipal

wastewater1 Viruses: Enteroviruses 5000 Bacteria: Pathogenic E. coli?

Salmonella spp. 7000 Shigella spp. 7000 Vibrio cholerae `1000

Protozoa: Entamoeba histolytica 4500 Helminths:  

Ascaris Lumbricoides 600 Hookworms4 32 Schistosoma mansoni 1 Taenia saginata 10 Trichuris trichiura 120

The global extent Earth contains an estimated 1351 million cubic km of water, Only 0.003 % of this is classified as fresh water.

The common needs for water fall into the following categories:Drinking waterAgriculturePersonal hygiene and public sanitationDomestic uses (food preparation, cleaning, outdoor uses)

The common needs for water Commerce and services Industry Recreation and tourism Environmental and ecological maintenance,

conservation and protection

Table 5: Threshold values used to characterize water stress within a region

Characteristic Threshold SituationWater Scarcity Index, m3/ capita /yr

Water stress<1 700The region begins to experience water stress and the economy or human health may be harmed

Chronic water scarcity

<1 000The region experiences frequent water supply problems, both shortand long-term

Absolute water stress

<500The region completes its water supply by desalting seawater, overexploiting aquifers or performing unplanned water reuse

Minimum survival level

<100Water supply for domestic and commercial uses is compromised, since the total availability is not enough to fulfil demand for all uses (municipal, agricultural and industrial)

Economic benefits and risks of Wastewater treatment

Economic Benefits:Serve as a more dependable water source. Enhance urban, rural and coastal landscapes, thereby increasing employment and local economy through tourismBe substituted for freshwater or potable water to meet specific needs and purposes (such as irrigation, toilet flushing, cooling...)Reduction or elimination of fertilizer application.In many applications, treated wastewater reuse is less costly than using freshwater, pumping deep groundwater, importing water, building dams or seawater desalination

Economic risks The economic impact of public health epidemics or

environmental pollution High distribution and storage costs due to the distance between

supply and demand location Weak economic justification when water prices do not cover the

true cost. The local market demand for treated wastewater is not clearly

defined and agreed Negative branding of treated wastewater reuse by the general

public.

Social and health benefits and risks

Social and health benefitsHelping to achieve Millennium Development Goals (MDG) through increasing water availability and poverty reductionContributes to food security, better nutrition and sustains agricultural employment for many householdsIncreased quality of life, well being and health through attractive irrigated landscapes in parks and sports facilities in rich and poor communities

Social and health risks Threat to public health, especially if illegal and unhealthy

wastewater reuse practice expands due to water scarcity.

Social tensions in case of non-acceptance:

Environmental benefits Treated wastewater reuse allows for the conservation and

rational allocation of freshwater resources, particularly in areas under water stress.

Reduces the amount of discharges and therefore the level of nutrients or other pollutants entering waterways

Provides a mitigation solution to climate change through the reduction in green house gas by using less energy for wastewater management rather than importing water, pumping deep groundwater, seawater desalination or exporting wastewater

Reduces the need for chemical fertilizers Sludge can be used as soil conditioners Treated wastewater can be used to recharge aquifers.

Environmental risks Hazardous or toxic waste and salts from industry can reduce

the quality of the wastewater and risk public health

Reused treated wastewater may constitute an additional pressure onto the aquatic environment

Conventional wastewater treatment processes

Conventional wastewater treatment consists of a combination of physical, chemical, and biological processes and operations to remove solids, organic matter and, sometimes, nutrients from wastewater

General terms used to describe different degrees of wastewater treatment are, preliminary, primary, secondary, and tertiary and/or advanced wastewater treatment

Preliminary treatmentPreliminary treatment:

screening and grit removal to remove coarse solid and other large materials often found in raw wastewater. It includes coarse screening and grit removal.

Primary treatment:Primary treatment: sedimentation – simple settlement of solid material in a primary settling tank. Solid particles settle at the bottom, and oils and greases rise to the top. This material is removed as sludge, for separate treatment.Approximately 25-50% of the incoming BOD5, 50-70% of the total suspended solids (SS), and 65% of the oil and grease are removed during primary treatmentSome organic nitrogen, organic phosphorus, and heavy metals associated with solids are also removed during primary sedimentation but colloidal and dissolved constituents are not removed.

Table 6: Quality for raw wastewater and primary effluent at selected treatment plants in California

Quality parameters (mg/l, except as otherwise

indicated)

City of Davis San Diego Los Angeles County Joint Plant Raw

wastewater Primary effluent

Raw wastewater

Primary effluent

Raw wastewater

Primary effluent

BOD5 112 73 184 134 - 204

Total organic carbon 63.8 40.6 64.8 52.3 - -

Suspended solids 185 72 200 109 - 219 Total nitrogen 43.4 34.7 - - - - NH3-N 35.6 26.2 21.0 20.0 - 39.5 NO-N 0 0 - - - - Org-N 7.8 8.5 - - - 14.9 Total phosphorus - 7.5 - 10.2 - 11.2

Ortho-P - 7.5 11.2 -

pH (unit) 7.7 - 7.3 7.3 - - Cations:

Ca - - - - 78.8 - Mg - - - - 25.6 - Na - - - - 357 359 K - - - - 19 19

Anions: SO4 - 160 270

Cl - 120 397

Electrical conductivity, dS/m 2.52 2.34 2.19 -

Total dissolved solids - - 829 821 1404 1406

Soluble sodium percentage, % - - 70.3

Sodium adsorption ratio - - - - 8.85 6.8

Boron (B) - - - - 1.68 1.5 Alkalinity (CaCO3) - - - 322 332

Hardness (CaCO3) - - 265

Secondary treatment Wastewater from primary treatment flows into an aeration tank,

to which micro-organisms are added to consume the remaining organic matter.

Following aeration, the mixture is clarified. The residue is removed as sludge, for separate treatment and disposal.

Several aerobic biological processes are used for secondary treatment differing primarily in the manner in which oxygen is supplied to the microorganisms and in the rate at which organisms metabolize the organic matter.

High-rate biological treatment processes, in combination with primary sedimentation, typically remove 85 % of the BOD5 and SS originally present in the raw wastewater and some of the heavy metals.

Activated Sludge

Trickling Filters

Rotating Biological Contactors

Table7: Quality of secondary effluent at selected wastewater treatment plant in California

Quality parameter (mg/I except as otherwise

indicated)

Plant location Trickling filters Activated sludge

Chino Basin MWD (No. 1)

Chino Basin MWD (No. 2)

Santa Rosa Laguna Montecito Sanitary District

BOD5 21 8 - 11

COD- - 27 -

Suspended solids 18 26 - 13 Total nitrogen - - - - NH3-N 25 11 10 1.4 NO3-N 0.7 19 8 5 Org-N - - 1.7 - Total phosphorus - - 12.5 - Ortho-P - - 3.4 - pH (unit) - - - 7.6

Cations: Ca 43 55 41 82 Mg 12 18 18 33 Na 83 102 94 - K 17 20 11 -

Anions: HCO3 293 192 165 - SO4 85 143 66 192 Cl 81 90 121 245 Electrical conductivity dS/m - - - 1.39

Total dissolved solids 476 591 484 940 Sodium adsorption ratio 2.9 3.1 3.9 3.7

Boron (B) 0.7 0.6 0.6 0.7 Alkalinity (CaCO3) - - - 226 Total Hardness (CaCO3) 156 200 175

Tertiary and/or advanced treatment

It is employed when specific wastewater constituents which cannot be removed by secondary treatment must be removed

Individual treatment processes are necessary to remove nitrogen, phosphorus, additional suspended solids, refractory organics, heavy metals and dissolved solids

Advanced treatment processes are sometimes combined with primary or secondary treatment

Disinfection Involves using of chlorine solution injection, ozone and

ultra violet (UV) Chlorine solution is the most common disinfectant used in

wastewater treatment The bactericidal effects of chlorine depends on pH, contact

time, organic content, and effluent temperature. Dosages of 5-15 mg/l are common, with contact time of 30

minutes To meet advanced wastewater treatment requirements, a

chlorine contact time of as long as 120 minutes is sometimes required for specific irrigation uses of reclaimed wastewater

Waste water treatment in Gaza StripTable 8: waste water networks coverage in Gaza strip governorates

GovernorateCovering %

North % 80

Gaza % 90

Middle Area% 70

Khanyouness% 40

Rafah% 70

The overall ratio wastewater coverage

% 70.7

Middle area There is currently no wastewater treatment plant in this

Governorate.

Most raw sewage is collected in a concrete pipe through Salah Aldeen Road and slopes to Wadi Gaza, and then flows to the sea.

The flow rate of untreated sewage into the sea is about 10,000 m3/day.

Wastewater Treatment Plants in the Gaza Strip

The quantity of wastewater produced in Gaza strip is more than 30 million cubic meter per year. The BOD5 level is about 600 mg/l, which means that the wastewater in Gaza Strip is strong, and that due to the low portion of fresh water for citizens (70-90 liters per capita / day).

In the Gaza Strip, there are three main treatment plants and one temporary plant for collecting and treating wastewater

The current treatment plants still do not meet the standards of treating wastewater in Gaza

Beit Lahiya wastewater treatment plant

Beit Lahiya treatment plant was established in 1974 by the Israeli Civil Administration in the town of Beit Lahiya in the northern area of the Gaza Strip

The aim behind the plant establishment was to re-use the treated wastewater for agricultural purposes but this aim was not achieved

Current inflows to the plant are greater than 17,000 m3/day, beyond plant capacity

The partially treated wastewater is pumped to the northern and eastern infiltration lagoons in the same governorate.

Sheikh Ajleen Treatment Plant The plant was established in 1979 with an infiltration basin next

to it In 1986 the (UNDP) established another two infiltration basin to

develop the plant. In1996 the Municipality of Gaza and UNRWA developed it in

order to recharge 12,000 cubic meters per day. In 1998 the plant was rehabilitated and its capacity was enlarged

to recharge 35,000 cubic meters per day. In 2009 the water pumped to the plant increased to 60,000 cubic

meters per day and this exceeds the plant capacity After the year 2005 many people seized the plant infiltration

basins and turned them into agricultural lands, thus the semi-treated WW was pumped to the sea

Rafah Treatment Plant Rafah treatment plant was established in 1989 near in Tel Al-

Sultan in the western of Rafah It consists of a lagoon with four aerators The capacity of the treatment plant is 4,000 cubic meters only per

day. the current flow is up to 8,500 m3/day The treatment of the plant is inadequate (effluent characteristics

are BOD 300ppm, COD 550ppm, and TSS 250ppm) virtually untreated sewage is being discharged to the sea

Khanyounis Temporary Treatment Plant In late 2007, CMWU gradually established wastewater lagoons

in Almawassi area where the last one was established in early 2009

Those lagoons were established to pump the water from Hai El-Amal lagoons

Hai El-Amal lagoons were established in year 2003 to collect and infiltrate storm water of khanyounis, but due to the frequent closure and the Israeli harassments during the establishment of project the project was suspended

deteriorated infrastructure changed the lagoons into an outlet for the wastewater pumped from the whole district

The current flow rate is about 5,000 m3/day

Nitrate pollution of ground water in the Gaza Strip aquifer

The groundwater aquifer of Gaza is extremely susceptible to surface-derived contamination because of the high permeability of sands and gravels that compose the soil profile of Gaza.

Almost 90% of the groundwater wells of the Gaza Strip sampled between 2001 and 2007 showed NO3 – concentrations two to eight times higher than the WHO standards.

NO3 − in the groundwater of the Gaza Strip occurred as a result of NO3 − leaching from irrigation, wastewater septic tanks, sewage sludge, animal manure and synthetic fertilizers.

Nitrate pollution of ground water

Recent observations revealed a high positive correlation between the concentrations of NO3 − (N80 mg/l) in groundwater of the Gaza Strip and the occurrence of methemoglobinemia in babies younger than six months of age

Among 640 babies tested in Gaza, 50% showed signs of methemoglobinemia in their blood samples.

References1. Abdel Fattah N. Abd Rabou .2011. Environmental Impacts Associated with

the Beit Lahia Wastewater Treatment Plant, North Gaza Strip, Palestine: Middle-East Journal of Scientific Research 7 (5): 746-757, 2011. ISSN 1990-9233

2. B. H. Shomar, G. Muller, and A. Yahya, “Potential use of treated wastewater and sludge in the agricultural sector of the Gaza Strip”, Clean Techn Environ Policy, Vol. 6, 2004.

3. Baalousha H (2008) Analysis of nitrate occurrence and distribution in groundwater in the Gaza Strip using major ion chemistry. Global NEST J 10:337–349

4. Basem Shomara, Karsten Osenbrückb and Alfred Yahyaa. (2008). Elevated nitrate levels in the groundwater of the Gaza Strip: Distribution and sources. SCIENCE OF THE TOTAL ENVIRONMENT 398 164–174.

5. CMWU, 2010,Annual Report on Water Status in the Gaza Strip,

References6. FAO (1992) Wastewater treatment and use in agriculture - FAO irrigation

and drainage paper 47. FAO, Rome.

7. Fareed Ashour1, Bashar Ashour2, Marek Komarzynski3, Yasser Nassar4, Mary Kudla5, Najla Shawa6 and Graham Henderson6 , 2009, A brief outline of the sewage infrastructure and public health risks in the Gaza Strip for the World Health Organisation.

8. The Economics of Wastewater Use in Agriculture. In: FAO Water Reports, 35/ FAO, James Winpenny, et,al. (2010). Rome, Italy, Electronic Publishing Policy and Support Branch Communication Division. (ISBN: 978-92-5-106578-5, ISSN: 1020-1203).

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