.

By:

Najib B. Lukoyaa (PhD Candidate)

BOKU, VIENNA AUSTRIA

Wastewater pollution attenuation in a tropical urban

wetland system: Nakayiba, Masaka, Uganda

Introduction

Materials and Methods

Results and Discussion

Conclusion and Recommendations

Presentation Outline

Wetland ecosystems have demonstrated a key role in treatment and/or polishing of

wastewater from Urban systems of East Africa (Co´zar et al. 2007; Kansiime et al. 2007a; Kansiime et al. 2007b; Kivaisi 2001; Kyambadde et al. 2004...etc)

Natural wetlands are under threat in the region due to; High Population, Urbanisation,

Agriculture, Industrialisation The impact of wetland degradation on the water quality regulation function has been

reflected and demonstrated by Lake Victoria Key drivers regarding wetlands degradation and water quality deterioration in the Lake Victoria basin

(East Africa)

Increasing Population

Rapid Urbanisation

Industrial development

Increase in wastewater quantity (discharged with inadequate or no treatment)

Introduction

Introduction-Cont’d

Population density (persons/sq km) – Impacts on lake buffer zone and water quality

Source; LVBC, 2010

Introduction-Cont’d

Wastewater treatment systems: Inadequate in terms of network coverage and treatment

efficiency

Municipal wastewater

Storm water from catchment

Industrial wastewater

Inadequate conventional WWTP

Surface water pollution-

Eutrophication

Risks and vulnerability to

communities-public health

Study Objectives and Rationale

Wetland pollution buffers in the Lave Victoria basin like Nakayiba (Masaka, Uganda) are

key landscape ecosystem features Most importantly, they offer municipal wastewater treatment systems, a low cost but

valuable polishing role coupled with a public health risk reduction due to potential surface and ground water pollution

The main objectives of this study were to;

Characterise the Masaka conventional Wastewater Treatment Plant (WTP) effluent quality

Assess the potential pollution attenuation through Nakayiba Wetland.

Broad Hypothesis: Degradation of the Masaka WTP infrastructure over the years has resulted into a decline

in treatment efficiency hence poor effluent quality. Nakayiba Wetland provides an effective natural pollution buffer Policy implication: Integration of wetland systems in planning urban landscapes to enhance effective

wastewater treatment and water quality regulation

Methods – Study Area: Masaka WWTP and Nakayiba

Wetland

Methods – Study Area: Masaka WWTP and Nakayiba Wetland

Methods – WWTP Effluent Characterization

Many Parameters used to characterise Wastewater – Few prioritised in East Africa due to

analytical limitations

Masaka WWTP effluent monitoring data was obtained from the National Water and

Sewerage Corporation (NWSC) (2008-2012).

Routine WWTP performance monitoring parameters:

pH, Electical Conductivity (EC), BOD, COD, Total suspended solids (TSS), and

Ammonium Nitrogen (NH4-N). Faecal coliform (many gaps)

Parallel analysis carried out during research period (2012-2013) To verify methods and

potential error limits

Rainfall data from local meteorological station (Kitovu-Masaka) obtained to characterise

seasonal variations and potential dilution effects

Methods – Downstream wastewater quality changes

Sampling points:

WWTP Effluent ; Upstream;

Effluent-Wetland confluence;

Three points down stream (WET

1, WET 2, DWN-outlet)

Parameters: Temp, pH, EC, BOD,

COD, TSS, feacal coliform, NH4-

N, TN, TP, PO4-P

Methods:

Temp, pH, EC (Probes on-site)

BOD, COD, TSS, NH4-N, TN,

PO4-TP,TP, feacal coliform

(standard methods-APHA, 1995

as adopted at NWSC laboratories)

Results – Effluent Characterization

Masaka WTP effluent did not meet the National Environment Discharge (Wastewater)

standards almost during the entire five years of the analysis period – for all key parameters

Mean effluent concentrations (Mean ± SE mg/l)

BOD5 (333.7 ± 32.0) standard 50mg/l

COD (666.9 ± 42.1) standard 100mg/l

TSS (346.6 ± 25.3) standard 100mg/l

NH4-N (55.73 ± 3.72) standard 10mg/l

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

CO

D m

g/l

0

200

400

600

800

1000

1200

1400

16002008

2009

2010

2011

2012.

Standard 100mg/l

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

BO

D5 m

g/l

0

200

400

600

800

1000

2008

2009

2010

2011

2012.

Discharge Standard 50mg/l

Results: Effluent Characterization- compliance with discharge standards

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

N-N

H4

mg/l

0

20

40

60

80

100

120

1402008

2009

2010

2011

2012.

Standard 10mg/l

Results: Effluent Characterization-seasonal effects

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

N-N

H4 m

g/l

20

30

40

50

60

70

80

90

100

Rain

fall

mm

0

20

40

60

80

100

120

140

160

180

N-NH4

Rainfall

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Ele

ctr

ical C

ond

uctivity u

s/c

m

1400

1600

1800

2000

2200

2400

2600

2800

Rain

fall

mm

0

20

40

60

80

100

120

140

160

180

Electrical Conductivity

Rainfall

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Co

nce

ntr

atio

n m

g/l

0

200

400

600

800

1000

1200

Ra

infa

ll m

m

0

20

40

60

80

100

120

140

160

180BOD

COD

Rainfall

TSS, BOD and COD – no clear

pattern (not significant).

Other factors influence –

external inputs from the town

unpredictable

Results: Pollution attenuation through the wetland

Despite the dilapidation in wastewater treatment performance,

Nakayiba wetland showed effective downstream pollution

attenuation through reduction of;

Organic matter,

Suspended solids,

faecal coliform

Nutrients (TN and TP)

Results: Pollution attenuation through the wetland-overall removal efficiency

Sampling site Cond. µs/cm pH BOD mg/l COD mg/l TSS mg/l TP mg/l O-PO4 mg/l NH4-N mg/l TN mg/l FC (log10)

Upstream 98.3±24.2 6.9±0.2 12.4±1.8 37.9±2.8 37.6±4.1 1.95±1.13 0.48±0.33 0.66±0.15 3.20±1.11 1.91E+03±7.79E+02

Effluent 1415.7±130.2 7.4±0.1 256.1±27.0 622.0±51.0 426.1±58.5 37.10±15.07 17.78±1.58 65.43±6.85 78.55±7.64 2.18E+09±8.88E+08

Wet 1 863.6±169.2 7.3±0.1 63.1±9.1 213.2±35.8 127.8±24.2 15.82±5.24 7.30±1.43 28.77±5.24 42.71±6.76 3.52E+06±1.44E+06

Wet 2 911.2±93.2 7.4±0.1 64.5±10.1 220.7±20.4 83.3±13.0 17.21±4.74 8.44±2.13 26.47±4.64 32.78±4.89 1.36E+03±5.57E+02

Downstream 300.2±43.5 7.0±0.1 35.2±2.4 109.5±21.0 76.4±7.4 5.81±2.53 2.27±0.63 4.51±1.55 16.24±2.20 1.43E+02±5.82E+01

Removal

Efficiency

(%) N/A N/A 86.3 82.4 82.1 84.3 87.2 93.1 79.3 99.9

Results: Pollution attenuation

through the wetland-overall removal

efficiency

Sampling site

Upstream Effluent input Wet_1 Wet_2 Downstream

Concentr

ation m

g/l

0

200

400

600

800

BOD

COD

TSS

Sampling site

Upstream Effluent input Wet_1 Wet_2 Downstream

Co

nce

ntr

atio

n m

g/l

0

20

40

60

80

100

TN

NH4-N

Sampling site

Upstream Effluent input Wet_1 Wet_2 Downstream

Co

nce

ntr

atio

n m

g/l

0

10

20

30

40

50

60

TP

PO4-P

Conclusion and recommendations

Masaka WWTP serves only 8% of the municipality and its effluent does not

meet discharge standards

Nakayiba wetland effectively buffers the Masaka WTP performance

This is essential in enhancing downstream pollution control as well as

safeguarding potential public health constraints.

It is therefore recommended that;

Masaka WWTP requires rehabilitation and expansion of the town sewage

network

Masaka Urban landscape plan needs to critically consider Nakayiba as a key

ecosystem for Municipal sanitation and wastewater management

Acknowledgement s to ADC , NWSC and Assoc. Prof.

Thomas Hein (WCL/BOKU)

Thank you for your attention