EVALUATION OF WASTEWATER MANAGEMENT SYSTEMS IN ABUJA FOR SUSTAINABILITY AND DEVELOPMENT OF APPROPRIATE ENGINEERING STRATEGY
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2013-06
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Abstract
Environmental pollution due to improperly managed wastewater has been a major
challenge and of public health concern in Nigeria. Not many studies related to wastewater
management have been carried out in Nigeria, hence the paucity of data on wastewater
management in the country. The Wastewater Treatment Plants (WTP) in Nigeria's capital city,
Abuja are presently performing below capacity due to several problems. The aim of this study
was to evaluate the wastewater management system for Abuja and develop an engineering
strategy to improve it.
Six WTPs at Wuye lagoon, Gudu, Niger, Lungi, Mogadishu barracks and Sheraton were
assessed in comparison with the existing wastewater Master Plan of Abuja. The sites were
visited along with their sewer lines and manholes to assess their structural and environmental
engineering adequacy. Influent and effluent samples were collected weekly from these plants at
peak period in the morning hours (6.00 - 7.00am) in triplicates over six months period from
October 2007 to March 2008. These samples were analyzed for quality parameters such as 5-Day
Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), nitrate, nitrite,
sulphate, chloride, phosphate, and microbial content. Data were further analysed using ANOVA
at p= 0.05. Based on the evaluation, a suitable wastewater treatment plant was designed.
These WTPs are mini activated sludge treatment plants with submersible mechanical
aerators. Wuye lagoon has a capacity of 50,000 Population Equivalent (PE). Gudu, Lungi and
Mogadishu barracks have 6000 PE each while Niger and Sheraton have 3000 PE each. Average
reduction of BOD5 of 6±50.2%, 4±25.8%, 30±0.8%, 10.2±0.2%, 10.8±24.9% and 5±39.6% were
observed for Wuye lagoon, Gudu, Mogadishu, Niger, Lungi and Sheraton respectively. For other
evaluated parameters, average reduction in COD, nitrate, sulphate, chloride, phosphate and
microbial quality were 7.8±12.4%, 13.1±4%, 13.5±65.4%, 21.5±89.8%, 10.1±8.4% and
48±87.9% respectively. Sludge treatments significantly affect the physico-chemical parameters.
No regular aeration was carried out in the plants. In the satellite towns of Gwagwalada, Kuje,
Kubwa and Nyanya, there were no sewer facilities, hence septic tanks and soak-away pits were
constructed to handle the generated wastewater which is contrary to the provisions of Abuja
Master Plan. Non-biodegradable substances such as nylon and plastics were observed in
manholes. Discharge of evacuated septic sludge into sewer lines was the practice. A wastewater
treatment plant combining both natural and electromechanical system was designed (Design flow
of 2070 m3/d, BOD5 of 517Kg/day and Suspended Solids of 517.5kgSS/day). The treatment
plant using water hyacinth yielded nutrient removal of about 70.0% when power is not available
and enhanced treatment of up to 99.0% BOD removal when power is available.
The designed wastewater treatment plant using appropriate engineering strategy was
adequate and capable of solving the wastewater management problems of Abuja. The design
would be useful in other major cities in Nigeria.
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Keywords
Wastewater, Treatment plants, Management, Influent, Effluent, Sewer lines