DESIGN OF A CENTRAL WASTEWATER DISPOSAL SYSTEM FOR AN URBAN AREA USING FUTA CAMPUS AS CASE STUDY

Abstract

The research focused on the management of stormwater and sewage generated in a developed urban area - Federal University of Technology, Akure, Ondo State, Nigeria. This involved the design of sanitary sewers, stormwater collection networks and a central sewage treatment plant. The total estimate of the wastewater generated from various locations was 5.067 million litres per day based on the population of approximately 26,131. The existing sewage disposal system in use in the institution was the septic tank-soakaway arrangement for individual buildings. The design of the sanitary sewers and stormwater collection networks were based on the principles of hydraulics. The results obtained were used to analyze and design the drains and pipe sizes for the open channels and the closed conduits respectively. The size of the drains for stormwater collection networks was designed with the assumption of 0.75 and 1 meter width. Also, calculations were made for square drain (depth equals width) to be able to select practicable sizes. For optimum size solution, pipe size of 100 mm was found to be suitable for wastewater conveyance from the office areas. The sizes of pipes calculated for flows from residential quarters are too small, hence available commercial pipe sizes were selected. Wastewater samples were collected at various locations and were determined through laboratory tests to ascertain the concentrations of significant physical, chemical and biological content of the wastewater for proper selection of appropriate treatment processes. A BOD concentration of 350 mg/l and 353 mg/l obtained for residential and office areas respectively translated to high pollution load requires treatment before ultimate discharge into the receiving stream. The proposed sewage treatment plant was sited at the lowest topographical level, far enough from the office and residential quarters. This would allow flow by gravity from the various points. The sewage treatment plant components selected include screen chamber, grit chamber, skimming tank and rectangular/circular primary settling/sedimentation tank (PST), which are designed to optimal dimensions