The efficiency of Kirinya water the stabilization ponds in the sewage treatment process.
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Management of sewage in Uganda is a mandate of National Water and Sewerage Corporation and involves all activities of collection, transportation and treatment of raw sewage before discharge to the environment. It has, however, been observed that urban sewage management still faces a number of challenges which have hindered the achievement of national sanitation objectives. The population estimate of Jinja city is 300,000 as of October 2020 (Daniel, 2020). The Kirinya water stabilization ponds were serving population of about 28,000 (1996 estimates) people at the time of construction, receiving about 4,400m3 of waste water per day. With the current population of Jinja which is almost 10 times the 1996 estimates and the overwhelming amount of raw sewage produced in the Jinja city of about 700,000m3 of sewage water produced annually due to urban development, industrialization and population growth, it is thoughtful to question the efficiency of the target treatment plant, the Kirinya water stabilization ponds. The study undertaken was evaluating the efficiency of Kirinya water stabilization ponds in Jinja district on treating domestic and municipal waste collected by NWSC. Samples in triplicates for analysis of, BOD, COD, TSS, and Total Phosphorus were taken from every pond as well as the raw sewage comparing the results with the national standards. At each sampling site, dissolved oxygen (mg L-1), temperature (o C) and water conductivity (µS cm-1) were measured in situ at surface using Multiprobe (YSI). All spetrotomphoetric determinations were made using an Aquamate spectrophotometer (Thermo Electron Corporation, UK Model No. 300).The results obtained from the study imply a close adherence of the sewage effluent to the national standards for of the investigated parameters. There was a 77% removal of Total phosphorus, 40% adherence to the standard Dissolved oxygen, 60% BOD and 72% COD reduction in the waste water. EC levels in the sewage were reduced by 24% and TSS reduction of 90%. However the results showed over loading of the lagoon system due to the large amounts of sewage fed into the system for treatment, for example the anaerobic and facultative ponds responsible for the BOD and COD reduction scored 60% and 72% instead of 95% and 80% respectively. The Kirinya water stabilization ponds have a capacity of 60% as per the results of the study and a 40% shortfall of the treatment process by the stabilization ponds. This 40% failure could be attributed to the small size of the ponds receiving large amounts of sewage and limited hydraulic retention times for the sewage in the individual units which makes the sewage less available for decomposition. With the current 40% failure of the system and the subsequent overload of the Kirinya lagoons due to a drastic population growth in the country and in Jinja city, there is likely to be a system breakdown in the sewage treatment process in Kirinya NWSC sewage treatment plant if no intervention is inaugurated.