Evaluation of Selected Municipal Decentralized Wastewater Treatment Plants for Condominium Houses in Addis Ababa, Ethiopia
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Date
2023-02
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Addis Ababa University
Abstract
One way removing the wastewater is to use decentralized wastewater treatment plant which is regarded as technologically simple, flexible management, and cost-effectiveness. Addis Ababa Water Supply and Sewerage Authority (AAWSA) implemented different technologies for decentralized municipal wastewater treatment system for 37 condominiums sites. However there has not been is no systematic study to evaluate performance of the different technologies in terms of removal efficiency performance for both physical and chemical parameters. Hence this research is made to generate a comparative efficiency evaluation for some selected technologies. In this study, (i) Membrane Bio-reactor (MBR), (ii) Waste Stabilization Pond (WSP) and (iii) Anaerobic Baffle Reactors (ABR) wastewater treatment technology were selected at six treatment plants. The performances of treatment plants were measured in terms of physico-chemical and bacteriological. Sampling was made monthly for three months in dry season in the period of December 2021 to February 2022 at a point ofinlet and outlet of treatment plants and the collected samples were analyzed and the overall removal efficiency were calculated. The treatment plants also compared by Multi-criteria Decision Making (MCDM) tool using Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The study revealed that there was statistical significance difference effluent between the wastewater treatment plants except nitrate (p<0.05, , two tailed) and MBR reduced BOD by 98%, COD 97% and TSS by 99%, the WSP reduced BOD by 85%, CODby84% and TSS by 89% and ABR reduced BOD by 30%, COD by 38%and TSS by 51%. Total coli form and E. coli were removed up to 99% for all treatment plants. However, the concentration of most effluents did not meet the discharge standards, MBR reduced BOD, COD and TSS to the level set by (EEPA, 2003) and WSP and ABR effluent did not meet the standard discharge limit. The wastewater quality index indicate the average of three months of wastewater quality index at Asko, Repi, Gelan and Mekanisa was unsuitable, at Bole Bulbula poor and at Kilinto good water quality was determined. Kilinto, Bole Bulbala and Mekanisa MBR were ranked 1, Gelan WSP was ranked 2, and Asko and Repi ABR were ranked the least.
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Anaerobic Baf le Reactors (ABR), Membrane Bio-reactor (MBR), Multi-criteriadecision making, Waste Stabilization Pond (WSP), Water quality index, Weighted ArithmeticMethod