Performance of Lab- scale Filtration System for Greywater Treatment and Reuse: A Case of College of Natural and Computational Science Campus, Addis Ababa University, Ethiopia
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Date
2020-07-04
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Addis Ababa University
Abstract
Greywater management through treatment using filtration systems and reuse is one way to achieve water security in Ethiopia. The College of Natural and Computational Sciences (CNCS) campus of AAU is facing the problem of water shortage especially in the evening hours when normal water supply is cut off resulting into poor sanitation. Reusing greywater (GW) that comes from dormitories for non- potable uses is one of the options to supplement water supply. The pollution levels of GW is quite low as compared to black water. This quality allows greywater to be treated by simple treatment technology like filtration. The aim of this study was to evaluate the performance of a lab- scale filtration system for greywater treatment and reuse using sand and granular activated carbon as filter media. The specific objectives of this study were to: 1) Characterize the raw greywater generated at CNCS campus; 2) Compare the treatment efficiency of lab-scale filtration systems that use gravel + sand and gravel + sand + GAC; and 3) Evaluate willingness to use treated greywater for selected non-potable uses. Raw greywater quality was characterized by determining its physico-chemical and microbiological parameters in the laboratory. The treatment efficiency was determined by comparing the mean values before filtration and with those after filtration. The systems was examined for its efficiencies at different hydraulic retention times (HRT) (12, 24, and 36 hrs) and at different filter columns, one with gravel + sand and the other with gravel + sand + GAC operating at constant HLR (0.15m/h). The willingness to use treated greywater for selected non-potable uses was evaluated through interviews (using questionnaire). Results showed that the raw greywater was polluted and was above reuse standards except nitrates and Total phosphorus, therefore treatment was necessary. For both filter columns, the treatment efficiency of the system increased with HRT at 12 h and 24 h and later on it decreased at 36 h, except for EC and NH4-N, which decreased with increase in time. The removal of contaminants was significant higher (p < 0.05) at 24 h and with no significant different (p > 0.05) between filters except in removal of NH4-N. The pollution reduction was from 60.8 % - 100 % for selected parameters (pH, turbidity, EC, BOD, COD, NH4-N, NO3, TP, TC, and FC) in filter column B and from 47.2 % - 100 % for filter column A. The results also indicated that over 80% of the respondents were willing to use the treated greywater for selected non-portable uses, for the fact that the treated greywater was meeting the reuse standards. Thus, a filtration system is efficient and can be employed to treat GW for non-portable uses at CNCS to improve hygiene, sanitation and water shortage.
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Keywords
Greywater, Filtration System, Filter Columns, Hydraulic Retention Time