ASSESSMENT OF USAGE CONDITIONS OF SEPTIC TANKS IN HA NOI AND HAI PHONG
Keywords:environmental sanitation, septic tank, black water, grey water, desludging
The study had been conducted in 2017-2018 to generate usage conditions of septic tanks in Ha Noi and Hai Phong through (1) collecting information on usage condition of septic tanks by interview survey; (2) obtaining analytical results of wastewater inflowing to and out flowing from the septic tanks selected by interview survey results. The number of target interview surveys was 200 including both type of the septic tanks treating (i) black water only, and (ii) black and grey water. Among the septic tanks surveyed, 20 septic tanks were selected for collecting discharged wastewater sample and analysing discharged wastewater quality. The analysed parameters included water temperature, pH, BOD5, COD, TSS, Total Phosphorous (TP), Total Nitrogen (TN), NH4-N, and total coliform. Poor quality of wastewater discharged from septic tanks proved the inefficiency of septic tanks in treating black water from the households. As the results, desludging frequency of the septic tanks were recommended through the relationship between desludging interval and effluent water quality from septic tank. And the recommended volume of water-saving toilets was determined through the distributions of “water volume per flush in toilet”, “water consumption”, “estimated volume of septic tanks” and “desludging frequency” in Ha Noi and Hai Phong.
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