Optimizing Bio-sand Filter (BSF) for Maximum Thermotolerant Coliform (TTC) Removal from Drinking Water in West Bank

Abstract

There are about 297,900 Palestinian lives in 532 residential areas in Area c of Palestine (Jarrar, 2019). Many of them rely on rain harvesting into cisterns during winter to fulfill their needs of drinking water. For instance, in Massafer Yatta results of water quality from cisterns showed contamination levels that is ranging from 20-100 CFU/100ml. The Bio-sand filter (BSF) have been prompted extensively for water treatment in households in developing countries. In present study the influence of 9 operating parameters on BSF efficiency for Thermotolerant coliform (TTC) removal was investigated. Results analysis showed that 5 h residence time, and media age more than one month were significant with P-values of 0.0439 and 0.0089, respectively. Charge volume, turbidity and using different cistern to fill BSF had no significant influence. Although the 5 h residence time was significant, it was not sufficient to minimize TTC below the drinking water permissible level of 10 CFU/100ml when influent water had 500 CFU/100ml TTC. In addition to, the use of 5h residence time has led to a reduced filter age around 4 years, the filter efficiency to remove TTC started to gradually decrease after that. The use of sand of 0.18 mm effective size was significant with a P-value of 0.0016. While the temperature itself and inflow rate had no significant influence, the interaction of temperature and effective size was significant with a P-value of 0.0459. Elevated temperature up to 33 °C was found to negatively interfere BSF ability to remove TTC when the filter has effective size of 0.23mm. The influent TTC count had a positive significant effect on the effluent BSF TTC with a P-value of 0.0004. The use of 23h residence time showed the most significant influence among all operation parameters with a P-value <0.0001. The study concluded that the most important operation parameters for BSF to remove 99.8% TTC are 23h residence time and 0.18mm sand effective size. The study recommended to design a BSF that produces more than 20L to be used once every 23h and to replace the top of sand every 4 years at maximum. Optimizing Bio-sand Filter (BSF) for Maximum Thermotolerant Coliform (TTC) Removal from Drinking Water in West Bank International Journal of Research in Environmental Science (IJRES) Page | 29 software. The influence of 9 operating parameters on BSF efficiency for Thermotolerant coliform (TTC) removal was investigated. These parameters were residence time, charge volume, media age, turbidity, changing water source, temperature, sand effective size, influent TTC counts, and inflow rate.