Quality Improvement of Polluted River Water Used as Raw Water in Clen Water Supply by Using Biofiltration

Abstract

The river water pollution prevails in many parts of Indonesian region, due to the industrial, commercial, residential and farming activities. In many areas the quality standard of raw water has even been violated. This leads to the increased water treatment costs as well as public health risks. The use of biofiltration system can be an effective means to overcome these problems. The technology is able to eliminate various types of raw water contaminants and therefore reduces overall treatment costs. This paper demonstrates the technical and financial benefits of applying this technology as a pre-treatment step prior to conventional coagulation and flocculation processes. The experiments showed that bioreactor filled with "honeycomb" type matrix can reduce COD levels from 122-173 to 42-92 mg/L depending on the hydraulic retention time applied, while that filled with quartz sand can reduce COD levels from 128 to 32-43 mg/L. The biofiltration ,systems also demonstrated the ability to reduce TSS from 56 to 5 mg/L or equivalent to 90% reduction in the case of quartz sand matrix, while honeycomb-type matrix showed slightly inferior performance. The decrease in TSS will reduce coagulant consumption in the subsequent water treatment processes. It was also observed that nitrification also took place in the biofiltration system, indicated by removal of 55-75% ammonium concentration. This will eventually reduce chlorine required for disinfection. Based on these results, an estimation of potential cost saving from the use of the biofiltration process is derived.