Decentralized waste water treatment by vermifiltration using river bed material

Abstract

Rural sewage treatment is now paid more and more attention in India. The high cost of wastewater collection and wastewater (WW) treatment is not permitting the conventional sewage treatment plant in small areas, so cost effective decentralized and eco-friendly treatments are needed. Vermifiltration needs no external energy (except pumping), is low cost, and produces no sludge; hence vermifiltration can be very useful for small communities, colonies and villages. The present study was carried out to get optimum Hydraulic loading rate (HLR) for vermi filter to achieve the requisite quality of effluent. In the present study, there were two reactors and these reactors were in triplicates. One set of the reactors (vermifilter) was inoculated with earthworms (E.fetida) and other set contained only filter material without earthworms (geofilter).The laboratory model consisted of plastic containers filled with the filter materials in four layers: gratings at the top and then gravel of two different sizes in two layers and supporting layer of larger size gravels. The wastewater was applied to the filters at four rates: 1.5, 2, 2.5 and 3.5m3/m2/d. The effluent from vermifilters and control were analysed for physico-chemical and biological parameters. Maximum removal of organic matters in vermifilters was at 2.5 m3 m-2 d-1. At this rate, BOD, COD, TSS and TDS removal was 96%, 89%, 90%, 82% respectively. The treated effluent and vermicompost both were rich in nitrate, phosphate and hence both could be used in agriculture.