Consequences of fluctuating depth of filter media on coliform removal performance and effluent reuse opportunities of a bio-sand filter in municipal wastewater treatment

Abstract

Abstract Due to the rapid urbanization attaining full coverage of proper wastewater treatment is a challenge in several developing nations. The conventional sanitattion approachpracticed in different countries does not satisfy the current wastewater treatment need of fastly growing cities. Also, the decentralized technologies practiced so far is interrupted by technical issues that ends in an extensive upsurge of maintenance cost and poor effluent quality. Thus, this study focuses on the applicability of low-cost bio-sand filters as a decentralized municipal wastewater treatment technology through testing pathogen removal efficiency and effluent reuse possibilities of different media depth bio-sand filters. Three setups of bio-sand filtercolumn were established each comprised of a specific sand, fine gravel and coarse gravel with different filter depths. The results orevealed geometric mean reductions for total coliforms of 99 %, 87 % and 30 % for a bio-sand filter with the top fine sand depth of 220 mm, 120 mm, and 20 mm, respectively. While the geometric mean for the reduction of fecal coliform was 99.9 %, 99.6 %, and 99 %. The effluent from three of the bio-sand filters does not achieve the requirements for unrestricted irrigation according to WHO and US-EPA guidelines. Whereas the quality of effluent from the first scenario of the bio-sand filter can meet WHO and US-EPA guidelines for restricted irrigation reuse option. Likewise, the effluent from the second scenario of the bio-sand filter achieves the US-EPA reuse standard for restricted irrigation.