Evaluation of Dolochar as a Filter Media in Slow Sand Filtration

Abstract

The study was carried out to evaluate the feasibility of slow sand filter using dolochar, a solid waste generated from sponge iron industry, as a filter medium along with the sand to treat secondary treated wastewater effluent. Effectiveness of the slow sand filters were assessed using two laboratory-scale filter columns (0.10 m diameter and 0.50 m media depth), one consisting of sand media and the other with sand and dolochar (dual media filter). The effective size of sand and dolochar used were 0.41 and 0.53 mm to study the performance at a filtration rate of 0.10 m/h. For the 280 h of run period, dual media filter showed higher removal efficiencies in all respects, especially average chemical oxygen demand (COD) removal of up to 80.96% compared to 64.68% of sand media filter and turbidity removal of 91.13% compared to 82.27% of sand media filter. The phosphate and total suspended solids (TSS) removal efficiencies of dual media filter were 78.69 and 89.08%, whereas in case of sand media filter removal efficiencies were 66.17 and 82.48% respectively. Microbial removal efficiency observed was also more in the case of dual media filter. The only disadvantage in dual media filter observed for having more head loss which affects the filter run. Since the filter having dolochar exhibited to possess higher removal efficiencies, it supports the utility of dolochar as a low-cost and highly efficient filter media.