Slow sand filtration of UASB reactor effluent: A promising post treatment technique

The study was carried out to evaluate the feasibility of slow sand filtration as a promising post treatment method for the up-flow anaerobic sludge blanket (UASB) reactor effluent. Laboratory scale filter column of 10 cm diameter and 0.54 m sand media depth was used to study the process performance. It was found out that slow sand filtration with 0.43 mm effective sand size is the most effective at a filtration rate of 0.14 m/h. It is capable of removing 91.6% of turbidity, 89.1% of suspended solids (SS), 77% of chemical oxygen demand (COD) and 85% of bio-chemical oxygen demand (BOD), 99.95% of total and fecal coliforms (TC and FC) and 99.99% of fecal streptococci (FS). Slow sand filters efficiently reduce the mass of suspended material and extend the filter run for more time (7 days) at a hydraulic load of 0.14 m/h as compared to the hydraulic load of 0.19 m/h and 0.26 m/h. Therefore, due to excellent effluent quality, it can be said that slow sand filtration would be a promising technology for the post treatment of small-scale UASB reactor effluent in developing countries, where treated effluent can be reused for various recreational purposes i.e. gardening and irrigation. as well as for safe discharge. (C) 2009 Elsevier B.V. All rights reserved.