PILOT-PLANT EXPERIMENTS FOR IMPROVEMENT OF POLLUTED CANAL KLONG WATERBY ROCK-BED FILTRATION/

Applicability of the rock-bed filtration technique was investigated th rough pilot-plant experiments in Bangkok, Thailand. Polluted canal wat er was used as horizontal flow influent to two reactor channels filled with rocks. During one year operation, HRT, filter media, and aeratio n mode, were changed in several runs. The results showed that 1) the r ock-bed filtration with aeration and the HRT more than 6 h can success fully improve polluted klong water by reducing the pollutants (e.g. 60 -120mg/L of SS to 20-40 mg/L and 15-30 mg/L, of BOD to 5-20 mg/L); 2) main removal mechanism seems to be the sedimentation resulting from th e settleability enhanced by aeration, and the biofilm attached onto ro cks also works in the reduction of soluble organic matter; 3) a combin ation of three rock sizes arranged in descending order showed best res ults; 4) longer HRT (13 h) produces better effluent but is not so effe ctive if it exceeds 9 hours; 5) 60-70% of sediment IL was decomposed i n a year, and porosity in rock beds reduced approximately 16%. (C) 199 7 IAWQ. Published by Elsevier Science Ltd.