AVAILABLE UV KILLING ESCHERICHIA COLI IN OXIDATION PONDS FOR COMMUNITY WASTEWATER TREATMENTThanit Pattamapitoon, Watcharapong Wararam, Pavin Wichittrakarn and Charinthip Soeihom
The available ultraviolet radiation (UV) to kill Escherichia coli (E.coli) was studied in oxidation pond of wastewater treatment system under the Royal Initiated Laem Phak Bia Environmental Research and Development Project (Royal LERD Project), Ban Laem district, Phetchaburi province, Thailand. The available UV radiation were found in 0-750 W/m2 range within 12 hours (06.00-18.00 oâclock). Hydraulic retention time (HRT) as 37 days was found 97.0% E.coli reduction efficiency. Amount of E.coli was significantly decreased 2.0Ã103 to 2.2Ã102 CFU/ml from sedimentation pond 1 to oxidation pond 2. On the other hand, there was no significant decreased from oxidation pond 2 to oxidation pond 3. The radiolysis process in term of hydrogen peroxide (H2O2) concentration were 1.9 and 2.2 Î¼g/l in oxidation pond 2 and 3, respectively. H2O2 can damage E. coli cell membrane and DNA. Therefore, it could be concluded that available UV radiation was the most important factor to reduce E.coli in oxidation pond of wastewater treatment.