PERFORMANCE EVALUATION OF A PILOT-SCALE PN/CD SYSTEM TREATING HIGH AMMONIA CONCENTRATION INDUSTRIAL WASTEWATER

Jun-Dar union wastewater treatment plant in Kaushung Taiwan provides wastewater treatment service for several petrochemical plants in Jun-Dar industrial park. The influent BOD5/COD ratio of this wastewater treatment plant averaged below 0.2 because wastewater has been treated biologically before discharged to the union wastewater treatment plant. The wastewater also contains high ammonia concentration and is low in COD/N ratio (close to 1.0). Existing treatment process is powder activated carbon technology process with wet air oxidation for activated carbon re-generation (PACT-WAR). So far, the treated wastewater can meet Taiwan EPA effluent discharge standard, but higher O & M cost pushes the treatment plant administration seeking more cost effective way to treat the wastewater.A pilot scale partial nitrification / complete denitrification (PN/CD) system was established on site to test its availability to treat the wastewater. Granular activated carbon was used as the media for attached biofilm. The packing ratio of both nitrification and denitrification tanks are 20% in volume. Two hydraulic retention times were tested in this study. Test results showed that PN/CD process can avoid over nitrification by controlling the flow rate to the nitrification tank. In this study, effluent pH and nitrate nitrogen concentration are better controlled than the existing PACT process. The averaged effluent COD concentration 112 mg/L under 4 hours HRT in denitrification tank and 8 hours HRT in nitrification tank. In order to meet discharge standard of effluent COD (