Ozonation of refractory chemicals in leachate with hydrogen peroxide.

Nearly 97% of organic chemicals in Hong Kong leachate could be effectively removed by the UASB(upflow anaerobic sludge blanket) process followed by the fenton coagulation. The COD of leachate was lowered from an average of 12,900 mg/L to 1440 mg/L after the USAB treatment, and was further lowered to 394 mg/L after the fenton coagulation. The remaining refractory residues could be further removed by ozonation with the addition of H2O2. The ozonation for the supernatant of the fenton coagulation was most effective at pH 7-8, with the addition of 300 mg/L of H2O2, and 30 min of reaction. The final effluent contained only 85 mg/L of COD and 10 mg/L of BOD5. On the other hand, direct ozonation of UASB effluent lowered the COD to 905 mg/L and BOD5 to 103 mg/L. Ozonation improved the biodegradability of the organic residues, and also converted part of organic-N in the leachate into NH3-N and NO3(-)-N.