Studies Of Landfill Leachate Treatment By Photochemical Oxidation Process

In this dissertation, laboratory experiments were conducted to compare the efficacies to treat stabilized landfill leachate, by several photochemical oxidation processes, such as UV/H2O2, UV/O3, and UV/H2O2/O3. The leachate came from a municipal sanitary landfill located in northwest China and the average values of its main parameters were: pH8.2; COD2628mgL-1; BOD5430mgL-1; NH3-N3100mgL-1. NH3-N of raw leachate was initially desorbed at pH11.0, and then the photochemical oxidation processes were applied. The results showed only 18~27%COD removal was reached by UV/H2O2 with hydrogen peroxide doses between 1 and 8gL-1, however, 55~80%COD removal was obtained by UV/O3 with an ozone dosage of 3.5gL-1, and 65~86%COD removal was achieved by UV/H2O2/O3 with an ozone dosage of 3.5gL-1 in the presence of hydrogen peroxide doses between 0.35 and 3.5 gL-1.Biodegradability of landfill leachate, measured as BOD5/COD, increased from less than 0.19 to nearly 0.4 by UV/O3 with an ozone dosage of 450 mgL-1. UF separation showed that the predominant COD distribution before and after UV/O3 oxidation were higher than10KD(>83%) and lower than 3KD(>98%) respectively, which revealed the significant reduction of nonbiodegradable organic matters of leachate. In addition, results of Batch Activated Sludge processes treatment showed a substantial argument for the increase on biodegradability of oxidized leachate, which demonstrated that UV/O3 would be beneficial to the subsequent biological treatment processes.A Pseudo-first-order kinetics model for COD removal by UV/O3 was proposed and proved.