Technology Development For Landfill Leachate Treatment On The Basis Of AO~4 Biological Process

Landfilling has been the main disposable approach of municipal garbage, which always leads to leachate. Landfill leachate is pretty hard to treat efficiently and economically. However some kinds of popular processes like biological process integrated with membrane costs too much and puts our environment into second pollution risk as well. In order to solve these problems, we designed and verified that AO4 process removed nitrogen and carbon from leachate with medium landfilling age effectively and suited water quality fluctuation very well. It was found that treating leachate with kitchen waste biogas slurry increased nitrogen removal efficiency effectively. Based on this, AO4/SR-AOP/A/O/SR-AOP system was designed which made effluent meet Standard of municipal landfill pollution control (GB 16889-2008 table 2) in the end. The main results are summarized as follows:(1) Pre-denitrification and four-stage micro aeration process has been adopted to treat municipal landfill leachate. Partial nitrification and simultaneous nitrification and denitrification can be achieved in the whole process which led to 85%,99% and 87% removal efficiency of COD, ammonia and TN respectively. Effluent from AO4 was characterized with COD 500-1200 mg/L, ammonia lower than 25 mg/L, TN 100-280 mg/L. The results of quantitative PCR targeting at the ammonia oxidation and denitrification suggested that nirS counted much more than any other functional genes and had significant difference in abundance in each functional unit. Ammonia oxidizing bacteria (AOB) played a vital role in nitrification but ammonia oxidizing archaea (AOA) was in an undetectable level, while the abundance of nitrite oxidizing bacteria (NOB) was much lower, so the partial nitrification could be achieved steadily.(2) Co-treating landfill leachate with biogas slurry could enhance nitrogen removal efficiency of AO4 system apparently.8%(volume ratio compared to leachate volume) was confirmed the most optimal ratio adding biogas slurry to leachate which contributed to around 80 mg/L (40-100 mg/L) reduction of TN and about 200 mg/L (100-300 mg/L) augment of COD. So C/N of effluent increased from 3.6 to 8.0 and it helped to meet discharge limit finally.(3) Effects of pH, temperature and sodium persulfate concentration on SR-AOP in removing TOC and TN from the effluent were evaluated using response surface methodology. Results showed that the influential extent removal was more significant with pH, followed by temperature and sodium persulfate concentration. In addition, BOD5/COD ratio of the effluent could also be significantly improved after SR-AOP which laid a solid foundation of meeting discharge limit. Treating biological effluent under the optimal condition of 1 g/L sodium persulfate and 1 g/L FeSO4 at pH 5 and 25? for SR-AOP,40% COD and 10% TN were removed, then it was put into A/O system and second SR-AOP successively, the effluent water quality was COD 86 mg/L and TN 33 mg/L which met the Standard of municipal landfill pollution control (GB16889-2008 table 2).