Landfill Leachate Treatment By The Sequencing Batch Biofilm Reactor Of One-single Autotrophic Nitrogen Removal

With the rapid development of urbanization,the amount of municipal domestic waste grows at the rate of 8%～10% per year. Sanitary landfill is the main method of current municipal domestic waste disposal in our country. Landfill leachate forms in the process of sanitary landfill. Landfill leachate contains high concentration of ammonia nitrogen and COD, low C/N ratio, low pH, and the quality and quantity of it changes largely. So the treatment of landfill leachate becomes a hot and difficult. Physicochemical and biochemical methods can remove nitrogen in the landfill leachate. The air ammonia stripper method and chemical precipitation are the main methods of the physicochemical method. The traditional methods of biological nitrogen removal adopted nitrification and denitrification technology, but biological nitrogen removal of landfill leachate is not easily. In this experiment, we treat landfill leachate with a sequencing batch biofilm reactor. This experiment is completed via two steps, the partial nitrification stage and the single autotrophic biodenitrification stage.During the partial nitrification stage, we use the synthetic wastewater made in the laboratory to acclimating the activated sludge. We used four sequencing batch biofilm reactors.The sludge acclimatization stage lasted 100 days. During the stage, with the time increasing, the concentration of COD was decreasing.The conversion efficiency of ammonia nitrogen was increasing, up to 97.3%,94.5%,96.1% and 95.4% after 100 days,respectively. The accumulation rate of nitrite nitrogen was increasing, up to 80.9%,73.9%,77.0 % and71.8% after 100 days, respectively, and the accumulation rate of late stage rose slowly. During the single autotrophic biodenitrification stage, we mainly discussed the influence of the temperature, pH, DO and the mode of operation to the system. The results showed that the best operating temperature was about 35℃, DO was about 1.5mg/L, pH was about 8, 12 hours for a cycle (2.5 hours was aerobic, 1.5 hours was anaerobic). We also monitored COD and nitrogen, and the results showed that the removal rate of COD was about 10% and the conversion of ammonia nitrogen was above 90%. The four reactors running stably. By using PCR-DGGE technology, we detected the microbe of the aerobic activated sludge before domestication, the sludge after domestication, the sludge of the single autotrophic biodenitrification stage and the precipitate of landfill leachate. We studied the changes of the microorganism communities in the reactor. The results showed that, the microbe in the precipitate of landfill leachate is the more. During the partial nitrification stage, the microorganism communities were very few and most of them were autotrophic microbes because of the synthetic wastewater. But during the single autotrophic biodenitrification stage, because of the the mode of operation and with the landfill leachate into the reactor, microbes increased. The changes of the microorganism communities and the analysis of the experiments of nitrogen removal are in substantial agreement.