Comparative Study On Treatment Of Landfill Leachate With Regional Biological Filter Reactor And Regional Constructed Wetlands

Traditional technologies have poor treatment efficiency in landfill leachate,due to complex compositions,imbalanced nutritional ratios,poor biochemical properties,and high pollutant concentrations of landfill leachate.Based on this,two processes,including an integrated biofilter reactor and horizontal flow constructed wetland?HFCW?reactor,were used to treat landfill leachate in this study.The concentration changes of influent and effluent under different conditions were monitored periodically and the operating parameters were optimized to compare the effect difference of two crafts..In order to explore the removal mechanism of pollutants in different sections and contribution of different purification path ways to pollutant removal,the periodical changes,course changes,microbial activities and structure of microbial species in different sections were monitored during the stable period of each operating condition..Finally,the paper suggested that the integrated biofilter reactor and HFCW reactor should be used for the development region and the undevelopment region for treating landfill leachate based on comparing the treatment effect and economic cost of two processes.This study could provide some useful references and guidances for the practical engineering when the landfill leachate is need to treat.The main results and conclusions are as follows:?1?The integrated biofilter reactor was used to treat the landfill leachate,under the condition that HRT was 12 h and the actual landfill leachate was diluted as influent in a continuous operation.The organic matter load and nitrogen load of the reactor were started from 1.60 kg COD?m³·d?^-1 and 0.40 kg TN?m³·d?^-1,to 4.80 kg COD?m³·d?^-1and 1.20 kg TN?m³·d?^-1 gradually.The integrated biofilter reactor could efficiently remove COD,TN and NH₄⁺-N from the landfill leachate under different conditions after the reactor was runned stably.Under the maximum load,the removal rate of COD,NH₄⁺-N and TN could reach 87.82%,89.91%and 86.63%,respectively.?2?In the integrated biological reactor,the ammonia utilization rate?AUR?,nitrite utilization rate?NUR?,activity of anammox bacteria?SAA?and the denitrification rate?DNR?of the microorganisms at the same location increased with the increase of the reactor load.The AUR and NUR of activated sludge?at the bottom of reactor?were higher than those in the biofilm at 40 cm of the reactor;as the reactor height increased,while the SAA of the biofilm increased and the DNR decreased with the increased height.?3?Concentration changes of the pollutants and identification of microorganism strains along the integrated biological reactor showed that partial nitrification mainly occurred at 0-40 cm of the reactor,and its functional bacterium was AOB,among which the main strain was Nitrosomonas,accounting for 11.37%and 12.70%of the relative abundance in the activated sludge zone?bottom?and the biofilm zone?40 cm?.On the other side,ANAMMOX mainly occurred at 80-160 cm of the height,and the functional bacterium was AnAOB,where Candidatus Brocadia was the main strain,accounting for 4.42%and 6.61%of the relative abundance in biofilms of 80 cm and 120cm.?4?Horizontal flow constructed wetland?HFCW?reactor was used to treat the landfill leachate.The HRT was 30 d,and the influent was actual landfill leachate dilution.The influent mode was pulse.When the NH₄⁺-N_infnf and COD_inf were 204.65mg·L^-1 and 795.12 mg·L^-1,the reactor could achieve effective removal of COD,BOD₅,and NH₄⁺-N from the leachate in both continuous and intermittent aeration modes after the reactor was stable,corresponding removal rate were 82.56%?81.41%?88.04%.?5?The high-frequency intermittent aeration?aeration 6 h:non-aeration 6 h?of HFCW had significantly better treatment effect than low frequency intermittent aeration?aeration 12 h:non-aeration 12 h?on the landfill leachate when the HFCW reactor was used to treat landfill leachate under the same on-off ratio.As the same time,the removal rates of COD,BOD₅,NH₄⁺-N and TN in the landfill leachate were 88.76%,90.75%,91.90%and 82.07%,so that the effluent concentration of carbon and nitrogen could meet the Standard for Pollution Control of Domestic Waste Landfill?GB16889-2008?.?6?Considering the pollutant removal efficiency and investment-operation cost between two processes,the integrated biological reactor had better treatment effect,and the HFCW had lower investment-operation cost.So the integrated biological reactor was more suitable for the treatment of landfill leachate in economically developed areas,and HFCW was more suitable for the treatment of landfill leachate in remote undeveloped areas.