Experimental Study On The Treatment Of Aged Landfill Leachate By CANON Process

The composition of leachate in old landfills is complex and the water quality fluctuates greatly.It is an extremely difficult wastewater to treat.At present,the commonly used leachate treatment technologies mainly include biochemical treatment,membrane separation technology,advanced oxidation,incineration evaporation technology,etc.Among them,the biochemical treatment method has the characteristics of low cost,convenient operation and management,and good treatment effect.In the biochemical method,the full autotrophic biological nitrogen removal?CANON?process based on anaerobic ammonia oxidation?Anammox?is the most cost-effective biological nitrogen removal process currently known.However,due to the long start-up period of the process,the difficulty of inhibiting nitrifying bacteria,the lack of in-depth mechanism research,and the difficulty in enrichment and cultivation of anaerobic ammonia oxidizing bacteria?An AOB?,it has severely restricted the promotion and development of the process.In this study,the actual aged landfill leachate was used as the treatment object.The CANON pilot test was carried out,and domesticated culture of short-range nitrifying bacteria and An AOB was conducted.The cultivated two bacteria were used to start and operate the CANON pilot reactor.The start-up characteristics,operating efficiency,and control conditions of each system were compared and analyzed using high-throughput sequencing technology on the bacterial strains of the short-term nitrification and anaerobic ammonia oxidizing bacteria in the aged landfill leachate and laboratory artificial water distribution culture.Under the conditions of room temperature and high ammonia nitrogen,the DO was controlled to 0.5?0.7 mg·L^-1,and the short-range nitrification pilot reactor was successfully started in 101 days.Under the condition that the concentration of NH⁺₄-N in the influent was500 mg N·L^-1,the removal rate of NH⁺₄-N reached 98.15%and the accumulation rate of NO₂^--N was 89.48%.During the start-up operation,the combined action of FA and FNA was used to inhibit the growth of nitrite oxidizing bacteria?NOB?,and control the sludge age to eliminate NOB in the reactor.The results of high-throughput sequencing showed that Nitrosomonas was the bacterial species in the short-term nitrification reactor of aged landfill leachate for in-water culture,and its abundance was 11.67%.The anaerobic ammoxidation reactor used MBBR K3 filler as the carrier for the domestication of An AOB.It took 376 days to successfully cultivate a pilot scale anaerobic ammonia oxidizing bacteria,and the total nitrogen volume removal load reached 0.10 kg N·(m^-3·d)^-1.The high-throughput sequencing results showed that compared with the simulated wastewater,the anatomox reactor in which the old landfill leachate was used as the in-water culture was richer in diversity,and the bacterium that performed anaerobic ammonia oxidation was Candidatus Kuenenia.Scanning electron microscopy?SEM?was used to observe the sludge in the successfully started Anammox reactor,and the sludge morphology clustered together in a spherical shape could be clearly seen,which further proved that An AOB was successfully cultivated.The CANON pilot test adopts intermittent aeration-continuous stirring operation mode.After 58 days of cultivation,the reactor was successfully started.The ammonia nitrogen volume load of the feed water was 0.09 kg N·(m^-3·d)^-1,NH⁺₄-N and TN.The removal rates reached 96.80%and 85.88%,respectively.Adjust the aerobic and anaerobic time of the reactor according to the change in p H during the reaction to optimize the CANON pilot process.Under the condition of increasing the influent NH⁺₄-N load,the removal rates of NH⁺₄-N and TN can reach 98.18%and 86.45 respectively%.The CANON pilot test has proved that the CANON process can treat aging landfill leachate,and a CANON pilot test process is performed for this purpose.The CANON pilot reactor uses continuous water inflow-continuous aeration operation mode.The reactor was successfully started in 150 days.Under the conditions of NH⁺₄-N and TN concentrations of 223.00mg·L^-1and 227.00mg·L^-1,the removal rates of NH⁺₄-N and TN reached 87.44%and 74.01%,respectively..The test results show that when DO is controlled at 0.7±0.1 mg·L^-1,short-range nitrification and anaerobic ammonia-oxidizing bacteria can work simultaneously and efficiently in the CANON process.This study successfully cultivated the CANON process by cultivating short-range nitrification and anaerobic ammonia oxidizing bacteria to provide seed mud for the CANON pilot reactor,and contributed to the application and promotion of the CANON process in practical engineering.