Study On Efficiency Recovery Of Leachate Treatment By Semi-Aerobic Aged Refuse Biofilter

With the increase of municipal waste production in China,the production of leachate has also increased greatly.The landfill leachate has complex pollutants,high COD and ammonia nitrogen concentration,high salt ion content,high chroma and odor,which have become the key issues to be solved in the prevention and control of environmental pollution in waste treatment.Semi-aerobic aged refused bioreactor?SAARB?has both aerobic,anaerobic and anoxic environments,allowing most organic pollutants to be removed quickly.It also has a good effect on NH₄⁺-N treatment and low cost,so it has been widely studied and applied.The problem of actual leachate production above design value is widespread in China,which indicates that the actual leachate treatment facility will be under high load or even overload for a long time.Moreover,with the increase in the operation time of landfills,the amount of aged leachate that needs to be treated is also increasing.Compared with young leachate,aged leachate has higher salinity,more refractory organic matter,and a lower C/N ratio?mainly BOD/TN?,which is a great burden for continuously operating bioprocessors.However,there are few studies on the efficiency decay,pollutant accumulation and how to restore efficiency of SAARB that is continuously treated with high-load aged leachate.Leaching is an efficient,simple and cost-effective multi-component contaminated soil remediation method,it is also an important way to study pollutants and various ion leaching and exchange in soil.Based on this,the subject uses three SAARB indoor models to analyze the conversion of carbon and nitrogen pollutants,salt ions and 3D-EEM by continuous aged leachate recirculation,leaching and re-recirculation.In order to investigate the accumulation of salt ions and various carbon and nitrogen pollutants in SAARB,and the effect of leaching on the recovery of leachate efficiency under high-load treatment of SAARB.The results can provide a reference for the engineering application of the SAARB to treat leachate.During the first stage of recirculation,SAARB 2#pollutants and salt accumulation were less,and SAARB 1 and 3#pollutants and salt accumulation were more.In the case of continuous recirculate of aged leachate,the removal efficiency of pollutants in SAARB 1and 3#effluent is attenuated faster,and the removal efficiency of various pollutants in SAARB 2#effluent is attenuated slower.NH₄⁺-N removal rate is higher and the attenuation is lower in the whole stage,indicating SAARB has good removal of NH₄⁺-N.The accumulation of nitrate nitrogen and TN is relatively high,the TN removal rate is poor,treatment efficiency is greatly attenuated,and the salt accumulation leads to a gradual increase in N₂O emission flux.The above indicates that the treatment efficiency of the SAARB for continuous treatment of aged leachate is greatly attenuated.During the leaching process,,the substance represented by UV₂₅₄ is washed out more.When the effluent COD_Cr is not much different,the SAARB 1 and 3#chromogenic pollutants accumulate more than SAARB 2#.NH₄⁺-N accumulated in the mineralized waste bed is less,and even a part of the NH₄⁺-N in the domestic sewage for leaching can be removed.The concentration of NO₃^--N in the leaching water drops rapidly,and the content of organic nitrogen in TN is relatively high.SAARB accumulates a large amount of Cl^-in the treatment of leachate,and the leaching can effectively elute the accumulated salt ions and reduce the salt content in the SAARB.During the second recirculation stage after leaching,the COD_Cr,CN and UV₂₅₄removal rates of the SAARB are greatly improved.The COD_Cr removal rates of SAARB 1,2,and 3#increase by 17.82%,16.22%,and 15.60%,respectively,and the CN removal rates increase by 19.04%,5.39%,and 11.48%,respectively.UV₂₅₄ removal rates increase by28.29%,14.00%,and 18.18%.The UV₂₅₄ removal rates increase the most,probably because the recovery of adsorption is greater than the degradation activity of microorganisms affected by salinity.The removal rate of NH₄⁺-N is above 98%,and the concentration of NO₃^--N is greatly reduced,indicating that the leaching increases the activity of denitrifying bacteria.The lifting effect of TN removal is also obvious,and the N₂O emission flux is much smaller than the end of the first recharge.After the leaching,the accumulation of Cl^-ions in the SAARB has been relatively small,so the salt of the leachate has a strong interception.In general,leaching has a good recovery in SAARB treating aged leachate effect.