Study On Treatment Of Landfill Leachate Using Anaerobic Digestion And SNAD-MBBR

With the increase in the annual production of municipal solid waste,the amount of landfill leachate generated during landfilling is also increasing year by year.The landfill leachate,which contains high concentrations of organic matter and ammonia nitrogen,is very hard to disposal.In this paper,the anaerobic digestion and SNAD(simultaneous nitritation,anaerobic ammonia oxidation and denitrification)-MBBR process,was designed to treat landfill leachate.Firstly,the process parameters and startup strategy during start-up period were investigated through lab-scale experiments.Secondly,the effect of the landfill leachate treatment performance was investigated.Finally,the feasibility of this combined process for landfill leachate treatment was analyzed through the actual full-scale project for treatment of similar wastewater.The following conclusions are as follows.1)At temperature of 33~36°C,pH of 7.3~8.0,stirring speed of 20 r/min,anaerobic digestion process can be quickly started.In the subsequent SNAD process,with HRT of 18 h,temperature of 33~36°C and dissolved oxygen(DO)controlled at 0.2-0.4 mg/L,the NOB(nitrite oxidation bacteria)was eliminated by adjusting the concentration of free ammonia,but the AOB(ammonia oxidation bacteria)was enriched in the reactor.Therefore,the nitritation process was started firstly.Afterwards,with anaerobic ammonia-oxidizing bacteria and MBBR carriers adding to the reactor,and some organic carbon sources adding to the influent,the DO in this reactor was decreased to 0.03-0.1 mg/L,the SNAD process was started.Through the above-mentioned strategies,the SNAD-MBBR process could be accomplished in90 days.2)During the treatment for real landfill leachate by anaerobic digestion and SNAD-MBBR process,under the stable operational conditions,the total nitrogen load reached 0.53 kg TN/m~3·d and the COD load reached 2.7 kg COD/m~3·d,with removal efficiencies of TN and COD reached 89%and 93%,respectively.3)In a full-scale projest,landfill leachate with excess sludge of municipal wastewater treatment plant are mixed with a volume ratio of 1:2,most COD of the mixture are removed by anaerobic digestion firstly,then nitrogen were removed by subsequent SNAD-MBBR process.300 m~3 of landfill leachate per day was treated,with the maximum total nitrogen removal rate of 0.43 kg TN/m~3·d,and the total nitrogen removal efficiency of 80%.