Study On The ANAMMOX Process System For The Treatment Of Middle-late Landfill Leachate

The middle-late landfill leachate is a kind of complex and difficult-to-treat wastewater,which contains high concentration of ammonia nitrogen and some biodegradable organics.The treatment with physics-chemistry method or traditional biological method has the disadvantages of high operating cost and unstable treatment effect.At present,the emerging ANAMMOX process has the characteristics of high denitrification rate and need no organic matter,and is particularly suitable for the treatment of old leachate with high ammonia and low carbon.In the treatment of middle-late landfill leachate,due to the high concentration of biodegradable organic compounds,there is a certain challenge to the autotrophic ANAMMOX process system.Currently,such wastewater is usually decarbonized first and then denitrified.It is complicated and there is a problem that the concentration of nitrate in the effluent is high.In this paper,the wastewater is treated with a combination process based on ANAMMOX.By gradually increasing the proportion of landfill leachate in the influent,an integrated PN-ANAMMOX reactor with reflux is started.A pilot study was conducted on the start-up of the reactor,the construction of the process system,and the optimization and control of operating parameters,and on the basis of summarizing the experience and conclusions of the pilot test,the control of FA,FNA,and DO was performed on the pilot-scale integrated PN-ANAMMOX reactor.The conclusions are as follows:?1?By gradually replacing the ammonia nitrogen in the simulated wastewater with ammonia nitrogen in the leachate in a lab scale test,the ANAMMOX process system can be successfully started,the start-up time is much longer,and better denitrification efficiency can be obtained with the diluted leachate is directly used as the influent water.Increasing the proportion of leachate can start the ANAMMOX process system faster,but the system's denitrification efficiency is lower than the former.?2?Biodegradable organics will apply an negative impacts on the non-pretreated PN-ANAMMOX process in the situation of that influent ammonia concentration of 600mg·L^-1,ammonia nitrogen provided by landfill leachate is 70%,and biodegradable organics concentration of 170 mg·L^-1,C_BOD/N_TN ratio of 0.3.The pre-UASB reactor can effectively remove the biodegradable organics in landfill leachate and quickly reduce the inhibition of organics to the PN-ANAMMOX reactor.Therefore,it is necessary to put up the UASB anaerobic reactor before the PN-ANAMMOX process when dealing with the middle-late landfill leachate.?3?In the pre-UASB-PN-ANAMMOX process with reflux,DO and FA in the PN zone are controlled at 0.12 to 0.14 mg·L^-1 and 0.5 to 10.2 mg·L^-1,respectively,to achieve stable nitrosation.When influent ammonia nitrogen and COD concentration is1450 mg·L^-1 and 1500 mg·L^-1 respectively,and the HRT is 0.82d.The average effluent TN is 13 mg·L^-1.The NRR of the combined process can reach to 1.75 kg·m^-3·d^-1.The average NRE is 98.58%and COD removal is 99.36%.The combined process achieved the removal of nitrates produced by ANAMMOX.The combined process can treat middle-late landfill leachate deeply and with the stable efficiency.?4?In a pilot-scale PN-ANAMMOX reactor,nitrosation can be initiated under the quality of the raw landfill leachate by adopting a long HRT?7d?and low NLR(0.25kg·m^-3·d^-1)strategy.When HRT is short,the concentration of ammonia nitrogen and FA in the PN zone will quickly rise to a higher level,which is not conducive to the growth of AOB.At medium temperature?19²9??with pH of 8.0±0.1,ammonia concentration of 1800 mg·L^-1.COD concentration was about 2100 mg·L^-1 and HRT was 7d,the nitrite accumulation rate in PN zone was 100%and NPR was 0.18 kg·m^-3·d^-1.The conversion rate of ammonia nitrogen is 72%.NOB activity can be effectively inhibited by combined control of high FA(1³0 mg·L^-1),high FNA(0.02⁰.2 mg·L^-1),and low DO(0.5 mg·L^-1),to achieve enrichment of AOB.?5?By reducing the concentration of influent landfill leachate and reducing the amount of aeration in the PN zone,a suitable NO₂^--N/NH₄⁺-N ratio for anaerobic ammonia oxidation reaction is obtained.It can rapidly start the pilot-scale PN-ANAMMOX integrated reactor after injecting 600L sludge with a concentration of7.3g·L^-1,which with certain ANAMMOX capacity.When the HRT is 1.44d,the overall NRR of the reactor can reach 0.1 kg·m^-3·d^-1.NRE is about 50%.