The Effect Of Aerobic Moving Bed Biofilm Reactor Process On Landfill Leachate

The leachate from incineration plants has the characteristics of big fluctuation in the amount of water,complex composition,high concentration of organic matters and ammonia nitrogen,high content of refractory,toxic and harmful substances,which has been a major problem in the field of industrial wastewater treatment.At present,the combination process of anaerobic-physicochemical has been widely used to treat landfill leachate in engineerings.Anaerobic process can remove organic matters effectively while the physicochemical process can remove ammonia nitrogen effectively.However,the physicochemical process will increase operating costs and cause secondary pollution.Therefore,it is necessary to develop an efficient biological treatment technology with low energy consumption and cost to achieve the removal of high ammonia nitrogen in the leachate.The objective of this article was to study the effect of aerobic moving bed biofilm reactor(MBBR)on the treatment of landfill leachate from anaerobic effluent.Firstly,the research completed the start of aerobic MBBR and the optimization of operation parameters.And then the effect of influent load on pollutants removal and the removal effect of pollutants as well as the material transformation during the long-term stable operation were studied.At last,the biomass,microbial activity,microbial community and morphology in the reactor were studied.The inoculated sludge of aerobic MBBR was from a aeration tank of the domestic sewage treatment plant.It was trained with artificial simulated sewage,and then acclimated with landfill leachate of low concentration.After the acclimation of sludge,the biofiller was added to the aerobic zone with the volume ratio of 20%,and then the biofilm was formed on the biofiller.When the effluent quality was stable and the removal rate of COD and ammonia nitrogen was 70% and 60% respectively,the biofilm was considered to be stable.After the reactor was started,the performance of biofiller was tested.The results showed that the biofilm had high activity and good effect on the removal of pollutants.The operating conditions of aerobic MBBR were determined after optimizing the operating parameters,and the condition were: HRT= 8d,the ratio of A/O was 1:3,the reflux ratio of nitrification was 300%.Under the optimal conditions,it could achieve a sufficient contact of microorganisms and pollutants and the concentration of COD and ammonia nitrogen in effluent could meet the requirements for the next process.Under the low influent load of COD,the microorganisms were in the starving state.And it would effect the removal rate of COD and ammonia nitrogen,but the effluent quality could meet the requirements.Under the high influent load of COD,the ratio ofC/N incrased,which was helpful for the growth of microbial,the removal rate of COD and ammonia nitrogen was 73% and 95% respectivly.Under different influent load conditions,aerobic MBBR could guarantee the quality of effluent,which had a great significance in engineerings.During the long-term operation,the removal rate of COD and ammonia nitrogen was 67% and 95% respectively.The removal rate of COD fluctuated obviously with the changes of water temperature,while the removal rate of ammonia nitrogen was relatively stable.The changes of water quality were analyzed by TN,fluorescence spectroscopy,gel filtration chromatography and ultraviolet spectroscopy during this period.The results showed that the unsaturated and macromolecule refractory organic matters could be transformed into simple,small molecule matters,reducing the concentration of COD in effluent.Some organic matters which can not be biodegraded,such as humic acid were discharged into the next process with the effluent.The biomass of aerobic MBBR was stable and rich,especially for the microbial attached to the biofiller,which had a high metabolic activity.The micro-environment formed by the biofilm on the biofiller provided a favorable condition for the degradation of various pollutants.The results of microbial community showed that the dominant bacteria in MBBR were Proteobacteria,Bacteroidetes,Firmicutes,Deinococcus-Thermus and Actinobacteria.Most of the dominant bacteria were gram-negative bacterias which were ubiquitous in sewage treatment,and they had the ability to degrade organic matters as well as nitrification and denitrification.Suspended sludge had a lot of space,showing a disorderly state,and the biofilm had the smooth appearance,three-dimensional structure and multiple pores.Microorganisms in the system were predominantly cocci and bacilli.Microorganisms in suspended sludge were not abundant and scattered around,while microorganisms on the biofilm had the regular morphology and abundant biomass.