Application Of Immobilized Microorganism Technology On Ammonia Nitrogen Removal In DTRO Treated Landfill Leachate

Disk tubular reverse osmosis(DTRO)membrane technology introduced abroad is an advanced method used in landfill leachate treatment.During initial operation,the treatment process is stable with high effluent quality.However,with reaction time increasing,the membrane of DTRO would be blocked due to the corrosion effect of the leachate,and the load of the pressure pump would increase,then the DTRO would be working in very low efficiency which will lead to higher concentration of ammonia nitrogen in the discharge than the standard.Therefore,immobilized microorganism technology was studied in our research for ammonia nitrogen degradation in landfill leachate treated by DTRO.Firstly,the characterization of carrier was analyzed,activated and domesticated.Then,the influence of Hydraulic Retention Time(HRT),Dissolved Oxygen(DO),temperature and Carbon/Nitrogen(C/N)on ammonia nitrogen removal by immobilized microorganism was investigated,and the optimal operation conditions was obtained based on the analysis.According to the results above,the denitrification pathway was carried out,and the related kinetics was set up in order to understand the relationship between the concentration of ammonia nitrogen,total nitrogen and HRT.Finally,the diversity of denitrification bacteria in the reaction system was monitored by high-throughput sequencing technology to investigate the denitrification mechanism,which provided the theoretical basis for practical application of immobilized microorganism on ammonia nitrogen treatment in DTRO treated landfill leachate.The immobilized microbial carriers were characterized by scanning electron microscopy,specific surface area and porosity analyzer and Fourier transform infrared spectroscopy.The characterization result of immobilized microorganism carrier showed that it is made of an inorganic materials containing silica or silicate,with large specific surface area,the internal structure is long cylindrical hole,and the surface structure is rough,loose and porous layered,which is in favor of the multiplication of the bacteria.It was showed in the reseach that the activation of the carrier is fast,the domestication takes short time and effluent quality is improved.In the end of domestication,there are a large amount of microbial populations found in the system,including Rotifera,Epistylis sp,oligochaetes and so on.Immobilized microorganisms were used to treat the simulated leachate DTRO effluent,the influence of HRT,DO,temperature and C/N on the removal of ammonia nitrogen by immobilized microorganisim were investigated.It is indicated from the results that the optimal conditions for HRT,DO and temperature are 5d,4.0mg/L and 25?30?,respectively.In this conditions,the concentrations of ammonia nitrogen and COD in the effluent are 13.0?20.0 mg/L and 6.8?14.4 mg/L respectively without any additional carbon source.However,the concentration of TN does not meet the discharge standard in the Landfill Pollution Control Standards(GB16889-2008)in China.It is obtained from the research that the removal rate of TN is increasing with the increase of C/N.Therefore,additional carbon resources is necessary in the treatment process in order to to decrease the concentration of TN.Immobilized microorganism technology was applied on the practical ammonia nitrogen treatment in DTRO treated landfill leachate.It is obtained from the results that the influence of HRT and DO on denitrification is similar to that conditions in simulated experiment,and the removal rate is higher in the process of practical landfill leachate treatment.It is known from the denitrification pathway that nitrification and denitrification reaction happens at the same time,and the process transformed from shortcut nitrification/denitrification to complete nitrification/denitrification with the increase of HRT.The kinetics of denitrification in the reactor was also carried out,and the obtained kinetics equation of nitrification and denitrification are:?f(??)=1-e-(0.2056?+0.0135)(R2=0.98417)??f(TN)=1-e-(0.05790-0.0295)(R2=0.97153),respectively.High-throughput sequencing technology was employed to identify microbial communities in the reactor in the optimum operating condition.The results showed that there are 18 kinds of bacteriophytas in the system,including five dominant phylums:Proteobacteria,Bacteroidetes,Actinobacteria,Firmicutes and Nitrospirae.Except bacteroidetes,others(49.3%)have contribution to denitrification.It is obtained from the results that there are 64 kinds of bacterias at the genus classification level,with dominant genus including Sediminibacterium,Novosphingobium,Hydrogenophaga and Aeromonas.It is showed in the representative sequences of Operational Taxonomic Units(OTUs)that there are variety of denitrification bacteria species in the reactor,such as nitrobacteria,denitrifying bacteria,heterotrophic nitrification-aerobic denitrification bacteria and denitrification bacteria with nitrogen fixation function(such as Azospirillum and Rhizobium).Therefore,it can be concluded that the nitrogen removal process includes autotrophic nitrifying,heterotrophic nitrifying,heterotrophic facultative anaerobic denitrification,nitrification/denitrification reaction,and shortcut nitrification/denitrification reaction,which indicated that immobilized microorganism technology can remove the ammonia nitrogen in DTRO treated landfill leachate independently.