The Study On Simultaneous Removal Of Iron,Manganese And Ammonia By Biological Filter Coupling Autotrophic Nitrogen Removal

In recent years,with the rapid development of economy,industrial and agricultural in China,groundwater which is known for its relatively stable water quality has also been polluted to varying degrees during the process of recharge.In view of the increasing pollution of ammonia and organic matter in groundwater containing iron and manganese,three simulated biofilters were used to build the technology that adopting biofilter coupling autotrophic nitrogen conversion to simultaneous purification of iron,manganese and ammonia nitrogen in groundwater.The start-up method and operational parameters of the biofilters which simultaneously removed iron,manganese and ammonia from three kinds of water qualities were studied.By combining theoretical calculation with experimental data,the main cause of total nitrogen loss was clarified,and the effects of manganese and ammonia on nitrogen transformation in biofilters were also explored.At the same time,the composition and succession of microbial community in biolfilters were analyzed by molecular biology analysis method.In this study,separated inoculation was adopted as the start-up method of all the three biofilters coupling autotrophic nitrogen conversion.In the biofilter coupling autotrophic nitrogen conversion that simultaneously removed iron,manganese and ammonia?1#?,56 days were needed for the successful start-up and the final filtration rate was 5 m/h.The average quantity of nitrogen loss was 0.69 mg/L and Mn removal capacity was the key factor determing the duration of the start-up period.In the biofilter that simultaneously removes Fe,Mn,ammonia and COD_Mn?2#?,243 days were needed for the successful start-up and the final filtration rate was 4 m/h.The average quantity of nitrogen loss was 0.32 mg/L.The organic matters in the influent increases the difficulty of the daily biofilter operation.Mn,ammonia,nitrite removal capacity and the clogging problem jointly determined the final working condition and the duration of start-up period.In the biofilter that simultaneously removes Fe,Mn,ammonia from low temperature groundwater?3#?,the temperature of raw water was 4.1-4.3^oC.Due to different filtration rate,the temperature of the influent and effluent water presented a gradient cooling phenomenon.333 days were needed for the successful start-up.The average quantity of nitrogen loss was 0.18 mg/L and the water temperature of influent and effluent were 5^oC and 6.5^oC.The effluent nitrite content was the key factor determing the duration of the start-up period.The presence of organic matter and low temperature led to the reduction of total nitrogen loss in the biofilter coupled autotrophic nitrogen removal and the extension of the start-up time.In this study,autotrophic nitrogen conversion process was the most probable reason for the total nitrogen loss in all the three biofilters.The nitrogen conversion was accomplished by complete nitrification and autotrophic nitrogen conversion.In steady operation period,the average autotrophic nitrogen conversion proportion were 48.1%?1#?,15.9%?2#?and 29.5%?3#?,respectively.The changes of environment and working conditions caused by low temperature and organic matters had obvious effects on autotrophic denitrification process.In the biofilters that simultaneously removed Fe,Mn and ammonia,autotrophic nitrogen removal proportion rose slightly with the raise of Mn concentration and declined along with the raise of ammonia.The fluctuation of Mn and ammonia indeed impacted the ammonia conversion regulation in the depth side of the matured filter bed.Mn removal could be assessed by first order reaction in all the eight periods and the k values were more comparable than those in abiotic Mn oxidation.As to the results of microbial community structure analysis,there were obvious differences in the composition and succession of microbial community in biofilter under different working conditions and water quality conditions.In the biofilter that simultaneously removed iron,manganese and ammonia,11 putative MnOB genera were decteced and MnOB was the dominant bacteria in the whole filter bed.The genus Exiguobacterium accounted for the largest proportion in all the five samples.Three AOB genera and three NOB genera were also detected;Candidatus Kuenenia was the only detected AAOB.In biofilter that simultaneously removed Fe,Mn,ammonia and COD_Mn,9 putative MnOB genera were decteced and the proportions of these genera dropped sharply;Candidatus Kuenenia was also the only detected AAOB.In biofilter that simultaneously removed Fe,Mn,ammonia from low temperature groundwater,7putative MnOB genera were decteced and the proportions of these genera also dropped sharply.Nitrosomonas and Nitrospira served respectively as AOB and NOB in the filter layer and Candidatus Brocadia was the only detected AAOB.In the biofilters coupling autotrophic nitrogen conversion,there was no significant positive correlation between the pollutants removal quantity and the distributon of functional microorganisms.Based on the results of molecular biology analysis,the key point of reverse regulation process should be guided by functional bacteria with outstanding adaptability in stable operation period under different working conditions,which can accelerate the maturation and operation stability of biofilter by creating suitable conditions of proliferation and improve the treatment efficiency.