| This project starts from inducing nitrogen and controlling the eutrophication in drinking reservoir.According to the characteristics of sediment pollution and anoxic condition at the bottom of reservoir in summer and autumn seasons,aerobic conditions in reservoirs must be kept hypolimnetic oxygenation in order to effectively control pollutants released from sediments.Therefore,aerobic denitrification becomes a new scientific subject to remove endogenous nitrogen pollution in aquatic ecosystems.With Zhoucun Reservoir-a typical seasonally stratified reservoir for example,we carried on the research by high-throughput sequencing,Biolog-ECO,quantitative PCR,EEM,in-situ enclosure and laboratory simulation.The objectives of this study were:(1)The spatial and temporal distributions of denitrification rate and community in Zhoucun Reservoir;(2)Isolation,identification,and nitrogen removal characteristics of oligotrophic aerobic denitrifiers;(3)Nitrogen removal characteristics of indigenous aerobic denitrifiers via in situ oxygen enhancement in enclosure experiment ecosystem;(4)Nitrogen removal characteristics of indigenous aerobic denitrifiers via in situ oxygen enhancement using water lifting and aeration system in Zhoucun Reservoir;(5)Technology application research for aerobic denitrification bacteria.The main conclusions are showed in the following:(1)Based on the analysis of field water parameters investigation,denitrification rate and denitrification community,Zhoucun Reservoir occurred obviously aerobic denitrification in the early stage of the thermal stratification.The increase of temperature and the small molecular weight of DOC contributed to aerobic denitrification in reservoir.Meanwhile,the aerobic denitrification bacteria,denitrification functional genes and denitrification rate all increased.The denitrification rate and denitrification community exhibited significant spatial and temporal distributions in Zhoucun Reservoir.RDA showed that nitrogen,TP,temperature,DO and TOC were the critical factors for the distributions of denitrification community.(2)The oligotrophic aerobic denitrifiers were obtained,based on modified enrichment,domestication,screening processes,and morphological-physiological-phylogenetic analysis.The aerobic denitrifica were identified as Acinetobacter,Novosphingobium,Aquabacterium,Sphingomonas,Zoogloea and Delftia.The denitrification characteristics of isolated strain were determined under different culturing conditions,including nitrogen source,carbon source,temperature,C/N,inoculums dosage(v/v)and pH.Meanwhile,we used a series of domestication and source-water experiments to show the feasibility of using aerobic denitrifying bacteria to bioremediate micro-polluted source water.(3)Based on the in situ enclosure experiment,the nitrogen removal characteristics and metabolic activity of the microflora were explored.The results showed that the nitrogen removed effectively.The densities of aerobic denitrifiers and denitrification functional genes increased;Hydrogenophaga,Acinetobacter,Zoogloea and Sphingomonadaceae all had obvious increase,whic were involved in nitrogen cycling.The enhanced indigenous oligotrophic aerobic denitrifiers remained high nitrogen removal ability in enhanced system,the total nitrogn of water system decreased from 2.27 to 1.4 mg/L,and the total nitrogen of sediment system decreased from 4040.24 to 2095.30 ?g/g.The bivariate analysis indicated that gaseous N significantly correlated with the nirS(R2=0.6097)and nirK(R2=0.6989)genes in the enhanced system.The microbial metabolism activity and the diversity index in the enhanced system were higher than those of the control system.These results suggest that it was feasible for nitrogen removal via in situ enhancement using indigenous aerobic denitrifiers for micro-polluted reservoir system.(4)The mechanism,influence factors and nitrogen removal performances were explored through the operation of the water-lifting and aeration system in Zhoucun Reservoir.The hypolimnion anoxic layer abosolutely disappeared and the whole reservoir mixed after the water-lifting and aeration system operated about 35 days,which supplied a suitable environment for the nitrogen removal.The operating of the system enhanced the activity of water microbial metabolic and the capacity of self purification,thus enhancing the indigenous oligotrophic aerobic denitrification bacteria to achieve nitrogen removal.The TN concentration decreased from 2.55 to 0.48mg/L with 81.18% removal rate,and the TN removal rate reached 83.51% compared with the non-operation year;the ammonia concentration decreased from 2.39mg/L to 0.15mg/L with 93.72% removal rate,and the ammonia removal rate reached 91.98% compared with the non-operation year.Meanwhile,aerobic denitrification bacteria increased from 2.56×10~3 to 1.63×10~8 cfu/m L and increased 10~4 times compared with the non-operation year.The denitrification rate had an obvious increase which were higher 10~~20 times than that of the non-operation year.Furthermore,the enhanced system showed a clear inhibition of P,Fe,Mn,TOC,and S performances,which could meet the requirements of class 3,based on the Chinese Surface Water Environmental Quality Standard(GB3838-2002).The operation of the water-lifting and aeration system led the reservoir to be mixed in advance.Thus,good water quality could also be maintained after the system stopped running.(5)Based on the water quality characteristics of drinking water reservoir,we adjusted the strategies for the enrichment and the agent prepared of effective aerobic denitrifiers.The agents remained highly active and exhibited perfect nitrogen removal performance in source water systems.In detail,the TN concentration decreased from 1.83 to 0.38mg/L with 79.4% removal rate,and the numbers of aerobic denitrification bacteria increased from 2.51×10~4 to 6.81×10~6 cfu/m L,obviously. |
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