| The release of endogenous nitrogen in the sediment is also an important pollution source for water when the exogenous nitrogen is gradually controlled.Continuous aeration is the main way of water restoration,and continuous aeration realized nitrification of ammonia nitrogen.However,denitrification has been ignored,and the concentrations of the total nitrogen and nitrate nitrogen remain high.The overlying water and sediment in Shiwuli River were collected.Intermittent aeration was used to realize the release of endogenous nitrogen and efficient short nitrification and denitrification.Molecular ecology method was used to analyze microbial community composition and functional microbes during short nitrification during intermittent aeration.In addition,the main environmental factors affecting microbial community and function gene abundance of nitrogen transformation were also analyzed.Moreover,rapid analysis of nitrogen concentration was realized in intermittent aeration by near infrared spectroscopy.The release and transformation of nitrogen in polluted rivers were researched by intermittent aeration.The results of intermittent aeration showed that the ammonia nitrogen concentration decreased and nitrite concentration increased gradually during the aeration stage of overlying water,and the shortcut nitrification occurred obviously in the aeration stage of overlying water.The ammonia nitrogen increased gradually owing to the sediment release when aeration was stopped.However,nitrite nitrogen gradually decreased owing to shortcut denitrification,and obvious shortcut denitrification was realized.During intermittent aeration,the change of nitrate nitrogen is stable with the concentration of 0?0.38 mg/L,and the concentration of the total nitrogen decreased gradually.The shortcut nitrification and denitrification of the overlying water was effectively achieved by repeated intermittent aeration.The microbial community structure and microbial diversity in intermittent aeration process were studied by molecular biology.The main environmental factors affecting microbial community and diversity were analyzed by redundancy analysis and variation decomposition method.The microbial community structure of overlying water showed that Comamonas has important contributes to shortcut nitrification during shortcut nitrification stage.The short denitrifying bacteria in the overlying water have little contributions to denitrification in the process of shortcut denitrification.Redundancy analysis indicated that DO,pH and FA were important influence factor to the microbial community structure during the short cut nitrification stage,and DO,pH,FA and ammonior nitrogen were the major factors affecting the microbial community structure during shortcut denitrification stage.However,during short cut nitrification stage,DO and pH were important influence factor to the microbial community structure in the sedimentment,and pH and NO2-were the major factors affecting the microbial community structure during shortcut denitrification stage.The analysis of microbial diversity in sediment indicated that the nitrification functional bacteria may exist at the phylum level during short cut nitrification stage,however,no obvious shortcut nitrification functional bacteria were found at the level of the class and genus.During short denitrification,the Thauera genus in sediment is the main force to achieve short denitrification in rivers.The results of redundancy analysis revealed that nitrogen,ammonior nitrogen and pH had key effect on the microbial diversity distribution during shortcut nitrification and shortcut denitrification stage.The PCR fluorescence quantitative method was used to study the response of nitrogen conversion gene to intermittent aeration.Redundancy analysis were used to analyze the main environmental factors affecting the functional genes.Pearson correlation analysis was used to reveal the correlation between the functional gene of the nitrogen conversion and the chemical index of sediment.PCR fluorescence quantitative analysis indicated that the amoA showed a significant increasing trend during shortcut nitrification stage,showing a significant shortcut nitrification function.The change of nxr was not significant,indicating that less convertion between nitrite nitrogen and nitrate nitrogen.During shortcut denitrification stage,the nirK and nirS showed an obvious increasing trend,and cnorB also showed a significant increasing trend,indicating that the significant convertion between nitrite nitrogen and nitric oxide,and nitric oxide and nitrous oxide.The Pearson correlation analysis,between sediment basic chemical indexes and nitrogen transformation function genes,showed that nitrite nitrogen has significant correlation with nxr functional genes during shortcut nitrification stage(Pearson correlation:r=0.924).Moreover,there is a significant correlation between DO and Archaeal-amoA,Bacterial-amoA,and nirS(Pearson correlation:r=0.909;r=0.934;r=-0.917).Ammonior nitrogen,nitrite nitrogen,nitrate nitrogen,total nitrogen,C:N and TOC have significant correlations with nitrogen conversion genes during shortcut denitrification stage.The analysis of redundancy and variance decomposition analysis showed that DO,NH4+-N and C:N were the main factor affecting the transformation of functional genes during shortcut nitrification stage.DO,NO2--N and TOC in the shortcut denitrification stage were the main factors affecting the transformation of functional genes in sediment.The timely detection of nitrogen is the key to control the intermittent aeration process.Near infrared spectroscopy combined with mathematical statistics method(synergy interval partial least squares,interval partial least squares,BP neural network and support the establishment)was used to establish quantitative analysis model of the total nitrogen,ammonia nitrogen and nitrite nitrogen.The method of near infrared spectroscopy combined with mathematical statistics overcomes the traditional chemical detection method of time-consuming,consumption of drugs and second pollution.The results show that the rapid quantitative analysis models can analyze the concentrations of the total nitrogen,ammonia nitrogen and nitrite nitrogen.The quantitative analysis model of nitrogen index established by siPLS method is the most accurate.The quantitative analysis model of support vector machine is the second accurate model.BP neural network quantitative analysis model is similar as the quantitative analysis model of iPLS,and support vector machine quantitative analysis model is slightly worse.The shortcut biological denitrification of overlying water was studied by intermittent aeration of polluted rivers in this paper.The characteristics of microbial community and the response to environment have been carried out using molecular biology.The abundances of nitrogen functional genes and environmental factors were further studied.The rapid characterization of nitrogen index was realized by the method of near infrared spectroscopy combined with mathematical statistics.The transformation mechanism of nitrogen in polluted rivers was further enriched during shortcut biological denitrification,and a novel detection technology for the polluted rivers was provided. |
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