Microbiological Process Involved In Formation Of Black And Malodorous Water In Typical Areas

With the acceleration of urbanization in our country,excessive discharge of sewage has caused eutrophication of rivers and gradually led to the black and odor of water.The black-odor water is a serious phenomrnon of water pollution.So it is important to investigate the mechanism of water quality degredation for water pollution prevention and remediation.However,the studies on black-odor water mainly focus on the chemical mechanism of water degredation method.The researches on the microbiological mechanism of black-odor water are obviously insufficient.In this study,we selected sampling rivers in the north and south of China(Ziya river and Dingshan river)to investigate the microbial mechanism of water degredation.Comparative analysis of physical and chemical properties of water,the number of carbon and sulfur cycle functional gene,microbial community composition and diversity,mainly showed the following results:(1)According to the analysis of river water quality indicators(DO,TN,NH4+-N,NO3--N,SO4 2-,COD),Ziya river has higher nutrient and salt load than dingshan river,and its eutrophication is more serious,which is more likely to cause the occurrence of "water bloomn and lead to black-odor water.(2)Carbon cycle related functional microbiological community structure:a.The abundance of mcrA and pmoA in Dingshan river did not change significantly.However,the abundance of mcrA was significantly higher than that of pmoA in Ziya river.b.There are ten OTUs for mcrA genes.In the OTU1,Ziya river accounts for 65.3%of the total.In OTU2,Dingshan river accounts for 80.4%.Seven OTUs for clustering pmoA genes.Its advantages OTU are the following three categories:OTU1,OTU2,OTU3.c.T-RFLP results showed that the mcrA gene in the two rivers had almost no dominant segment.The dominant segments of the Southern river(Dingshan river)are mainly concentrated in 146bp,243bp,and 285bp.In Northern river(Ziya river)177bp is the dominant fragment in its forest regin.In the industrial area,53bp,147bp,and 761bp became the main predominant segments,while the 60bp and 86bp fragments in the agricultura pollution area became dominant communities;the pmoA gene in the two rivers contained a common dominant fragment of 247bp.d.According to the significant level of environmental factors,the major environmental factors affecting the mcrA gene of Dingshan river are DO and pH,and the main environmental factors affecting the Ziya river mcrA gene include total phosphorus(TP)and COD;The main environmental factors affecting the pmoA gene in Dingshan river are SO42-and NH4+-N.There was no factors that can significantly affect pmoA gene.(3)Sulfur cycle functional microbiological community structure:a.The abundance of soxB in both rivers was significantly higher than the abundance of dsrB.b.17 OTUs were obtained for soxB gene.In the OTU1,the Dingshan river accounted for 97%,and in the OTU2,the Dingshan river accounted for 90%,in the OTU3 and OTU4,the Ziya river accounted for 90%;for the pmoA gene clustering,15 OTUs can be obtained,and their advantages OTU are the following three types:OTU1,OTU2 and OTU3.c.T-RFLP results showed that the dominant fragments of the soxB gene in the southern river(Dingshan river)were mainly 38bp and 416bp,and the dominant fragment of the northern river(Ziya river)was mainly 499bp;the dominant community of the dsrB gene in the southern river(Dingshan river)was mainly 380 bp,163 bp,125 bp,and 108 bp,and distributed evenly between upstream and downstream.The dominant segment of the northern river(Ziya river)also contained 163 bp,of which 64 bp fragments differed from the forest and agricultural areas in the industrial area.d.According to the significant level of environmental factors,the main environmental factor affecting soxB gene in Dingshan river is NH4+-N,and the main environmental factors affecting dsrB gene are NH4+-N and pH;In the Ziya river,the major environmental factor affecting the soxB gene is DO,and the major environmental factor affecting the dsrB gene is TP.(4)High-throughput sequencing of microbial 16S rDNA from water samples:a.Under the phylum level,the dominant species of aquatic organisms included Proteobacteria,Firmicutes,Bacteroidetes,Cyanobacteria;In the class level,the dominant communities include Betaproteobacteria,Gammaproteobacteria,Alphaproteobacteria,Cyanobacteria,Clostridium,Bacteroides,Deltaproteobacteria.b.Sobs,Shannon,and Sinpsoneven indices were selected for Alpha diversity analysis.The results indicated that the Ding Shan river in the South river has a rich microbial community and high diversity,and these three indexes have a significant negative correlation with nitrate nitrogen content in the water.There is no correlation with other physical and chemical indicators.c.With considering to heatmap analysis,pH is associated with Microgenomates,Planophyta,and Trichophyton.Omnitrophica,Elusimicrobia,Cloacimonetes and Tenericutes are related to DO.Tenericutes,Fibrobacteres,Lennisphaerae,Hydrogendentes,FCPU426 and Microgenomates are related to sulphate level.CPR2,KSB3_Modulibacteria,Omnitrophica,Acidobacteria,Unclassified_K_norank,Hydrogenedentes and Armatimonadetes are related to nitrate level.Tenericutes,Fibrobacteres,Lentisphaerae,Deferribacteres and Synergistetes are connected to ammonia level.Saccharibacteria was significantly negatively correlated with COD;Omnitrophica and Elusimicrobia were significantly positively correlated with TP.d.CCA analysis of physicochemical properties and bacterial communities showed that D1 was greatly affected by pH,D2 and D3 were greatly affected by total phosphorus,Z1 and Z2 were greatly affected by dissolved oxygen and nitrate nitrogen,and Z3 was affected by ammonia nitrogen.