The Effect Of Wastewater Treatment Plant Effluents On Microbial Community In Receiving Water

In recent years,with the acceleration of urbanization and the continuous growth of urban population,the demand for daily chemical products is also increasing,which leads to the increasing load of wastewater treatment plants.Therefore,more and more pollutants can not be treated by sewage treatment plants and enter the received water,leading to a series of water health problems.At present,the water quality evaluation of wastewater treatment plant effluent mainly relies on the existing physical and chemical indicators to carry out qualitative or to study the ecological effects of a certain kind of pollutants on a few aquatic animals and plants in the water body.The existing evaluation methods can not fully reflect the ecological impact of wastewater treatment plant effluent on water body.In this paper,biofilms and planktonic microbial communities in different receiving rivers were selected as observation objects.DNA samples were analyzed by high-throughput sequencing technology.The effects of sewage treatment plant effluent on receiving waters were studied by studying the composition and distribution of microbial communities in water.By measuring the routine physical and chemical properties of the receiving water,it is found that TN,TP and COD_cr in the wastewater treatment plant effluent are higher than those in the upstream of the receiving water,which indicates that the wastewater treatment plant effluent will increase the risk of eutrophication of the receiving water,thus affecting the ecological function of the receiving water.The pH value at the outlet is lower than that at the upstream of the water body,which is due to the treatment process of the wastewater treatment plant.The concentration of TN and NO₃^--N in the receiving water varies seasonally,and the higher the water temperature,the lower the concentration.We have studied the biofilm and planktonic microbial community by analysis of similarities in the receiving water body and found that the community structure of the biofilm is significantly different from the planktonic microorganism?R>0.716,P=0.001?.Cyanophyta is the dominant phylum in biofilm and Proteobacteria is the dominant phylum in planktonic microbial community.This is due to the adhesion of bacteria,such as cyanobacteria,which have a better adhesion,so they occupy a dominant position in the biofilm community.At the same time,we found that the planktonic microbial community in water body is very sensitive to the change of water body.Therefore,the instantaneous change of water body can be indicated by observing the composition of planktonic microbial community,while the biofilm community can be used to indicate the long-term change of water body because of its complex composition.We further analyzed the biological information of microbial community and physical and chemical index data in receiving water by RDA,and found that there were significant seasonal differences?R>0.435?and spatial differences?R>0.511?in microbial community in receiving water.The seasonal differences were mainly caused by temperature.Among them,TN,NO₃^--N and other indicators also caused seasonal differences in microbial community in water.While the spatial differences is mainly due to the change of physical and chemical properties of upstream and downstream water caused by sewage treatment plant effluent,such as pH,TP.By analyzing the structure of biofilm and planktonic microbial community in the receiving water and the properties of the receiving water,we can reflect the ecological effects of wastewater treatment plant effluent on the water body comprehensively,at the same time,we find that the environmental factors play important roles in the change of microbial community.This study can provide technical support and participation for the comprehensive evaluation of the impact of wastewater treatment plant effluent on the receiving water.