| With the continuous deepening of the concept of sustainable development,sewage treatment and resource recycling have attracted widespread attention.In recent years,with the rapid economic development and rapid population growth,the discharge of industrial wastewater and domestic sewage has increased significantly.Among them,high-salt wastewater and low-carbon source wastewater have developed into two difficult problems that cannot be ignored.In recent years,due to environmental friendliness and economic effects,sequencing batch reactor(SBR)for wastewater treatment has attracted more and more attention.As one of the main methods of biological wastewater treatment,the SBR method has the advantages of small footprint,flexible and simple operation,and strong tolerance.It has been widely used in the treatment of various water bodies.However,the composition of the water body is complex,and it is easy to adversely affect the SBR system,and the response mechanism of microorganisms is still unclear.In view of the above problems,this study takes the SBR system as the research object,systematically explores the performance of different factors(low nutrition,high salt and surfactant)on the nitrogen and phosphorus removal of the SBR system and clarifies the response mechanism of microorganisms.The main content and results are as follows:Part 1 selected glucose as a single carbon source to investigate the effect of different gradients of influent carbon concentration on the nitrogen and phosphorus removal performance of the SBR system,and at the same time studied the effects of activated sludge enzyme activity,protein,polysaccharide and nucleic acid on the molecular level.The results show that in the SBR system,the reduction of carbon source concentration will inhibit the nitrogen and phosphorus removal performance of the activated sludge in the system.The aerobic stage is beneficial to increase the dehydrogenase activity,but the decrease of carbon concentration will inhibit the dehydrogenase activity;when the carbon concentration of the influent is 40% of the initial influent concentration(COD=153.24 mg/L,nitrogen source=20 mg/L),the SBR can still operate stably and maintain good nitrogen and phosphorus removal performance.However,when the carbon source concentration is less than 40%,its nitrogen and phosphorus removal performance is significantly inhibited,and the solid suspended solids content increases.The content of extracellular polymer is obviously increased,leading to the threat of the stability of the microorganism itself,and the microbial flora in the system is impacted.When the influent carbon concentration is60%,the protein content in the extracellular polymer is the highest,but the polysaccharide content is the lowest,and the removal of pollutants still maintains good performance.(Corresponding to Chapter 2 in the article)Based on the research in Part 1,the SBR system can optimize the limit of the influent carbon concentration(40%)that can maintain the biological activity.Part 2investigates in depth the effects of salt concentration on nitrogen and phosphorus removal performance,enzyme activity,and EPS in the SBR system.The results show that under low carbon source conditions,when the salinity is less than 10 g/L,the efficiency of nitrogen and phosphorus removal in the SBR system increases with increasing salt concentration,and the effect of salt concentration on nitrogen removal is more significant.When the salinity increased to 5 g/L,the overall enzyme activity in the system was inhibited,and when the salt concentration was further increased to10 g/L,the enzyme activity increased slightly.In addition,as the salt concentration increases,the polysaccharide content increases and part of the protein in the EPS is converted into carbon source and energy,thereby participating in the growth and metabolism of microbial cells.Moreover,as the salt concentration increases,the flocculation and settling of activated sludge weakens.(Corresponding to Chapter 3 in the article)The above Parts 1 and 2 have examined the effect of high salt and low carbon source conditions on the nitrogen and phosphorus removal performance of the SBR system.Given that urban sewage and some industrial wastewater are not limited to high salt and low carbon sources,the components are usually compared.Among them,anionic surfactants,as a type of commonly used industrial and household cleaning products,are widely present in various water bodies,and thus may have an adverse effect on the SBR operating system.Part 3 studies the effect of anionic surfactants(SDS and SDBS)on the nitrogen and phosphorus removal performance of the SBR system under high salt conditions.Studies have shown that the addition of SDS and SDBS to the SBR system can suppress the removal of nitrogen and phosphorus,and the inhibitory effect of SDS is more significant.In the system with SDBS,the sludge activity is hardly affected,while in the system with SDS,the sludge activity is increased.In addition,the addition of SDS and SDBS reduced the content of EPS in the system.The content of TB-EPS in the system containing SDBS hardly changed,while the content of TB-EPS in the system containing SDS decreased significantly.(Corresponding to Chapter 4 in the article)Part 4 used 16 S rRNA sequencing method to deeply explore the changes of microbial community structure and composition response under high salt and surfactant stress.The results show that in the presence of high salt and surfactant,Proteus is the main population.In addition,the removal performance of the SBR system is not only affected by the dominant population,but also by the microbial community richness and community diversity.Therefore,the reduction of nitrogen and phosphorus removal performance of activated sludge is the result of a combination of factors.(Corresponding to Chapter 5 in the article)... |
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