Impact Of Nanoparticle On Nitrogen And Phosphorus Removal Efficiency Of SBR System And Mechanism Research

With the rapid development of nanotechnology and the gradual expansion of the application of nano materials,different kinds of nano particles can not avoid entering the water environment.As the transfer hub of water environment,the sewage treatment system is responsible for the centralized treatment of a variety of wastewater functions,and in the process of receiving wastewater,nanoparticles will also enter the sewage treatment system.In order to systematically explore the impact of nanoparticles on the sewage treatment system,this paper constructs an SBR reactor in the laboratory to treat three common nanoparticles(Ag NPs?ZnONPs?MWCNTs)in sewage as the object,to study the influence of different kinds,different concentrations and different action time of nanoparticles on the sewage treatment efficiency and microbial flora of SBR system,analyze the influence rule of different nanoparticles on the nitrogen and phosphorus removal efficiency of sewage treatment system,explore the mechanism of different nanoparticles affecting sewage treatment system,and predict the Na The harm degree of rice particles to the sewage treatment plant was found out,and the limitation value of SBR system to nano particles was found.The nitrogen and phosphorus removal efficiency and mechanism of different nano particles were analyzed and compared,which provided theoretical support for the normal operation of the sewage treatment plant.In order to explore the effect of nanoparticles on nitrogen and phosphorus removal efficiency of SBR system,three kinds of common nanoparticles(Ag NPs,ZnONPs,MWCNTs)were compared and analyzed under different concentrations(0.5 mg/L,2.5 mg/L,10 mg/L)of short-term exposure(30 min sampling interval within 6 hours)and long-term exposure(Under the condition of 12 hours sampling interval within 60 days),the concentration trend of nitrogen and phosphorus in the effluent of SBR System in the laboratory.The results are as follows:(1)After short-term exposure(6 h)of nanoparticles,the system has no effect on the removal of nitrogen and phosphorus indicators.The removal rates of ammonia nitrogen and soluble phosphate by the system exposed to nanoparticles are over 95% and 90%,respectively.The concentration difference between nitrite nitrogen and nitrate nitrogen and the blank group is about 0.1 mg/L-0.5 mg/L.(2)After long-term exposure(60 days),the exposure of 0.5 mg/L nanoparticles had no effect on the efficiency of nitrogen and phosphorus removal of the system;the system exposed to 2.5 mg/L nanoparticles began to reduce the efficiency of ammonia nitrogen and soluble orthophosphate(SOP)after 30-35 days of nanoparticles exposure,which was lower than the blank control group by 3.98% and 8.3% on average,The concentration of nitrite in the system was 0.33 mg/L higher and 1.16 mg/L lower than that in the blank group.This phenomenon was more obvious in the system exposed to 10 mg/L nanoparticles.The average treatment efficiency of ammonia nitrogen and SOP was lower than the original 8.8% and 20.96%,the effluent nitrite was 1.13 mg/L and the effluent nitrate was 2.2 mg/L.In order to further explore the mechanism of nano particles affecting nitrogen and phosphorus removal in SBR system,in the long-term exposure of nano particles(20 days is a period of time),the system sludge biomass(MLVSS/MLSS),sludge sedimentation ratio(SV),extracellular polymer(EPS)and lactate dehydrogenase(LDH)were monitored.After 60 days of long-term exposure,the respiratory inhibition rate,surface morphology and microbial flora of the system sludge were analyzed.The results are as follows:(1)Under the long-term exposure of 0.5 mg/L nanoparticles,the exposure system has no effect on the activated sludge morphology and microbial flora.The differences of the indicators of the activated sludge in the system are in a small range compared with the blank group.The surface morphology of the sludge is good,and the abundance of functional microbial flora is stable.(2)Under the long-term exposure of 2.5 mg/L nanoparticles,each index of sludge in the system began to decrease with the increase of action time.Among them,MLVSS/MLSS decreased by 11.87% on average,SV increased by 5.83% on average,and protein and polysaccharide content decreased by 7.68 and 6.07 mg/g on average.In the sludge system,the surface morphology of some cells began to break,and the microbial diversity began to decrease.The abundance of nitrospirae decreased by 1.3-1.47%,and that of ?-Proteobacteria decreased by 1.14-2.38%.The decrease of the abundance of functional bacteria indicated that the water treatment efficiency of the system began to change.(3)Under the long-term exposure of 10 mg/L nanoparticles,the indicators of sludge in the system deteriorated obviously.The difference of sludge biomass and sedimentation in the blank group reached 22.7% and 17.23% at one time,reaching the critical value in the early stage of sludge bulking.The content of extracellular polymer in the system decreased with the increase of action time,and the content of protein and polysaccharide decreased by 19.17 mg/g and 15.4 mg/g on average.In terms of microbial community,the abundance of nitrospirae decreased by 2.55% and that of ?-Proteobacteria decreased by 4.19%.The decrease of sludge activity and the abundance of functional bacteria results in the deterioration of nitrogen and phosphorus removal efficiency.The experimental results show that when the exposure concentration of nanoparticles is more than 2.5 mg/L,the denitrification and phosphorus removal efficiency and sludge activity of the sewage treatment system will be inhibited,and the effect will increase with the extension of exposure time,which will have adverse effects on the surface morphology and microbial flora of sludge.The experimental results and mechanism of sludge system activity index provide certain data support for the limited exposure concentration of nanoparticles in sewage treatment system,and provide theoretical support for the safe operation of sewage treatment plant.