Study On Biofilm Process Regulation And Microbial Community Composition Of Electroplating Wastewater

As a typical refractory organic wastewater,Electroplating wastewater has large discharge,strong toxicity,refractory degradation,and great harm to the environment.How to realize the environmental protection,high efficiency and low cost treatment of electroplating organic wastewater has become a research hotspot.At present,the treatment methods of electroplating wastewater mainly include chemical methods such as chemical coagulation,ozone oxidation,and Fenton oxidation,and physical methods such as electrolysis and membrane technology,and biological methods.Biological method has obvious advantages in electroplating organic wastewater treatment due to its characteristics of less energy consumption,simple process equipment,low cost,and no secondary pollution.In view of the problems that the existing traditional biological treatment methods are difficult to effectively treat the refractory organic matter,the excess sludge yield is large,and the sludge is easy to bulk up,this thesis proposes the application of the biofilm-AAO process to treat the refractory electroplating organic wastewater.When the biologically active filler is put into the traditional AAO biochemical tank,the microorganisms exist in a suspended state and an attached state at the same time,the biomass is greatly increased,the sludge load rate is greatly reduced,the impact load resistance is improved,and the sludge volume is reduced.Filamentous bacteria are adsorbed on the surface due to the capture of the carrier to avoid sludge bulking.The activated sludge composite biofilm process can give full play to its respective advantages,complement the defects,and improve the stability and processing capacity as a whole.The biofilm is cultivated on the surface of the filler and adapted to the electroplating organic wastewater to achieve the purpose of efficient degradation.The main research contents of this thesis are as follows:(1)The mud film composite process was proposed to treat electroplating wastewater,the small-scale experiment analyzed the organic matter degradation and denitrification and phosphorus removal laws of the biofilm-AAO process,and preliminarily verified the feasibility of treating electroplating wastewater.During the experiment,the AAO-biofilm coupling system has a good film hanging effect,and can effectively treat the refractory organic wastewater of electroplating.After the 22 nd day,the change of COD in the water quality is basically flat,and the COD removal rate is stable at about 89%.The COD removal in the early stage is mainly anaerobic.unit(45.70±14.85%);the latter is mainly anoxic unit(40.59%±14.11%);the biofilm system in the aerobic stage can maintain a stable removal ratio(14.96%±6.57)%,which plays an important role in refractory organic wastewater.The effect of stabilizing the effluent quality.The system was successfully started up after 35 days,and the main way of denitrification was denitrification in the anoxic tank.The denitrification rate of the system reached 70-80% after 60 days of operation.The phosphorus removal effect tends to be stable after 50 days of operation,the effluent concentration is lower than 1 mg/L,and the removal rate is greater than 65%.The phosphorus removal mainly relies on the processes of anaerobic phosphorus release and aerobic phosphorus absorption.(2)The process parameter optimization experiment was carried out,and a four-factor three-level experiment was used to design a parameter optimization scheme based on Design expert 10.0 software.The model building among key parameters such as carrier filling ratio,hydraulic retention time,reflux ratio of nitrifying solution,dissolved oxygen concentration and organic matter dissociation rate was studied.Finally,through parameter optimization,the filling ratio was 33%,the reaction concentration was 2.8 mg/L,the time was 17 h,and the reflux ratio was 230%.Under these optimal conditions,the COD removal rate of electroplating organic wastewater was 92.5%.(3)Analysis of microbial community diversity.From the ? diversity analysis,it could be seen that the microorganisms in the early stage of film formation basically come from the activated sludge adsorbed on the filler,and have a high species richness.In the middle stage of film formation,the species richness increased significantly,and the microorganisms were in a state of rapid growth.In the later stage,the microbial abundance decreased and the microbial diversity increased,and the microbial community of the biofilm system became more diverse.Proteobacteria,Bacteroidetes,Nitrospirae(nitrifying bacteria),Acidobacteria and Chloroflexi were dominant in the biofilm of electroplating wastewater influent,The dominant genera at the genus level are Nitrosospira,Zoogloea,Haliangium and Sphaerotilus.Comparing the biofilm samples and sludge samples,the number of microorganisms in the biofilm biofilm is more and the species richness is higher than that of the activated sludge in the same period.(4)The Analysis of the actual operation of wastewater treatment in electroplating enterprises by biofilm-AAO process.The experimental results show that the average concentration of COD in the effluent in the later stage of the system is 28.030mg/L,and the average removal rate is 92.62%;the average concentration of ammonia nitrogen is 0.45mg/L,and the average removal rate is 98.82%;the average concentration of total nitrogen is5.09mg/L,and the average removal rate is 98.82%.The rate is 91.22%.The average total phosphorus concentration is 0.27mg/L,and the average removal rate is 90.88%;the effluent quality can basically reach the treatment effect of pretreatment plus biochemical method,and this process has practical value for refractory electroplating organic wastewater.