| With the rapid progress of urbanization in China,water consumption was increased gradually,water pollution problems become more serious.In recent years,residents' daily living water,industrial and agricultural production are constantly generating and discharging sewage waste water,causing serious water pollution problems.China's southern urban sewage generally has the feature of low-carbon with high nitrogen and phosphorus.Due to low concentrations of COD is difficult to meet the nitrogen and phosphorus removal requirements of carbon sources,which resulted in many sewage treatment plants nitrogen and phosphorus emissions are not up to standard.The inflow of Heyuan Chengnan Domestic Wastewater Treatment Plant belongs to the typical low C / N sewage.In order to mention the standard,the sewage treatment plant had completed renovation project,which expected the effluent index from the original urban sewage discharge level B standard?GB18918-2002?to the surface water class III Water quality standards?GB3838-2002?.Further limit the nitrogen and phosphorus emissions in wastewater.In order to meet the requirements of discharge standards,Heyuan Chengnan Domestic Wastewater Treatment Plant was added phosphorus pharmacy?PAC?into secondary sedimentation tank to deal with low-carbon source of sewage in the current,which will inevitably lead to high operating costs of sewage plants,excess sludge production,sludge treatment difficulties and other issues.Therefore,this paper has studied a kind of treatment method which can save the running cost of sewage plant and achieve good synchronous nitrogen and phosphorus removal effect.By simulating the actual process,the A/O biofilm reactor was designed and processed,and the ferrous ions were added to the reactor to strengthen the low-carbon source wastewater.The optimum dosage and the strengthening effect of the ferrous ions were explored mechanism.The experimental results are as follows:?1?Different concentrations of ferrous ions were added to the A/O biofilm reactor.When the concentration of ferrous ions is 3mg·L-1,the removal efficiency of each pollutant is the best.The removal rates of COD,ammonia nitrogen,total nitrogen and total phosphorus were 94%,89%,58% and 67% respectively.Among them,COD and ammonia nitrogen in effluent can meet the class ? standard of "Surface Water Environmental Quality Standard"?GB 3838-2002?,and the total effluent nitrogen is superior to the Grade 1A standard of Urban Sewage Treatment Plant Pollutant Discharge Standard?GB18918-2002?,effluent total phosphorus can reach Grade 1A standard of Urban Sewage Treatment Plant Pollutant Discharge Standard?GB18918-2002?.From the macroscopic point of view,the presence of small amounts of ferrous ions in the bioreactor can promote biological reactions.?2?A total of nine pesticides were detected in the influent water of the reactor.Atrazine,Diethyltoluamide,Metolachlor,Ethoxyquin,Pirimicarb,Isoproturon,Metalaxyl,Prometryn,Tebuconazole.With the effect of ferrous ion,A/O biofilm reactor on the above-mentioned several pesticides can promote different degrees of removal.?3?From the point of view of the change of extracellular polymer content on the biofilm,the mechanism of ferrous ion strengthening treatment of low carbon source wastewater was studied.It was shown that ferrous ions could enhance the activity of microorganisms and promote the activity of enzymes in the organism,so that the secretion of extracellular polymer increased.Among them,the increasing of protein and polysaccharide is the largest in the composition.The effect of ferrous ions on protein content is mainly through the change of the isoelectric point of amino acids,thus promoting the protein production.Since the presence of ferrous ions promotes the activity of the enzyme,the production of polysaccharides is also controlled by the enzyme activity,and the carboxyl functional groups in the polysaccharide can directly bind to the ferrous ions in the water,so that the addition of ferrous ions also causes the polysaccharide Increased secretion.?4?After the addition of ferrous ions,the hypoxia and aerobic zone of the biofilm were significantly thickened,and a lot of metazoans can be seen on the biofilm.Protozoa,bacteria micelles and rotifers,nematodes and other micro-metazoan animals were be found by using the electron microscopy,which indicating the biofilm are growing well in a trace of iron environment.?5?The addition of ferrous ions has no effect on the chroma of the effluent from the reactor.The total iron concentration in the effluent is about 0.4mg·L-1,which is in accordance with the class ? of surface water environmental quality standard requirements. |
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