| The existing sewage biological treatment process is becoming more and more complex,accompanied by high energy consumption and high carbon emissions,and exhibits endogenous drawbacks in resource recycling and energy recovery.Under the requirements of low-carbon green,sustainable development and ecological civilization construction,it is particularly important to develop a new sewage treatment model that conforms to the current development concept.For example,short-range treatment technologies(such as physical and chemical processes)are used to replace traditional biological methods,and resources are recycled while realizing sewage treatment.For this reason,this study constructed a set of urban sewage treatment technology based entirely on physical and chemical treatment technology,which is based on coagulation,membrane separation and electrochemical technology.Firstly,the orthogonal test of coagulation hydraulic conditions is used to determine the optimal hydraulic conditions for coagulation.Secondly,under the optimal hydraulic conditions,three coagulants of PACl,ferric chloride and aluminum sulfate are compared for the removal of COD under different dosages.Effect,analyzed the sludge particle size analysis of the corresponding coagulation flocs,and comprehensively screened out the appropriate coagulant.In addition,the effluent of different processes is monitored by conventional indicators,and the feasibility of physical and chemical methods for urban sewage treatment is explored.At the same time,high performance liquid chromatography and three-dimensional fluorescence spectroscopy are combined to analyze the enrichment characteristics of different pollutants in each process.Discuss the ability and stability of the process in the treatment of domestic sewage,and explore its advantages and potential in resource recovery.Below are key research findings:(1)Through the orthogonal test of hydraulic conditions,it is determined that the stirring speed is the main factor affecting the coagulation hydraulic conditions,followed by the stirring time.The best hydraulic conditions are: rapid stirring(320r/min)0.5min,medium speed stirring(160r/min)7min,stirring slowly(80r/min)for 8min.the optimal dosage of PACl is 120mg/L,and the optimal dosage is The average particle size of the formed sludge is 52.33μm higher than other coagulants.Through comprehensive comparison of organic matter removal rate and particle size distribution changes,the paper selected PACl as the main coagulant used in the experiment among the three coagulants of PACl,ferric chloride and aluminum sulfate.(2)The average removal rate of COD,TN,NH4+-N and TP in urban sewage by coagulation-membrane filtration was 90.77%,36.65%,39.67%,98.0%,and SS was all removed.Regarding the excess NH4+-N in the effluent,the subsequent 160 min of electrochemical oxidation can be basically completely removed,while the TN is stabilized below 10mg/L,and the overall process effluent can stably reach the first-level A standard.(3)Synchronous coagulation membrane filtration can effectively slow down membrane fouling,increase membrane flux and improve effluent water quality.In the synchronous coagulation membrane filtration and coagulation adsorption membrane filtration modes,the effluent COD concentration was further reduced by 26.17% and30.38% compared with the distributed coagulation sedimentation filtration.The PACl-based coagulation-ultrafiltration membrane concentration process passed a455 min concentration cycle,and the COD concentration was concentrated to1609.2mg/L.(4)Coagulation sedimentation can effectively enrich the biopolymers with relative molecular mass greater than 100,000 Da in the urban sewage DOM and reduce the pollution of subsequent membrane filtration.The molecular weight of the residual DOM in the coagulation effluent is concentrated in 800 Da,450Da and 150 Da.Nanofiltration and ultrafiltration cannot be particularly effectively removed.It needs to be combined with electrochemical treatment. |
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