Establishment And Experimental Optimization Of Cost Model For HCA And Its Compound Coagulation/Biological Contact Oxidation Process

At present,Rural domestic sewage treatment process in China is still relatively scarce,and the development of high efficiency and low energy consumption treatment proces s is still the hot spot of rural sewage treatment.HCA as a polymer organic coagulant can effect ively remove pollutants of raw water in sewage treatment.A lot of research has been carried out in the field of water treatment.Coagulation pretreatment with HCA can effectively remove pollutants of sewage and reduce the subsequent biochemical treatment load.It is a simple and effective pretreatment process.Biological contact oxidation process is a biochemical process suitable for rural domesticsewage treatment,which has the advantages of small area,Available indoors andsimple operation.This project adopts HCA and its compound coagulant coagulation/biological contact oxidation combined process to treat domestic sewage,optimizes the parameters of the combined process by establishing a minimum operating cost model,and minimizes the operating cost under the premise of ensuring the treatment effect,and achieve the goal of economic and efficient treatment.The model optimization results were verified by experiments and provided guidance for subsequent practical applications.By analyzing the operating cost components of the combined process,the minimum operating cost model of the combined process is established by analyzing and calculating the main component cost of the pharmaceutical cost and energy consumption cost,and the experimental research content is determined according to the model,which provides the establishment of the later model,deas and basis.In order to simplify model,through static test,the effects of coagulation stirring speed,coagulation stirring time,PAC-HCA compounding and coagulant dosage on the effect of HCA and its compound coagulant on domestic sewage are investigated.The SS,TP,and COD removal rates are analyzed.The test results show that when the initial pH value and the coagulation stirring speed are constant,the optimal operating parameters are coagulation stirring speed of 200r/min,stirring time of 20min,and PAC-HCA compounding ratio of 15:1.The removal effect of PAC-HCA compounding coagulant on pollutants is better than that of HCA alone.Through the establishment of a test device,the start-up and treatment efficiency of the combined process were studied,which provided a reference and basis for the model establish-ment.When the COD removal rate is above 70%and the ammonia nitrogen removal rate is a bove 60%,the biological contact oxidation pond accomplishes the start-up.A/O biological contact oxidation reactor can treat the domestic sewage effluent COD,NH4+-N,SS concentration to meet the first-class A standard,but the TN and TP removal effects are general,especially the phosphorus removal effect is poor.Selected The PAC-HCA dosage(1mL/L,2mL/L,4mL/L),gas-water ratio(10:1,12:1,15:1,18:1),HRT(13.3h,15.6h,18.2h)to compare the pollutant removal efficiency.The optimum operation parameters of the combined process were:PAC-HCA dosage 1mL/L,gas-water ratio 12:1,HRT 18.2h.Under the optimum conditions,the removal rates of COD,NH 4+-N,TN,TP and SS were 99.16%,99.99.16%,respectively.59.52%,75.78%and 99.03%.The removal efficiency of TP by combined process is better than that by single biological contact oxidation process.and Coagulation treatment can effectively reduce the energy consumption of biochemical pool and improve the treatment effect of pollutants.Based on relevant experimental data and research results,The function relations of chemical cost and aeration energy cost are expressed respectively with COD concentration in and out of water as independent variables.Finally,the minimum operating cost Cmin is taken as the dependent variable,and the coagulation effluent COD concentration S1 as the independent variable to establish the minimum operating cost model under different sewage discharge standards.When the Standardsfor Irrigation Water Quality(GB5084-2005)is used as the water quality index of combined process effluent,the minimum operating cost model is obtained as follows(?)When the first level A criteria specified in the Discharge Standard of Pollutants for Municipal Sewage Treatment Plant(GB18918-2002)is used as the water quality index of combined process effluent,the minimum operating cost model is obtained as follows(?)The simulation results show that At higher inlet concentration the operation cost of combined process is lower than that of single biological contact oxidation process when the effluent reaches different effluent indexes.PAC-HCA coagulation pretreatment increases the cost of reagents,but greatly reduces the cost of aeration energy consumption of biochemical ponds,and the overall operation cost is lower.Taking the first-class A discharge standard as the effluent index,the combined minimum operating costis calculated according to the average influent water quality during the experiment.The results show that when the influent concentration of COD,TN and TP are 300 mg/L,50 mg/L and 6 mg/L respectively,the operation cost of the combined process is 0.027 yuan/m3 less than that of the single biological contact oxidation process.The corresponding dosage of PAC-HCA is 0.96mL/L,and the gas-water ratio is 12.5:1.The comparison with the experimental results shows that the model calculation results are basically consistent with the actual situation,But there's some error.When the PAC-HCA dosage is 1 mL/L and the gas-water ratio is 12:1,the removal efficiency of COD and NH4+-N by the combined process reaches the first-class A standard.It is feasible to optimize the parameters of the combined process by using the minimum operating cost model.