Study On Whole Process Analysis And Optimal Operation Of Wastewater Treatment Plant

With comprehensive coverage of the sewage pipe network,the amount of sewage collection has gradually increased,and the country has paid more attention to the water environment.At the same time,the effluent index and the treated water volume of the sewage treatment plant have been continuously improved.Achieving efficient and stable operation of wastewater treatment plants while reducing operating costs has become the primary goal of contemporary wastewater treatment plant design and transformation.The traditional sewage treatment plant transformation model is often based on the experience of the designer,which is random,takes a long time,consumes a lot of money,and cannot predict the risks that it may face in the future.The whole process analysis can put forward the key points of optimization and transformation more pertinently,and reduce redundant testing and blind transformation;at the same time,the mathematical model of sewage treatment,as an emerging tool,can simulate the operation of sewage plants,and solve the current situation in a more time-saving and labor-saving way.This method can also effectively prevent future risks.In this paper,combined with the whole process analysis and mathematical model simulation,BioWin software is used to analyse the current situation of LianHe sewage treatment plant and build a model.Through this analysis,the model determined the best operating conditions and the plant’s optimized operation and transformation plan to meet the new requirements for water output.Through the investigation and analysis of the historical water quality and quantity of the sewage water plant,it is found that the sewage plant influent load is about 70%,and it shows a steadily increasing trend.The sewage plant influent has too many suspended particles,insufficient carbon source,and general biodegradability,which is the main reason for the exceeding of various indicators of the effluent.The effluent COD,SS,NH3-N,and TP all have a certain risk of exceeding the standard.Although TN meets the effluent index,there is still a potential for decline that has not been stimulated.In order to further understand the treatment effect of each process unit of the sewage plant,sampling is carried out in each functional area.The analysis results of the whole process show that the control of DO during the anaerobic section of the wastewater treatment plant is average and it failed to create a good anaerobic environment.Moreover,the phosphorus-accumulating bacteria in the activated sludge are not abundant,and the biological phosphorus removal alone cannot meet the phosphorus removal rate.It needs to be combined with chemical phosphorus removal.In addition,due to the insufficient available carbon source in the influent,the phosphorusaccumulating bacteria have poor phosphorus release effects.The denitrifying bacteria in the anoxic tank has a high activity.If sufficient carbon source is provided,the denitrification can be performed well.The dissolved oxygen in the aerobic tank is not controlled well,and the sludge activity is not good.This leads to a lower rate of sludge nitrification,and COD and ammonia nitrogen cannot be effectively removed.Based on the above analysis,determining the aerobic tank DO,internal and external reflux ratio,the dosage of carbon source,the dosage of phosphorus removal agent,and the removal of COD by powder activated carbon are the key points of this optimization modification plan.The activated sludge model of the wastewater treatment plant was constructed using BioWin software through the collection of the parameters and process parameters of the various structures of the wastewater treatment plant.Through reference to literature and relevant experience values,combined with some simple experiments,the influent sewage components of the model are determined and the initial simulation of the model is carried out.But the simulation result has a large error.The model is calibrated by using sensitivity analysis and the model parameters are adjusted.The adjusted model has a higher degree of fit.The relative error of steady-state simulation is less than 10%,and the error of dynamic simulation is less than 20%,which can be used for scenario analysis.The corrected model is used to simulate the proposed optimization key points and determine the best operating conditions of the wastewater treatment plant by using multiple factor analysis.When the DO of the aerobic tank is 2.50 mg/L,the internal reflux ratio is 200%,the external reflux ratio is 80%,and adding 5600～6400L/d sodium acetate solution in front of the hypoxic pool as the carbon source agent,40mg/L PAC as a chemical dephosphorization agent,it is the best operating condition.At the same time,the engineering transformation plan of the sewage plant is proposed.The powder activated carbon dosing device is added to ensure that the effluent COD meets the standard.The mechanical filter is repaired to ensure the removal rate of SS.Manual dosing is replaced by automatic automatic dosing device,which predicts the dosing amount in advance and is flexible to ensure the removal of TP.The carbon source dosing device is added to provide the amount of carbon source required for nitrogen and phosphorus removal in the sewage plant.The investment of the entire optimization and transformation plan is about 3.56 million yuan,and the new operating cost is about 0.58 yuan/ton.After the optimization of the operation plan and the completion of the engineering transformation,through continuous monitoring of the effluent quality of the sewage plant,it is found that the effluent of the sewage plant can now stably meet the new requirements of the special emission limit in Suzhou.The removal rate of effluent COD,BOD5,SS,NH3-N,TN and TP can reach 90.5%,94.9%,96.0%,94.6%,83.5%and 92.3%.The research content and research methods of this thesis can provide certain guidance and reference significance for the same type of wastewater treatment plants that need to be optimized.