Modeling Study On Upgrading WWTPs And Saving Energy Consumption

According to the 13th Five-Year Plan,most existing WWTPs need to be upgraded.In addition,WWTPs,as the end of the municipal energy consumption,need to meet strict emission standards while saving energy consumption reduction.Traditionally,the optimization and upgrading of wastewater treatment process is always based on engineering and operation experience,with poor efficiency and high cost.International experience shows that as a useful tool,modeling can achieve twice the result with half the effort in the optimization and upgrading of WWTPs.Therefore,this study aims to optimization and saving energy consumption of two existing wastewater treatment processes by modeling,which not only effectively solve the problems,but also demonstrates a very pratical application technology for other domestic wastewater treatment processes.Process models for a CAST process in Hebei and an A~2/O process in Shanxi were established based on TUD model respectively.The operation optimization and simulated upgrading analysis were carried out after calibrating relevant parameters and validation of process models.The simulation shows that the adjustment of the current process has no practical effect on the biological phosphorus removal for the congenital defects of CAST in Hebei,and chemical phosphorus removal is still needed.Comparative upgrading simulations of A~2/O and UCT demonstrate that biological phosphorus removal greatly improved compared with the current process.UCT shows better phosphorus removal and can treat 1.5 times current influent load,and increase the treatment capacity of existing CAST process.It can meet the phosphorus discharge standard of"the first grade A"and save massive phosphorus removal chemicals if the UCT process is selected for the transformation of CAST.Scenario simulation of different temperatures,SRT,internal and external rerurn ratio and carbon source addition of A~2/O process in Shanxi shows that,without much carbon source addition,the effluent has no significant improvement.The adjustment of the current process cannot meet urgent need of saving carbon source consumtion.However,upgrading UCT process can save more than 50%of the phosphorus removal chemicals and much carbon source.The full flow model of A~2/O process in Shanxi was established based on ASDM model,and the sludge sidestream hydrolysis model was constructed to predict effect.The simulation shows that it provides mainstream volatile organic acids(VFAs)at most when sidestream sludge ratio was 5%.However,due to the small proportion of sidestream hydrolysis flow relative to the system volume,the variation of VFAs and phosphorus accumulating bacteria(PAOs)in the system is small,and the effluent cannot be significantly improved.Neither expanding the scale of project nor using possible measures to accelerate hydrolysis can get better result.It’s even worse than improving the anaerobic environment.This shows that the effect of the sludge sidestream hydrolysis upgrading is very limited,and it’s unnecessary to implement in the plant.