Performance Comparison And Reconstruction Pilot Study Of The Activated Sludge Process In Wastewater Treatment Plant Process

The wastewater treatment plant we studied is a comprehensive sewage treatment plant which primarily treats the printing and dyeing wastewater from the large-scale textile industry.The construction of the plant process is divided into three periods.The first phase of plant was completed and operated in June 2001 formally,the second phase of plant was put into use at the end of 2003,and the sewage treatment capacity was preliminary designed for 300000 tons of wastewater each day.Along with the development of the industrial park to expand,sewage water increasing,the water quality worse and worse,and treatment technique of backwardness and treatment facilities aging,it had all resulted that the operation condition can not reach the desired effect.To achieve the requirements of the latest emission standards,the reconstruction of the wastewater treatment plant is imperative.For rational reconstruction of the treatment plant,in combination with treatment plant,the first phase and the third phase of biochemical treatment effect were analyzed on the basis of previous experimental data,and the existing problems of the first phase was discussed.Based on the comparison of different processes,the anoxic-aerobic activated sludge process was chosen to replace the original traditional activated sludge process,and the new process was verified in the pilot scale.Compared with the original process and the pilot tests,it was found that the process of pretreatment + two aeration combination(AB process),had a better performance in the CODcr level of effluent than the aerobic process of the first phase,the CODcr level of the former was decreased by 15%-30% than the latter.In the view of engineering application of the first phase,the AB process would have more advantages such as easy reconstruction and low investment and operation cost.According to the water quality of the effluent from the second phase of treatment plant,the parameters optimization was studied,and we tried to adjust the range of some important parameters in the biochemical treatment period such as dissolved oxygen,sludge concentration,reflux ratio,to improve the treatment effect.Through the test of laboratory experiment it was found that the best combination of dissolved oxygen,sludge concentration,reflux ratio was as follows: 3.5 g/L,2.5 mg/L ~ 3.5 mg/L and 65%.Then,and the parameters was used in the actual processing system,to achieve standard upgrades of the second phase of treatment plant.The reconstruction of the wastewater treatment plant has important practical significance,it would provide better theoretical and practical reference for the transformation of the large sewage treatment plant optimization,and would play an exemplary role in the sewage disposal industry,at the same time would has long-term significance to the water protection and urban development in this area.