Study On Process Simulation And Design Optimization For Municipal Wastewater Treatment Plants

Economic development and rapid urbanization bring forward a higher request of wastewater treatment.The more strict effluent criteriarequests the optimization of design and operation in wastewater treatment plants(WWTPs).Assisted by modeling and simulation, we could evaluate treatment processes within the design stage to optimize the design and operative parameters.This study provides a full flow of process simulation and design optimization for municipal WWTPs based on BioWIN® software, including model set up, data collection and reconciliation, calibration and validation, etc. Different research approach is provided for new plant, plant in service, plant to be upgraded.Model of Anaerobic-Anoxic-Oxic(A2/O) process of Zhenjiang East WWTP(new plant) was built andsimulation results indicate that: the design process can meet the effluent criteria in normal state; additional carbon or changing part of aerobic tank to anoxic tank can avoid effluent TN exceeding when influent COD is low; effluent COD cannot reach the criteria when the influent containmore than 30% of industrial waste water; more SRT or more area of aeration is needed in winter to make sure the effluent ammonia reach the criteria if the activity of AOB is weak.Model of Orbal oxidation ditch process of Wuxi Chengbei WWTP(plant in service) was built and simulation results indicate that: effluent TN can reach the minimum when the internal recycle ratio is controlled in the range of 10% to 20%; the sludge recycle ratio and displacement of sludge are in good condition; Adding carbon resource before the inlets can get a best effect; the PAC for phosphorus removal is over added, the appropriate dosage is 1800 kg/d; using more rational aeration disc combination can improve effluent quality or save energy.Model of suspended carrier process of Shenyang Shenshuiwan WWTP(plant to be upgraded) was built and simulation results indicate that: the current process has problems of low MLSS in tank and lack of anoxic area; the optimization of operative parameters cannot reach the new criteria so that the updating is necessary; the updated process can improve effluent qualityobviously and meet the requirement;the actual biofilm culturing of suspended carrier need to be assured otherwise effluent ammoniaconcentration will increase; One point of effluent is better than two point of that; Enhance the SRT can ensure the effluent meet the criteria in chilly weather.