Mathematical Simulation Of Wastewater Treatment By Bioflocculation-regeneration Process

The bio-flocculation regeneration technology which is developed based on the mechanism of organic contamination adsorption by activated sludge can remove organic contamination and suspended solids of domestic wastewater significantly and can reduce the investment of infrastructure and the cost of operation simultaneously. It is important for underdeveloped region wastewater treatment plants (WWTPs) construction. At present, most researches of biological flocculation are focused only on system structure, reactor configuration and influencing factors, such as sludge retention time (SRT), suspended solid concentration. The principle is not yet clear understanding and the research on dynamic is still lack. Thus, it is failed to establish a mathematical model for the process and the results are ununiversal. Through systematic experiments, the biological flocculation process key parameters were optimized and a universal mathematical model was developed in this study.The matrix expression for describing the biological reactions in bioflocculation-regeneration reflects an appropriate modification of ASM1, with a consideration of adsorption process and microbial hydrolysis under aerobic, anoxic, and anaerobic conditions.Meanwhile, using of process kinetic equations and mass balance equations analyze the material changes within the system. Most of the model parameters using the default value of activated sludge model No. 1.In order to determine the key parameters,sensitivity analysis was adopted .The result showed that one is the most sensitive one is heterotrophic yield YH among 7 stoichiometric parameters.At the same time,seven other parameters,μH,k H,K X,Ks,k ads,μA,b A have high sensitivity in 15 kinetic parameters.The parameters,μH,k H,K X,Ks,k ads,μA,b A which have high sensitivity do the parameter estimation according to the sensitivity analysis result. The results of sensitivity analysis providing a viable basis for the selection of parameters for the model.The database used for Model calibration and validation originates from a lab-scale bioflocculation-regeneration system for the treatment of municipal wastewater.The verification results show that the established model was able to simulate and predic the performance of bioflocculation-regeneration process.The last,Mathematical modeling techniques shall be applied for optimize the process operation parameters in the process system. Simulation results show that: When the sludge concentration reaches a certain value, the reflux ratio, oxidation time and SRT have little effect on the organic particle matter(CODSS) removal rate. But they have greater impact on organic matter (COD), dissolved organic matter (SCOD) and NH4+-N removal rate . Flocculation time play an important role on the effluent COD, SCOD,CODSS and NH4+-N removal rate.If the flocculation time is too short, it have a direct impact on the rate of activated sludge to adsorb CODSS and micro-organisms utilize SCOD and NH4+-N. Combination of all factors, optimize the bioflocculation-regeneration process operation parameters and get the ideal operation parameters: reflux ratio is 0.6, the flocculation time is 40min, oxidation time is 1.5h and the sludge age is 6d.