A Biofilm Multiple-Substrate Model (BMSM) And Its Application To Biological Aerated Filters

Biological aerated fileters(BAF) can combine ammonla,carbonaceous matter,and solids removal in a single-unit process.In this paper,we studied the process of an BAF reactor,and etablished a biofilm multiple-substrate model(BMSM) at the base of the theory of biofilm convection and reaction.Also an one--dimension BAF reactor model wos presented on the ground of the concept of phase uniform biofilm.A computer program was developed to modele and simulate the steady operation of BAF with a Matlab's tool.Aimed to model multiple substrate removal in biofilm,some simplifications had been implemented at the base of the activate sludge model NO3(ASM3).Biofilm multiple-substrate model(BMSM) was established through combining the simplified ASM3 and the theory of convection and recation. With SMSM as it's basic function,an one-dimension BAF reactor model was developed on the ground of the concept of phase uniform biofilm.Model function showed that the capability of substrat removal depends on the area of biofilm,and has no relation with the volumel of reactor.Filled with lignt granular ceramics,a designed BAF consists of carbon oxidized stage and denitrified stage.Filter was fed with synthetic wastewater. Many of coefficients and parameter, including removal efficiency, biofilm density, thickness, area were measured.A computer program was developed for analyzing the sensitivity of the principal effluent targets, including COD, TN, NH4+-N and NO3-N,to kinetic parameters and biofim parameters.Sensitivity of the targets are low to most kinetic parameters,but high to biofilm parameters such as biofilm density,thickness,area.Accoding to sensitivity analysis,some model parameters were adjusted.A satisfied agreement between the modeling values and practical measurement values was obtained.The result showed that the model is effective in the range of the test condition.The reactor's steady operation was modeled by BMSM and COD, TN, NH4+-N and NO3-N Concentration profile relating to the height of BAF was studied.The biofilm multiple-substrate model(BMSM) could finly model the steay operation of BAF,and provide some valuable reference date for the designation and management of BAF. And it is worthy of carrying out a further research.