A Biofilm Mathematical Model Of Biological Aerated Filters (BAF)

Biological aerated filters (BAF) was widely used in the secondary treatment or thethorough treatment of wastewater, The key of this process is biofilm which adhered onmediums. Studies about growth, mass transfer and chemical reaction kinetics of biofilmare bases to know and understand BAF reactor’s operational mechanisms and treatmenteffects. Mathematical model as an important way of scientific researches andengineering designs has the characteristic that invests slightly, effects fast,quantifications easily, operability well and so on. Based on theoretical analysis ofbiofilm, the paper had been written of models establishment, forecast by models andaccuracy analysis of models.It took activated sludges of a effluent treatment plant at Chongqing then culturedand acclimated at laboratory, got aerobic bacteria with the help of enriching microbes.Set up BAF disposal system platform, made aerobic bacteria form biofilm on mediumswhich are porcelain granules. After biofilm formation success, continuously feeding andsynchronously measuring and recording data of two sets of COD and ammonianconcentration in outflow. Plotted curves at last.Came into use Monod equation to study and characterize the growth of biofilm,used the Fick law to analyze mass transfer combined with mass balance. Got functionexpression about substrate consumption, concentration distribution and mass transferflux in biofilm by counting. Determined boundary conditions of BAF reactor.Based to the model of ASM2, to combine with correlation parameter of reactor,simplified and established mathematical model which contains13components (used ‘i’to express) and11sub procedures (used ‘i’ to express). ASM2is an classical model atstudying biofilm react, it adequately consider phosphorus removal and denitrification(mainly nitrating and denitrification). The study doesn’t involve phosphorus removal, soreasonably simplified models. To strengthen discussed of nitrating and denitrificationreact process, amended that chemical reaction kinetics parameters To link withreference literature, at the same time, preset dynamical parameters and part of reactingcoefficient which models need to work.Made use of computer to compile program simulated BAF reactor, did datacomparisons, relevance analysis and erroneous analysis between simulated values andmeasured values by SPSS. The simulation effect, on the whole, of COD and ammonian were well, the reliability was better. Its simulation results and the measured valuesbasically tallies, simulated concentrations of outflow had great correlate to actualmeasurement concentrations of outflow and inflow; The scatter graphs ofactual-simulation concentrations of outflow basically center on y=x; the average errorswere about10%between actual and simulation data. It discussed improvements ofmodels, too.In this paper, obtained data by experiments, analyzed and explained basementtheory of biofilm and ASMs ideas. Based on ASM2, simplified and establishedmathematical models. It did well in simulating BAF reactors that the reliability wasbetter from testing by mathematical measure. The study offered well ideas and valuableconsultation to engineering design, operation simulation and other practical applicationsof BAF. The paper had given suggestions, improvements and questions needed furtherresearch of BAF, too.