Preliminary Study On Modeling Of Percolation In Particle Media Biological Trickling Filter

Biofilter is a priority applied technology to choose in rural decentralized wastewater treatment engineering application because of its characteristics such as simple operation and maintenance management, low processing cost, less quantity of sludge and so on. With the use of small packing particles, particle media biological trickling filter has advantages of steady seepage flow of liquid and large amount of biomass interception. It also can use other artificial reinforcement method to improve the treatment effect and efficiency, which makes it a new direction of biological filter technology. Preliminary study of permeability characteristics and mathematical model was developed around the core problem of biofilter clogging.Same grading of silica sand media and humified media were filled into reactors. The existence and rationality of two-period model was verified. Within the scope of known period I, different concentrations of simulated water was supplied. Systematically study was taken on the relationship between the changes of permeability coefficient and porosity. Result showed that during the period I of percolation model before demarcation point, permeability coefficient is determined by the change of porosity. During the period II of percolation model after demarcation point, permeability coefficient basically stably decline slowly as porosity continued to decline and there came to obvious clogging phenomenon. Using mathematical fitting method to get the function relationship between the change of porosity and permeability coefficient:the percolation model of silica sand is K/K0=0.0023e6.1917(Φ/Φ0),R2is0.9707and the percolation model of humified media is K/K=0.0118e4.2955(Φ/Φ0),R2is0.9407. Relationship between the change of porosity and microbial growth apparent kinetics was studied. Hydraulic partition was obtained with different height of the piezometric head, which indirectly reflected the distribution of biomass in different height of media. With biomass conveniently and effectively determined, microbial apparent yield coefficient was calculated. Through the determination of MLVSS, surface area of media and contaminant removal, detach coefficient was calculated. Then the theoretical model of porosity variation and microbial apparent kinetic parameters was obtained. Correction coefficient of the model was determined according to experimental data. The model describes the relationship among the change of porosity, the amount of substrate degradation, the reaction time and early pore volume during I period of reaction under the condition of three kinds of water concentration. I period percolation mathematical model of hydraulic permeability variation and attached growth microbial apparent kinetic parameters of silica sand biofilter and humified media biofilter was constructed by combining empirical model and theory model. A series of experimental data verified this model and proved that the calculated results coincided to the experimental data, indicating that the first phase of the research objectives was completed.