抄録
The mathematical model of biofiltration which was developed for the treatment of precoagulated sewage from a grid chamber is applied to explain the experimental performance of a biofilter used for tertiary treatment of secondary effluent. Its applicability is discussed by comparing the results simulated using the model with the experimental data. This model can favorably estimate the 525-day treatment performance, biomass concentrations and details of water-quality profiles through the filter bed in continuous treatment without changing any parameters of the proposed model, including rate constants, half-saturation concentrations and yield coefficients. Then some design and operational parameters are discussed referring to this model. Under large fluctuation of nitrate concentration in the filter, McCarty's equation can be used to determine the appropriate amount of methanol to be added. The maximum ammonium nitrogen loading rate in the nitrification filter is shown to be 0.55 kgN·m-3·d-1 in winter. Also, the maximum nitrate nitrogen loading rate in the denitrification part of the polishing filter is shown to be 5 kgN·m-3·d-1 in winter. The developed model is proved to be a promising tool for discussing the design and operational parameters of full plants.
