Study On Experiments And Simulation Of Pollutants Removal And Headloss Development In Denitrifying Biological Aerated Filter

It targeted at exploring the dynamic variation and spatial distribution alongdenitrifying biofilter (DNBF) height of outlet water quality and headloss, as well asthe impact of biomass accumulation on them, with both biofilm mathematical modelsand bench scale experiments.Firstly, based on diffusion-reaction principle, a one-dimensional advective-diffusion-reaction non-steady-state model of DNBF was built, including one-dimensional advective-diffusion–reaction equations and biofilm diffusion-reactionequations. According to the character that nitrogen gas would be generated in DNBF,the Cadle’s porosity model was modified. DNBF pollutants removal model andheadloss model was coupled by the modified porosity model, for the purpose ofanticipating outlet water quality and headloss variation during a complete runningcircle of DNBF.Secondly, an upflow denitrifying biofilter (DNBF) system was setup and itsliquid age distribution curve was measured. Biofilter in this research was proved veryclose to plug flow reactor. Meanwhile the removal performance and headlossdevelopment during a running cycle were investigated and the spatial distribution ofheadloss and pollutants along the filter layer under steady operation was analyz ed.The headloss increasement, removal of NH4+-N, NO3--N, COD and biomassaccumulation were relevant to some degree. The headloss increasement in the DNBFwas mainly caused by the decreasement of partial porosity, resulting from thedevelopment of biofilm and the accumulation of nitrogen gas.Finally, based on MATLAB platform, the simulation of non-steady-statedenitrifying biofilm and headloss model was performed. This program c ould simulatethe treatment of synthetic wastewater under denitrifying conditio ns to some extent,the relative error of model turned out be less than18%. The influence of differentoperating parameters on the treatment effect was studied. Effluent nitrateconcentration increased with the improvement of influent nitrate concentration, whilethe effluent ammonia and COD concentration decreased, and headloss growncorrespondently. Effluent nitrate, ammonia, COD concentration and headloss all wentup with the increasement of hydraulic loading; Effluent nitrate nitrogen, ammonianitrogen and COD concentration decreased with the reduction of media size, while the head loss increased sharply.