Pilot-Scale Study on Combined Biological Filter for High Nitrogen and Low Carbon Wastewater Treatment

With the development of discharge and reuse standard of industrial wastewater,requirements of denitrification are becoming more and more strict, which leads researchto focus on the denitrification process of high nitrogen and low carbon wastewater inthe field of industrial wastewater treatment particularly. This study was based on recentdomestic and international research progress, taking Combined Biological Filter （CBF）as the core process, discussed the performance of CBF as secondary biochemicaltreatment for salt chemical wastewater and as advanced treatment for coal chemicalwastewater, respectively, completed kinetic analysis and summarized the problemsoccurred during designing and operation of CBF process.On one hand, a hydrolysis acidification reactor and two-stage of CBF wasused in the treatment of salt chemical industrial wastewater. The start-up of theprocess succeeded after29days. Operating parameters were as follows:hydraulic loading rate of0.37-0.74m/h （not including backflow）, recirculationratio of100%and gas-water ratio of3:1. In terms of water quality, the averageconcentration and the removal efficiencies of COD, NH₃-N, TN and SS were78mg/L （60%）,1.05mg/L （93.4%）,18.9mg/L （63.8%） and4.9mg/L （94.5%）,respectively, which met secondary biochemical treatment requirements of saltchemical industrial wastewater. This process was of higher resistance to loading,and the increasing of the hydraulic loading rate （0.37-0.74m/h） benefited theremoval of pollutants. Based on the recording of the pollutant concentrationalong the process, removals of COD, NH₃-N, TN and the SS were discussed inhydrolysis acidification area, first-stage anoxic/aerobic area and second-stageanoxic/aerobic area. On the other hand, the one-stage of CBF was applied in thetreatment of fertilizer wastewater. The start-up took35days. Operatingparameters were as follows: hydraulic loading rate of0.32-1.49m/h, C/N of4:1.In terms of water quality, the average concentration and the removal efficienciesof COD, TN, turbidity and conductivity were42.5mg/L （20.3%）,65.1mg/L（56.6%）,7.8NTU （59.2%） and2651μs/cm （20.2%）, respectively, which metreuse standard of industrial recycling cooling water after being treated through electro-adsorption subsequently. This study also derived and calculated thekinetic model and corresponding constant respectively regarding organicsremoval, nitration reaction and denitrification reaction of CBF. Besides, thecharacteristic of integration was deeply summarized for CBF process. Problemsduring designing and operaion of CBF, such as pretreatment, selection of media,water/air distribution system and backwashing system, were analyzed in detail,and improvement recommendations were given point for point as well.