Startup And Test Run Of Aerobic Reactors In A₁/A₂/O₁/O₂ System For Coke Plant Wastewater Treatment

The aerobic reactor system of combined anaerobic/anoxic/aerobic/aerobic fixed-film bioreactors consisted of a biological contact oxidation reactor and a biological aerated filter(BAF).Oxidation of the organic carbon compounds was carried out in the biological contact oxidation reactor and nitrification was performed in the BAF. The low COD feed load in the BAF favoured nitrification so that high NH₃-N removal efficiency was achieved.A pilot-scale anaerobic-anoxic-aerobic-aerobic fixed biofilm systerm was used for coke plant wastewatertreatment.The aerobic reactors ,the first with plastic balls as carrier and the second with light granular ceramics as carrier, were studied during biofilm culturing and test run period.The experimental results showed the start-up of biofilm culturing was completed in 40d at 30 °C through the combination of naturally culturing and artificially culturing with seeding.The removal efficiencies of COD,NH₃-N were about 80% and 70 % respectively.A thorough study was done to review the influnces on the performance of biofilm culturing in such aspects as temperature, regime, pH, alkalinity, DO ,the influent loading of COD,NH₃-N.During the test run period, the effluent COD in the first aerobic reactor was about 200mg/L with removal efficiency of 80% under conditions of high fluctuation in COD concentration even with the maximum COD loading of 2.79kgCOD/(m3.d).This proved COD removal capacity in the first reactor was high.The experiment was carried out to confirmed high COD loading and high NH₃-N concentration inhibited nitrification and influnced the removal efficiency of NH₃-N in the BAF through the regulation of COD,NH₃-N feed concentration .When COD,NH₃-N influent loading rate were less than 0.67kgCOD/(m3?d),0.49kgNH₃-N/(m3.d)respectively. The removal efficiency of NH3-N was enhanced and the effluent NH3-N concentration was less than 25mg/L,which attained the secondary national standard about wastewater discharge ((GB8978-1996)) .This study showed that it was very important to maintain the specific population in separate reactors,in order to reduce the competition between different bacterial species and to enable the microorgnisms to grow under optimal conditions. The tested treatment configuration is suited for treating coke plant wastewater with the low C/N and high concentration NH3-N.