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

The feasibility of the novel fixed bioreactor anaerobic-anoxic-aerobic-aerobic system for treatment of coke plant wastewater has been tested at pilot-scale in this paper. Firstly, anaerobic-reactor was applied to improve the capability of biological oxidation, then through denitrification in anoxic-reactor and oxidation in first aerobic-reactor and nitrification in second aerobic-reactor COD_cr and NH₃-N were removed.Anoxic-reactor has been studied during biofilm culturing phase and test-run phase in coke-plant wastewater treatment process. The combination of naturally culturing and artificially culturing with seeding proved to be highly effective while the system influent temperature was about30°C and 3-6mm light granular ceramics as carrier of anoxic-reactor. It took 40d to complete biofilm culturing, 80% and 70% removal efficiencies of COD and NH3-N were achieved respectively in bioreactor system during biofilm culturing phase. It was very necessary to avoid high ammonia influent during biofilm culturing phase for it has been proved to be strongly inhibitory to microbe activity.HRT of anoxic-reactor was 12h during test-run phase, and recirculation ratio changed in the range 1-3. The largestNO3-N load was 0.359 kg/(m3 ? d), and when NO3-N loadwas about 0.1 kg/(m3 ? d) ,reduced ratio of NO3-N was largerand the largest one was 98.1%. At recirculation 3 average NO3-N reduced ratio was the largest about 70%, and along with the rate of COD/ NO3-N increased the reduce ratio of NO3-N increased too, lack of carbon is one important influence factor to coke plant wastwater treatment.The proportion of COD removal capacity in anoxic reactor to total COD removal capacity in bioreactor system decreased when recirculation ratio rose from 1 to 3, it was 42% while recirculation ratio was 1, which decreased to 12.7% at recirculation ratio 2 and 5.6% at 3.In test-run phase, Bioreactor system effluent COD and NH3-N concentrations had attained primary and secondarynational standard about wastewater discharge ?GB8978-1996? respectively.