Study On Three-stage Lateral-cycle Biofilm Process For Nitrogen Removal

With the development of industry and economy, pollution caused by ammonia wastewater has been becoming more and more serious. In recent years, various biofilm processes for ammonia wastewater treatment are consantly emerging. Although those processes have many advantages both in treatment facilities and treatment effect, it was proved that they need a further improvement. In the experiment, three-stage bio-contact oxidation was employed for ammonia wastewater treatment based on anoxic/oxic(A/O) process, meanwhile, according to the circulation flow mode of mixture, So the whole process was know as three-stage lateral-cycle biofilm process for nitrogen removal.Treatment of ammonia wastewater by this process was studied under different influent loads.The experiment was carried out under five different loads totally, C/N ratio of 5:1 was only used in the first stage and the rest stages use C/N ratio of 10:1. The experiment was operated under five different HRTs:3h,6h,12h,24h and 12h. During the experiment, the backflow recycled from anaerobic zone to aerobic zone equaled to the influent flow. During each operation with its load, the removal of COD, NH4+-N and TN had been monitored continuously, trying to find the volume load under which the best removal efficiency of each pollutant could be obtained. The results showed that higher removal efficiency of each pollutant was achieved when C/N ratio is 10:1, HRT is 24h and mixed liquor recycle ratio is 1.During the operation period, the COD and NH4+-N concentrations of the influent were 86-812mg/L and 27.85～89.39mg/L respectively. The experiment results showed that after the system kept stable, COD removal efficiency could remain highly and steadily with average efficiency of 93.14% and the highest efficiency of 96.16% though the influent COD concentration fluctuated to some extent. The average removal efficiencies of NH4+-N and TN were 82.09% and 80.49% respectively and the highest efficiencies of them were 87.86% and 86.64% respectively.The study indicated that when three-stage lateral-cycle biofilm process for nitrogen removal was employed, a optimal removal efficiency could be achieved by reasonable control of several key factors such as DO and the influent volume load.There will be a bright prospect for three-stage lateral-cycle biofilm process for nitrogen removal. Much attention should be paid to it.