Experimental Research On Low C/N Ratio Municipal Wastewater Treatment By UCT Process

With the improvement of living standard and lifestyle changes, the pollutant's composition and proportion of sewage changes correspondingly. Now, the domestic sewage with low C/N ratio is not uncommon in many cities, and the new standards on wastewater discharge nutrients such as nitrogen and phosphorus control requirements are more and more stringent. In municipal wastewater biological treatment system, how to improve the nitrogen and phosphorus removal efficiency in the low C/N ratio sewage is a difficulty.UCT process is similar to the A2/O process, improved on the base of A2/O process by South Africa Cape Town University. This process further remitted the contradiction between denitrification and phosphorus removal. UCT process is rarely applied in the country. In this paper, UCT process was used to treat high ammonia, low-nitrogen ratio urban wastewater. Test contents including equipment start-up test run, UCT and the A2/O process contrast, the operating parameters optimization, and testing the optimum dosage of throwing and adding of carbon source. Verified the treatment efficiency of UCT Process on low C/N ratio domestic sewage, and provided reference for application.The experimental results showed that:1.With same influent and operation condition, contrast UCT technology and A2/O process , the results showed that UCT process had obvious advantages and better removal rate.2.The average removal rate of COD was as high as 85% in the reactor with a stable stage. UCT system has good nitrification, and nitrogen removal efficiency can be stable up to 95%. Aeration rateand directly affected nitrogen removal effect. Increasing volume of aerobic zone was beneficial to nitrification, but easily lead to the secondary settling tank sludge floating.3.The test water BOD5/TN<2, to the TN removal, UCT process can not achieve the desired results. Before adding carbon resources; TN removal efficiency of the system can be maintained at about 55%. Changing the operating parameters change process on the TN removal rate was increased, but increased marginally,。4.The system had a high removal on TP, which could be stabilized at around 88%without taking into account the case of nitrogen removal. In the case of good nitrification, the efficiency of phosphorus removal was above 50%, and the system run stably.5.after adding carbon sources,the TN removal efficiency of the UCT system can be increased to 80%, raise a big margin in the present stage of experimental carbon and nitrogen ratio imbalance cause the system to removal efficiency is low, after adding carbon sources can be resolved, the effluent TN low, could meet the emission requirements.6.in the research of adding carbon sources,the UCT system can deal with the Wastewater which C/N is 4,but the UCT system need 7.so the UCT system is much better than the A2/O system in the low C/N dispose,before and after adding carbon sources ,UCT system have higher TP removal efficiency than A2/O system.7. If not considering other indicators, the system can meet emission standards except nitrogen. Considering all the indicators, after the system run stably, the removal rate of CODcr stabilized at about 85%, ammonia nitrogen was above 80%, and total nitrogen was about 50%; after adding carbon, the removal rate of total nitrogen was about 85% of and total phosphorus higher than 50%. The parameters of the stable-running system were: the amount of water was 2.0t/h; aeration rate was 30m3/h; digestion liquid reflux ratio was 200%; hypoxia liquid reflux ratio was 200%; sludge recycle ratio was 100%; gas-water ratio was 15; aerobic zone DO concentration was between 2.5mg/L to 4mg/L; the sludge concentration was between 3000mg/L to 3500mg/L; the sludge age was 20 days; methanol dosage was 0.4L/h.