Research On The Domestic Wastewater By The Two-point Influent OAO Process

The actual domestic wastewater with low-carbon, high ammonia and phosphorus was used in the test, and the two point-influent OAO wastewater treatment system was studied, the differences of the water pollutants treatment effect between the winter and summer was contrasted. The reflux ratio r and the total HRT impacting on the treatment effect was studied, and the best running parameters were concluded. The impact of external carbon source and DO for each pollutant removal efficiency, the total nitrogen removal influence and methods were studied, and several operation control recommendations were proposed for the system.The temperature of the actual wastewater was different in summer and winter, the pollutants were more in winter than in summer. With the same methods for the sludge acclimation, the temperature was higher in summer and the microbial activity was better than in winter, so the effect was better. With different temperature during the acclimation, the demand of effluent COD was less than 50mg/L after treatment, and the effluent ammonia kept stably less than 5mg/L, the activity of denitrifying bacteria was worse in summer than in winter, and the influent ammonia concentration was higher in winter than in summer, which was resulted the high ammonia in early acclimatization of winter, but the effluent ammonia was stably at 5mg/L or less after 5 days. Due to the lackness of carbon, the total nitrogen and total phosphorus removal could not be further improved of different water temperature.With the reflux ratio changing, the system effluent COD and ammonia did not change significantly. With the reflux ratio increasing, the total nitrogen and total phosphorus removal showed firstly increased but then decreased, the total nitrogen increased gradually slowly. When r=2, the total nitrogen removal was the best. With the total HRT changing, the system effluent COD, ammonia and total nitrogen removal efficiency increased with the HRT increasing. With the removal of total nitrogen, the aerobic pool of HRT should not be less than 2h. But the removal of the total phosphorus by HRT was not obvious. So it could be considered that the total HRT was 12 h and the reflux ratio was 150~200%.It was studied the effects of different DO in the aerobic denitrification tank with three conditions. Compared and analysised the various reaction pathways and the removal of contaminants in the different pools. With the decrease of DO, aerobic denitrification rate increased. In the same condition, aerobic denitrification rate decreased due to lower nitrate concentration in the aerobic tank.The sewage with low-carbon was used in the test, microbials were in a long-term lack of carbon, which was suitable for denitrifying bacterias to survive. After acclimation training, nitrobacterias had advantages in the system. In three conditions, effluent ammonia was stability less than 2mg/L. The sludge sedimentation showed better performance after adding the ethanol, and the COD performed lower. In the second condition, it came to 84.3% of the total nitrogen removal. In the third condition, the glucose added to the sewage, which increased the carbon volume, the aerobic denitrification showed good condition in the low DO aerobic denitrification tank. So the carbon was an important fact to aerobic denitrification.