Performance Of Denitrifying Phosphorus Removal And Nitrification In Pilot-scale Variable-velocity Oxidation Ditch With Fine Bubble

To investigate the removal performance of nutrient, nitrogen and phosphorus of municipal sewage, a novel pilot-scale variable-velocity oxidation ditch with fine bubble was researched. The method of static experiment was used to investigate the performance of denitrifying phosphorus removal and nitrification of activated sludge. Meanwhile, the effect of C/N and C/P on nitrogen and phosphorus removal, the effect of different electron acceptor on phosphorus absorption, the effect of temperature on nitrification rate were analyzed. The experimental results showed that:(1) The pilot-scale system had good removal efficiency on nitrogen and phosphorous in sewage. The COD, ammonia nitrogen, TN and TP removal efficiency were 92%, 96%, 81% and 94%, respectively, and the average concentration of COD, ammonia nitrogen, TN and TP of the effluent were 30.7 mg/L, 1.17 mg/L, 11.4 mg/L and 0.34 mg/L, respectively. The most of indexes, achieved the level A standard of ?Discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002)?, the achieved rate of TP was 84%.(2) Better effect of nitrogen removal in the pilot-scale system was got, when the influent C/N of pilot-scale system was 5-6, while influent C/P had no apparent influence on nitrogen and phosphorus removal. Meanwhile, the system got better phosphorus removal when the influent C/P between 60 and 80.(3) It was obviously found that denitrifying phosphorus removal existed in pilot-scale system. Sludge analysis demonstrated that the proportion of DPBs was estimated to be 61% of total PAOs. Electron acceptors(oxygen, nitrate, nitrite) had significant effects on phosphorus uptake rate and their order was in accordance with oxygen>nitrate>nitrite. The mass ratio of anoxic P uptake and N consumption(Puptake/Nconsumption) of nitrate and nitrite is 0.96 and 0.65, respectively.(4) The pilot-scale system had good capacity of nitrification, the AUR and NUR of activated sludge were 3.89~5.59 mg-N/(g·VSS·h) and 2.98~6.93 mg-N/(g·VSS·h), respectively. The average values of the AUR and NUR were 4.57 mg-N/(g·VSS·h) and 4.63 mg-N/(g·VSS·h).(5) The temperature had great influence on the performance of nitrification, AUR and NUR increased with temperature increased gradually. The activity of AOB and NOB decreased rapidly when the temperature was below 15?. Nitrification activity decreased significantly when the temperature less than 10?.(6) To settle the problem of low sludge concentration, significantly reduce of amount of nitrifying bacteria and high effluent ammonia nitrogen which were caused by ?inverse sludge system failures, some measures such as reducing the influent rate, increasing aeration and reducing the discharge of sludge were taken up. Nitrification performance of sludge was completely recovered after 100 days. The case provided a reference for the operation of the activated sludge system.(7) Using the simplified ASM2 d to simulate the nitrification process of the pilot-scale system, the results of nitrification model was consistent with the actual process of nitrification, the floating range were 0.84 ~ 2.59 mg/L.