| Poor denitrification capacity is the typical problem of municipal wastewater treatment plant. In order to improve denitrification efficiency of CASS process in Dongyang watewater treatment plant, through actual research of the wastewater treatment plant in Dongyang, the pilot plant of sewage treatment plant was made. Further the research of influent composition and sewage sludge nature, simulation model of the pilot plant and wastewater treatment plant were established based on the use of GPS-X, and the predictive analysis were launched. Through long term laboratory experimental by pilot plant, the optimum conditions and control measures of pilot plant effluent were acquired, and the wastewater treatment plant during the actual operation were further optimized. The main conclusions were obtained as follows.(1) Test results of influent and effluent showed that, measured values of TN and NH3-N were higher than the design values, and TP measured values were close to design value, while the measured values of COD were far less than the design value. Influent C/N and C/P were significantly different from the designed values. Effluent COD, NH3-N were lower than the design limits, however, the vast majority of the effluent TN and TP exceeded B level standard. Influent COD components analysis showed that, BCOD was about 30% of total COD, and carbon source starvation and poor biodegradability may have a greater impact on the system of nitrogen and phosphorus removal.(2) GPS-X simulation and small pilot periodic tests showed that, regardless of 6h, 4.8h or 4h, influence of cycle on the effluent could be ignored, COD and NH3-N standards could be stabilized, the effluent TN, TP did not meet the B level standard. TN highest reduction rate was about 20%. And the reactor almost had no capacity of biological phosphorus removal.(3) When the aeration time was reduced from 1 h to 0.5 h, ammonia was still achieved full nitrification, meanwhile, aeration energy consumption was saved. However, carbon savings were not enough to improve denitrification effect.(4) Matrix dosing experiments confirmed that, when influent TN about 60 mg/L, dosage of 20 mg COD/L Na Ac or glucose could be short-term to maintain the stability of the effluent TN. When influent TN was about 40 mg/L, 20 mgCOD/L glucose and methanol were cast automaticlly. The results showed that the effluent COD concentration were 20 mg/L or less, the effluent NH3-N were also close to zero. And A level standard was met. Compared with Na Ac and glucose, methanol was more economic.(5) According to the concentration of actual influent COD, TN and COD component analysis, dosage of external carbon were identified as CODex/?TN=3.45~ 3.81, the mean was 3.63. Short term dosing test according to the conclusions of small pilot test analysis showed that, effluent COD and ammonia met B level, meanwhile, effluent TN concentration decreased and finally also met B level when dosing.(6) Short term field tests showed that, under conditions of the design cycle and adjustment cycle, the effluent COD, NH3-N met B level standard, and TN concentration of the effluent decreased at 20 mg/L, which were partially achieved, and effluent TP with the recommended chemical phosphorus removal mode resulted in the significant improvement. Analog values and measured values of indicators had small error. Process sampling of the main reaction were shown that, as the reaction proceeds, all indicators showed a downward trend and fluctuated over time, and actual nitrogen removal was limited. |
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