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Ma J.,Beijing University of Technology | Ma J.,Lanzhou Jiaotong University | Peng Y.-Z.,Beijing University of Technology | Wang S.-Y.,Beijing University of Technology | And 3 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2010

Profiles of oxidation reduction potential (ORP) and pH value were investigated during organic degradation, nitrification and denitrification of advanced nitrogen removal in step-feed cyclic activated sludge technology (CAST) with on-line control treating domestic wastewater, and the relationship among process parameters and variations of organic substances and nitrogens during the treatment process was also established. The results show that based on the characteristic points in pH and ORP profiles to halt aeration and stirring process timely, step-feed CAST with on-line control system is found to perform more effectively so that advanced nitrogen removal is achieved and operation cost is saved as much as possible. When COD and mass concentrations of -N in the influent are 155.0-443.6 mg/L and 57.98-82.40 mg/L, COD and mass concentrations of -N and TN in the effluent are less than 40, 0.5 and 2.0 mg/L, respectively, as step-feed CAST with on-line control adopted. Moreover, the specific denitrification rate is observed to be improved significantly when the temperature of system is 17 °C, 23 and 30 °C. Sufficient organic carbon in influent can increase feeding frequencies, shorten treatment process as well as decrease external carbon source dosage. The phosphorus removal performance is stable and the removal rate can reach 90% when step-feed CAST technology is used.


Ma J.,Beijing University of Technology | Peng C.,Beijing University of Technology | Takigawa A.,Maebashi Institute of Technology | Wang S.,Beijing University of Technology | And 4 more authors.
Water Science and Technology | Year: 2010

A step-feed cyclic activated sludge technology (CAST) with a working volume of 72 L treating real municipal wastewater was operated to examine the effect of varying ratios of influent COD/TN and COD/P on the nutrient removal. With the increased COD/P and COD/TN, the phosphorus and nitrogen removals exhibited an upward trend. The TN removals had a positive linear correlation with the phosphorus removal efficiencies, mainly because the presence of nitrate in the anaerobic zone negatively affected the phosphorus release thus the nitrogen removal process took priority over the phosphorus removal process to utilize the limited carbon source in the influent in step-feed CAST where simultaneous removals of nitrogen and phosphorus were achieved. By employing the effective step-feed strategy with alternating anoxic/oxic operation, efficient phosphorus and nitrogen removals of 95.8 and 89.3% were obtained with lower influent COD/P and COD/TN ratios of 61.9 and 5.2, respectively. It was also found that lower temperature, e.g. 13-16°C, did not deteriorate the phosphorus removal, though the nitrogen removal decreased significantly due to incomplete nitrification. As the temperature increased further, TN removal efficiency increased gradually and nitrogen removal via nitrite pathway was successfully achieved with average nitrite accumulation rate above 90% in the system. © IWA Publishing 2010.


Ma J.,Beijing University of Technology | Peng C.,Beijing University of Technology | Wang L.,Beijing University of Technology | Wang S.,Beijing University of Technology | And 4 more authors.
Water Science and Technology | Year: 2010

The performance of a 18 L step-feed cyclic activated sludge technology (CAST) combined with real-time control treating real municipal wastewater was evaluated. The operation strategies employed pH and oxidation reduction potential (ORP) as on-line control parameters, which can control the durations of oxic and anoxic phases flexibly. The obtained results showed that the studied process had achieved advanced and enhanced nitrogen removal by several phases of consecutive oxic/anoxic periods. Total nitrogen in effluent was lower than 2 mg/L and the average TN removal efficiency was higher than 98%, while only requiring small amount of external carbon source. Unexpected characteristic points in pH and ORP profiles denoting the depletion of nitrate were also observed during the last anoxic phase. Denitrification rate was found to be more dependent on the system temperature compared to nitrification rate. Moreover, a stable and efficient phosphorus removal rate above 90% was achieved by using step-feed strategy which enabled the influent carbon source to be fully used and the favourable condition for phosphorus releasing to be created during the anoxic phases. © IWA Publishing 2010.


Wang L.,Beijing University of Technology | Peng Y.-Z.,Beijing University of Technology | Ma J.,Beijing University of Technology | Liu Y.,Standard Water Co. | Ma N.-P.,Standard Water Co.
Huanjing Kexue/Environmental Science | Year: 2010

The effects of different COD/TN and HRTS (hydraulic retention time of select) on nutrients removal were investigated by using an alternating anoxic/oxic CAST(cyclic activated sludge technology) fed with municipal wastewater. The results showed that various COD/TN and HRTS had a bigger influence on the nitrogen removal efficiency rather than the COD removal efficiency. As the influent C/N ratios were about 2.6 and 3.5, ammonia was removed by 98% and TN removal efficiency was increased from 62.9% to 76.2% and 72.1% to 84.6%, respectively, by increasing the HRTS from 1.8 h to 5 h. When the COD/TN ratio was increased to about 4.4, TN removal efficiency was decreased from 86.3% to 58.2% by enlarging the HRTS, which was due to the incomplete nitrification of ammonia. It was also observed that both of increasing the COD/TN and HRTS could improve the phosphorus removal performance of the system. Furthermore, effluent of CAST reached the demanded A of integrated wastewater discharge standards(GB 18918-2002) when the COD/TN and HRTS were 4.4 and 1.8 h, respectively.

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