Effect of influent C/N ratios on denitrifying phosphorus removal characteristics in the A2/O-BCO process
ZHANG Miao, PENG Yong-zhen, ZHANG Jian-hua, WANG Cong, WANG Shu-ying, ZENG Wei
Engineering Research Center of Beijing, Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124, China
A two-sludge system combined anaerobic/anoxic/oxic with biological contact oxidation process (A2/O-BCO) was used to treat domestic wastewater. By adding sodium acetate to adjust influent carbon/nitrogen ratio (C/N=2.44 ~ 8.85), the denitrifying phosphorus removal characteristics of the system were investigated. The results showed that nitrification performance (anoxic denitrifying loading) and poly-β-hydroxyalkanoates (PHA) storage and utilization were mainly influenced by organic matter, which further effected the nitrogen and phosphorus removals. When the influent C/N ratio was 4 ~ 5, COD, TN and PO43--P removals reached to 88%, 80% and 96% respectively, which achieved high-efficiency removal of organic matter, nitrogen and phosphorus simultaneously. The material balance analysis of carbon revealed that COD removal in the A2/O reactor was 71.86% ~ 77.28% of the total COD removal, and COD removal in the BCO reactor only accounted for 2% ~ 12%, where the efficient utilization of carbon source in the A2/O-BCO process was the main reason to achieve deep denitrification and phosphorus removal under the condition of low C/N. In addition, through the correlation analysis of C/N with aeration rate, nitrate recycling ratio and anaerobic/anoxic reaction time, the optimal operation strategy of the A2/O-BCO process was proposed.
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