Abstract:

Simultaneous nitrogen and phosphorus removal could be realized by denitrifying phosphorus removal system. However, a shortage of organic carbon for wastewaters with low COD/N ratio can result in adding carbon source to overcome the limitation of low organic carbon. By adding carbon sources to adjust influent COD/N ratio around 4.3,the role of various carbon source in the A²/O-BCO(anaerobic anoxic oxic-biological contact oxidation)process was investigated. The batch tests were used to further research the substrate storage and conversion of activated sludge with various additional carbon sources. These results showed that the substrate storage and utilization characteristics were influenced by the type of influent carbon, which further effected the nitrogen and phosphorus removals. When sodium propionate was the additional carbon source, PO₄^3--P removal steadily maintained around 94%, however, the removal efficiency of TIN was 70.82%. For sodium acetate, TIN removal reached to 74%, but the average removal efficiency of PO₄^3--P was 89.90%. The conversion analysis of carbon source revealed that the content of PHA was mainly PHV with adding sodium propionate in the anaerobic phase. On the contrary, the proportion of PHB increased with adding sodium acetate. In the anoxic phase, the effect of PHB and PHV degradation by DPAOs was closely related to its content. Compared to PHB, PHV is liable to be absorbed by DPAOs. When sodium propionate was used as additional carbon source, the higher PHV degradation rate and productivity efficiency were observed, which improved the phosphorus absorption rate. In addition, the optimal operation strategy of the A²/O-BCO process with various sources was proposed.

Key words: additional carbon sources, denitrifying phosphorus removal, A²/O-BCO process, substrate storage and utilization

摘要：

反硝化除磷系统可实现氮、磷的同步去除，但在处理实际低C/N污水时，常需补充碳源以解决碳源不足的问题。采用A²/O-BCO（anaerobic anoxic oxic-biological contact oxidation）反硝化除磷系统，通过投加两种常用的外碳源控制进水C/N在4.3左右，考察碳源类型（丙酸钠、乙酸钠）对A²/O-BCO系统长期运行效果的影响，并采用批次试验进一步探究不同外加碳源条件下活性污泥的内碳源贮存和利用特性。结果表明：碳源种类的变化会改变微生物的底物贮存和利用特性，进而影响系统的脱氮除磷效果。当采用丙酸钠为外加碳源时，PO₄^3--P去除效果稳定在94%左右，实现了磷的高效去除，但TIN的去除率仅为70.82%；而以乙酸钠为外加碳源时，系统TIN的平均去除率可以达到74%，但磷的出水浓度出现波动现象，平均去除率仅为89.90%。碳源转化分析表明，厌氧条件下，进水丙酸钠含量增多，PHV的合成比例增加，相反，乙酸钠含量增多，PHB合成比例增多；缺氧条件下，DPAOs对PHB和PHV的降解效果与其含量相关，丙酸钠作为外碳源时，PHV的降解速率高且微生物产能效率高，因此PO₄^3--P吸收速率较快。此外，本文提出了不同外加碳源条件下系统的优化运行策略。

关键词: 外加碳源, 反硝化除磷, A²/O-BCO系统, 底物贮存与利用