不同碳氮比对海水养殖废水脱氮效果的影响

工厂化海水养殖废水C/N（碳氮比）较低，有效碳源不足，生物脱氮工艺往往由于缺乏碳源而受到抑制.为揭示脱氮工艺中不同过程对碳源匮乏的敏感程度，应用A/O-MBBR（缺氧/好氧-移动床生物膜反应器）处理模拟海水养殖废水，探讨进水C/N降低（从12降至1）对反应器运行效果的影响，并根据EPS（胞外聚合物）、AMO（氨单加氧酶）、NOR（亚硝酸盐氧化酶）、NIR（亚硝酸盐还原酶）、NR（硝酸盐还原酶）的活性，分析碳源不足对不同脱氮过程的抑制状况.结果表明:①C/N降低时，COD_Cr、NH₄+-N、NO₂--N的去除率均未下降，自养型的氨氧化、亚硝化过程不受影响，AMO和NOR活性提高.②缺氧区pH降低，ρ（DO）升高，NO₃--N的去除率显著降低，C/N为5时开始积累，NR活性明显下降.③异养反硝化反应电子供体出现由外碳源向内碳源和EPS的转换，缺氧区EPS含量逐渐减少，C/N为1时比C/N为6时减少了47%.研究显示，碳源不足是造成海水养殖废水生物反硝化不彻底的主要原因，为了实现高效脱氮，需要在海水养殖废水处理过程中严格控制ρ（DO）并且提供足够的碳源. 

Effect of Different C/N Ratio on Nitrogen Removal of Mariculture Wastewater

Industrial mariculture wastewater commonly contains a low COD_Cr/total nitrogen (C/N) ratio and insufficient effective carbon source. Thus, the biochemical nitrogen removal process is often inhibited due to the lack of carbon source. In order to reveal the sensitivity of different stages of nitrogen removal process to the lack of carbon sources, an anoxic/oxic-moving bed biofilm reactor (A/O-MBBR) was used to treat simulated mariculture wastewater, and the effect of different influent C/N (C/N decreased from 12 to 1) on the performance of the reactor was investigated. The inhibition of nitrogen removal process was analyzed based on the change of extracellular polymer (EPS), activity of ammonia monooxygenase (AMO), nitrite oxidoreductase (NOR), nitrite reductase (NIR) and nitrate reductase (NR). The results indicated that: (1) The removal rates of COD_Cr, NH₄⁺-N and NO₂^--N did not decrease, and the autotrophic ammonia oxidation and nitrification were not affected. The activity of AMO and NOR increased. (2) The pH of anoxic zone decreased and the content of dissolved oxygen increased. The removal rate of NO₃^--N decreased significantly. When the C/N was 5, NO₃^--N began to accumulate. The NR activity decreased significantly. (3) The electron donor of heterotrophic denitrification transformed from external carbon source to internal carbon source and EPS. The content of EPS in anoxic zone decreased gradually. When C/N was 1, EPS decreased by 47% compared to C/N 6. This research showed that the lack of carbon source is the main reason for the incomplete biological nitrogen removal in mariculture wastewater. In order to achieve efficient nitrogen removal, it is necessary to strictly control the dissolved oxygen and add enough carbon source in mariculture wastewater treatment.