硫酸盐还原氨氧化体系中基质转化途径

NH_4~+与SO_4~(2-)在接种ANAMMOX培养物的条件下发生同步转化的现象得到研究者的关注,并据此认为这是发生了以SO_4~(2-)为电子受体的NH_4~+氧化过程.然而在相关文献报道中存在着一些问题和疑惑.本文利用CFSTR反应器通过接种ANAMMOX微生物研究了NH_4~+与SO_4~(2-)同步转化特征,在进水除氧、非充满的密封条件下,NH_4~+-N平均转化50.8 mg·L~(-1),SO_4~(2-)-S平均转化量达4.5 mg·L~(-1),同时元素分析结果显示观察到的黄色固体不是单质硫而是含铁化合物;而在完全充满的批试反应器中,观察不到NH_4~+的转化,SO_4~(2-)发生明显转化,且转化速率与接种生物量有关.这两种条件下反应器中的ORP有很大的差异.通过分析论证,认为本研究及相关文献观察报道的NH_4~+与SO_4~(2-)同步转化很可能不是ANAMMOX微生物以SO_4~(2-)为电子受体氧化NH_4~+,而是各自独立的反应过程:NH_4~+的氧化是由于反应器运行过程形成的微氧环境所致,而SO_4~(2-)的转化是因微生物衰亡过程释放有机物导致的异养还原.这种转化途径可以澄清和解释相关研究中存在的问题和疑惑.

Conversion Pathways of Substrates in Sulfate-Reducing Ammonia Oxidation System

The phenomenon of simultaneous transformation of ammonium and sulfate under the conditions of inoculating ANAMMOX culture has gotten the attention of researchers. However, there are some problems and doubts reported in the related literature. In this study, the characteristics of ammonium and sulfate synchronous transformation were investigated in a CFSTR via inoculation with ANAMMOX culture. Under the condition of oxygen removal and non-filling, in the unfilled sealed fermentation tank, the average conversion of NH₄⁺-N was 50.8 mg·L^-1 while that of sulfate-sulfur was 4.5 mg·L^-1. Elemental analysis results showed that the observed yellow solid was not elemental sulfur but rather iron-containing compounds. However, no obvious change of ammonium was observed when using a filled sealed batch reactor. Only sulfate transformed significantly, and the transformation rate was affected by the inoculation biomass. Under these two conditions, the ORP in the reactor was completely different. This is an indication that the synchronous transformation of ammonium and sulfate observed in both our study and other related studies is probably not a process mediated by ANAMMOX organisms, in which sulfate acted as the electron acceptor to oxidize ammonium. Actually, ammonium and sulfate transformation were completely independent: ammonium oxidation is due to the micro oxygen environment created by the reactor operation form, whereas sulfate conversion is attributed to the sulfate heterotrophic reduction that results from the organic matter release via microbial decay. This transformation can clarify and explain the problems and doubts reported in the related research.