Abstract:

The simultaneous conversion of ammonia nitrogen and sulfate in anaerobic environment was discovered and nitrogen removal by sulfate reduction ammonia oxidation (SRAO) was proposed 20 years ago. This process can use the inherent sulfate in wastewater as electron acceptor to oxidize ammonia nitrogen to nitrogen without additional organic matter and secondary pollutant under anaerobic condition. Based on the recent research and understanding of relevant literatures, this paper summarized the research history, influencing factors and possible conversion pathways of nitrogen and sulfur of SRAO, further clarified the appropriate substrate concentration and environmental conditions of the occurrence of nitrogen removal by SRAO. Due to the complex microbial communities in the reactor, SRAO bacteria coexists with SRB, HDB and SAD bacteria, with their complex multi-reaction synergism in the reactor causing the SRAO phenomenon. Firstly, the process can be started either under the condition of influent organic matter or without organic matter. The starting methods can be divided into three categories according to the electron acceptors of ammonia nitrogen: gradual replacement of nitrite nitrogen by sulfate, simultaneous addition of nitrite nitrogen and sulfate, and addition of sulfate only. Anammoxoglobus sulfate and Bacillus benzoevorans were identified as SRAO functional bacteria. Secondly, the type of reactor, the source of seed sludge, nitrogen to sulfur ratio of influent, organic matter and other factors will impact on the efficiency of substrate conversion. The elimination method can be used to determine whether the oxidation of ammonia nitrogen is sulfate, and the oxidation products of ammonia nitrogen change with the change of the molar ratio of nitrogen to sulfur. Although both SRAO and anaerobic methanogenesis were carried out under anaerobic conditions, no SRAO phenomenon had been found in anaerobic methanogenesis system. Multiple bacteria metabolized synergistically was found in the reactor where SRAO phenomenon was first discovered but methanogens did not dominate. At present, the research on SRAO is still mainly in a laboratory scale, future studies can be carried out from the following aspects: (1) shortening start-up time and improving removal efficiency of substrate, (2) exploring the conversion pathway of ammonia nitrogen and sulfate and key influencing factors, and (3) identifying functional bacteria. This paper aims to provide comprehensive information for future theoretical research and promote its application in practical wastewater treatment.

Key words: biological nitrogen removal, sulfate reduction ammonia oxidation, sulfate reduction, synergistic effect, influencing factors

摘要：

20多年前，人们就发现厌氧环境下氨态氮和硫酸盐的同步转化现象，并提出了硫酸盐型厌氧氨氧化（SRAO）脱氮说。该途径可以在厌氧条件下以废水中固有的硫酸盐为电子受体将氨态氮氧化为氮气，无需额外添加有机物，也不产生二次污染。该文通过对近年来国内外有关文献资料的研究理解，从SRAO研究历程、影响因素及氮硫可能的转化途径等方面进行了总结，理清了SRAO脱氮的发生需要适宜的基质浓度及环境条件，由于反应器内微生物菌群复杂，SRAO菌与SRB、HDB和SAD菌等共存，构成了SRAO现象是反应器内复杂的多反应协同作用的结果。首先，该过程既可以在进水有有机物的条件下启动，也可以在进水没有有机物的条件下启动；启动方式可根据进水中所加入氨态氮的电子受体分为三类：硫酸盐逐步替代亚硝态氮，同时加入亚硝态氮和硫酸盐，仅加入硫酸盐；Anammoxoglobus sulfate和Bacillus benzoevorans为已明确的SRAO功能菌。其次，反应器的类型、种泥来源、进水氮硫比、有机物等因素会对基质转化效率产生一定的影响。对于氨态氮被氧化是否是硫酸盐作用可采用排除法来确定，氨态氮的氧化产物随氮硫摩尔比的变化而变化。虽然SRAO和厌氧产甲烷都是在厌氧条件下进行的，但是在厌氧产甲烷系统中没有发现SRAO现象，主要是首次发现SRAO现象的反应器内多种菌群相互协同代谢但产甲烷菌不占主导地位。目前关于SRAO研究还主要处于实验室规模，之后的研究可从以下几方面展开：（1）缩短启动时间，提高基质的去除效率；（2）探究氨态氮与硫酸盐的转化途径及关键影响因素特征；（3）相关功能菌的鉴别。本文旨在为今后的理论研究提供综合信息并促进其在实际废水处理中的应用。

关键词: 生物脱氮, 硫酸盐型厌氧氨氧化, 硫酸盐还原, 协同作用, 影响因素