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Overlooked pathways of denitrification in a sulfur-based denitrification system with organic supplementation.
Water Research ( IF 11.4 ) Pub Date : 2019-09-12 , DOI: 10.1016/j.watres.2019.115084
Yan-Ying Qiu 1 , Liang Zhang 2 , Xintong Mu 1 , Guibiao Li 1 , Xiangqing Guan 1 , Jiaying Hong 1 , Feng Jiang 3
Affiliation  

Elemental sulfur-driven autotrophic denitrification (SADN) is a cost-effective approach for treating secondary effluent from wastewater treatment plants (WWTPs). Additional organics are generally supplemented to promote total nitrogen (TN) removal, reduce nitrite accumulation and sulfate production, and balance the pH decrease induced by SADN. However, understanding of the impacts of organic supplementation on microbial communities, nitrogen metabolism, denitrifier activity, and SADN rates in sulfur-based denitrification reactors is still limited. Here, a sulfur-based denitrification reactor was continuously operated for 272 days during which six different C/N ratios were tested successively (2.7, 1.5, 0.7, 0.5, 0.25, and 0). Organic supplementation improved TN removal and decreased NO2- accumulation, but reduced the relative abundance of denitrifiers and the contribution of autotrophic nitrate-reducing bacteria (aNRB) to TN removal during the long-term operation of reactor. Predictive functional profiling showed that nitrogen metabolism potential increased with decreasing C/N ratios. SADN was the predominant removal process when the C/N ratio was ≤0.7 (achieving 60% contribution when C/N = 0.7). Although organic supplementation weakened the dominant role of aNRB in denitrification, batch tests for the first time demonstrated that it could accelerate the SADN rate, attributed to the improvement of sulfur bioavailability, likely via the formation of polysulfide. A possible nitrogen removal pathway with multiple electron donors (i.e., sulfur, organics, sulfide, and polysulfide) in a sulfur-based denitrification reactor with organic supplementation was therefore proposed. However, supplementation with a high level of organics could increase the operational cost and effluent concentrations of sulfide and organics as well as enrich heterotrophic denitrifiers. Moreover, microbial community had substantial changes at C/N ratios of >0.5. Accordingly, an optimal C/N ratio of 0.25-0.5 was suggested, which could simultaneously minimize the additional operating cost associated with organic supplementation and maximize TN removal and SADN rates.

中文翻译:

在含有机补充剂的硫基反硝化系统中,反硝化途径被忽略了。

元素硫驱动的自养反硝化(SADN)是一种经济有效的方法,用于处理废水处理厂(WWTP)的二次废水。通常补充其他有机物以促进总氮(TN)的去除,减少亚硝酸盐的积累和硫酸盐的产生,并平衡由SADN引起的pH降低。但是,对基于硫的反硝化反应器中有机物补充对微生物群落,氮代谢,反硝化活性和SADN速率的影响的了解仍然有限。在此,硫基反硝化反应器连续运行272天,在此期间连续测试了六个不同的C / N比(2.7、1.5、0.7、0.5、0.25和0)。有机补充改善了TN的去除并减少了NO2-的积累,但是减少了反硝化剂的相对丰度,并减少了反应器长期运行过程中自养硝酸盐还原菌(aNRB)对TN去除的贡献。预测性功能分析表明,氮代谢潜力随C / N比的降低而增加。当C / N比≤0.7时,SADN是主要的去除过程(当C / N = 0.7时,达到60%的贡献率)。尽管有机补充削弱了aNRB在反硝化中的主导作用,但首次批量试验表明它可以加快SADN速率,这归因于硫生物利用度的提高,可能是通过形成多硫化物来实现的。具有多个电子给体(例如,硫,有机物,硫化物,因此提出了一种在硫基反硝化反应器中添加有机物的方法。但是,补充高含量的有机物可能会增加运营成本和硫化物和有机物的废水浓度,并富集异养反硝化剂。此外,在> 0.5的C / N比下,微生物群落发生了显着变化。因此,建议的最佳C / N比为0.25-0.5,这可以同时最大程度地减少与有机补充相关的额外运营成本,并使TN去除率和SADN率最大化。C / N比> 0.5时,微生物群落发生了重大变化。因此,建议的最佳C / N比为0.25-0.5,这可以同时最大程度地减少与有机物补充相关的额外运营成本,并使TN去除率和SADN率最大化。C / N比> 0.5时,微生物群落发生了重大变化。因此,建议的最佳C / N比为0.25-0.5,这可以同时最大程度地减少与有机物补充相关的额外运营成本,并使TN去除率和SADN率最大化。
更新日期:2019-09-12
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