Abstract
The salinity effect on anammox bacteria has been widely reported; however, rare studies describe the microbial dynamics of anammox-based process response to the introduction of real seawater at mainstream conditions. In this study, an anammox process at mainstream conditions without pre-enriching anammox bacteria was shifted to the feeds of a synthetic wastewater with a portion of seawater mixture. It achieved over 0.180 kg-N/(m3 day) of nitrogen removal rate with an additional seawater proportion of 20% in the influent. The bacterial biodiversity was significantly increased with the increase of seawater proportions. High relative abundance of anammox bacteria (34.24–39.92%) related to Ca. Brocadia was enriched and acclimated to the saline environment. However, the introduction of seawater caused the enrichment of nitrite-oxidizing Ca. Nitrospira, which was responsible for the deterioration of nitrogen removal efficiency. Possible adaptation metabolisms in anammox bacteria and other nitrogen transforming bacteria are discussed. These results highlight the importance of microbial diversity for anammox process under the saline environments of 20% and 40% seawater composition.
Highlights
Anaerobic ammonium-oxidizing-based processes have attracted increasing attention due to its advantages: less oxygen requirement, no carbon addition, and less sludge production (Du et al 2015; Lackner et al 2014; Ma et al 2017; Siegrist et al 2008)
Anammox process was successfully applied for high-strength wastewater treatment (Ma et al 2016), and in recent, an increasing of studies supported its feasibility for mainstream (Agrawal et al 2018; Laureni et al 2016)
The effects of real seawater on anammox process for nitrogen-rich wastewater treatment had been reported (Qi et al 2018), limited reports describe under saline low nitrogen loading conditions, especially for the evolution of microbial dynamics with different proportions of seawater feed
Summary
Anaerobic ammonium-oxidizing (anammox)-based processes have attracted increasing attention due to its advantages: less oxygen requirement, no carbon addition, and less sludge production (Du et al 2015; Lackner et al 2014; Ma et al 2017; Siegrist et al 2008). The effects of real seawater on anammox process for nitrogen-rich wastewater treatment had been reported (Qi et al 2018), limited reports describe under saline low nitrogen loading conditions, especially for the evolution of microbial dynamics with different proportions of seawater feed. This study characterized the microbial evolution in anammox process for low-strength wastewater with different proportion of real seawater. Investigation was made for the reactor performance and each corresponding microbial structure at different seawater proportions, with special attention on the anammox bacteria, AOB, and NOB. Their potential adaptation metabolisms towards seawater-based wastewater in Anammox bacteria and other nitrogen transforming bacteria were addressed
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