A holistic analysis of marine anammox bacteria-dominated anammox respond to Zn(II) in saline wastewater treatment: from bio-stimulation to rapid collapse

Abstract

This work first unraveled the response mechanism of marine anammox bacteria (MAB)-dominated anammox process to Zn(II) in treating saline wastewater. Low Zn(II) doses (≤ 3 mg/L) enhanced MAB activity, with the highest total nitrogen removal rate (TNRR) of 1.33 kg/(m³·d) achieved at 3 mg/L Zn(II). Additionally, the relative abundance of MAB (Candidatus Scalindua) sharply increased from 9.2% to 46.1%. It further increased to 53.0% at 5 mg/L Zn(II), even though TNRR collapsed to 0.22 kg/(m³·d). Furthermore, the production of nitrite reductase, nitrate reductase and hydrazine dehydrogenase was stimulated, with enzymatic activity and heme c content first increasing and then decreasing, reaching the maximum at 3 mg/L Zn(II). More extracellular polymeric substances were also secreted to resist high Zn(II) doses (≥ 4 mg/L) stress. This work clearly demonstrated that the addition of appropriate doses of Zn(II) is an effective strategy to stimulate MAB activity in the treatment of saline wastewater.

Graphical abstract

Keywords

Saline wastewater / Zn(II) / Nitrogen removal / Marine anammox bacteria / Microbial community

Highlight

	● MAB activity was stimulated at 1–3 mg/L Zn(II) in saline wastewater treatment.
	● Nitrogen removal performance rapidly collapsed at 5 mg/L Zn(II).
	● More EPS were secreted by MAB to resist high Zn(II) doses (≥ 4 mg/L) stress.
	● Nitrogen removal was affected by Zn(II) through regulating the enzymatic activity.

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