Microbial action and mechanisms for Cr(VI) removal performance by layered double hydroxide modified zeolite and quartz sand in constructed wetlands

Xiangling Zhang; Shuangjie Zhao; Jingtian Gao; Yu Lei; Ye Yuan; Yinghe Jiang; Zhouying Xu; Chunyan He

doi:10.1016/j.jenvman.2019.06.017

Microbial action and mechanisms for Cr(VI) removal performance by layered double hydroxide modified zeolite and quartz sand in constructed wetlands

J Environ Manage. 2019 Sep 15:246:636-646. doi: 10.1016/j.jenvman.2019.06.017. Epub 2019 Jun 15.

Authors

Xiangling Zhang¹, Shuangjie Zhao², Jingtian Gao³, Yu Lei², Ye Yuan², Yinghe Jiang², Zhouying Xu², Chunyan He²

Affiliations

¹ School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan, 430070, China. Electronic address: zhangxiangling@whut.edu.cn.
² School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan, 430070, China.
³ School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan, 430070, China; School of Energy and Environment, Inner Mongolia University of Science & Technology, Baotou, 014010, China.

PMID: 31212217
DOI: 10.1016/j.jenvman.2019.06.017

Abstract

This study was conducted to evaluate the performance underlying the removal of hexavalent chromium Cr(VI) associated with Zn-layered double hydroxides (Zn-LDHs)-modified substrates utilized in simulated constructed wetlands (CWs) from a microbial perspective. To accomplish this, Zn-LDHs-modified substrates (zeolite and quartz sand (QS)) were synthesized at various Zn²⁺/Al³⁺ and Fe³⁺ molar ratios by co-precipitation under alkaline conditions. The experimental group was then compared with a control group to determine the microbial action responsible for Cr(VI) removal during the Cr(VI) removal experiments. The removal experiment revealed that the average Cr(VI) removal rates of the Zn-LDHs-modified substrates were superior to those of natural substrates. Subsequent evaluation of the microbial structure by Illumina high-throughput sequencing revealed that the relative abundance of Novosphingobium, Brevundimonas, Methylophilus, and Acidovorax related to Cr(VI) removal was relatively high in Zn-LDHs-modified substrates. Moreover, the extracellular polymeric substance (EPS) content was significantly influenced by the Zn-LDHs coating according to the relative microbial experiments. Similar trends were observed in enzyme activity. Taken together, these findings illustrated that the Zn-LDHs coating had a significant impact on microbial action, and the Cr(VI) removal efficiency of the Zn-LDHs-modified QS (zeolite) substrate was better than that of the natural substrate because of intracellular and extracellular removal mechanisms. Briefly, the microbial action of Zn-LDHs-modified QS played an important role in Cr(VI) removal, since the EPS content possessed the appropriate concentrations. Moreover, the microbial activity of ZnAl-LDHs-modified QS (zeolite) may have been higher than that of ZnFe-LDHs-modified QS (zeolite) because Al had a stronger promoting effect on Cr(VI) bio-removal than Fe. Therefore, the microbial Cr(VI) removal supported by ZnAl-LDHs-modified QS is a better choice for CWs.

Keywords: Constructed wetlands; Cr(VI) removal; High-throughput sequencing; Microbial action; Zn-LDHs-modified substrate.

MeSH terms

Adsorption
Chromium
Extracellular Polymeric Substance Matrix
Hydroxides
Quartz
Wetlands*
Zeolites*

Substances

Hydroxides
Chromium
Zeolites
Quartz
chromium hexavalent ion