Iron scraps enhance simultaneous nitrogen and phosphorus removal in subsurface flow constructed wetlands

Yuhui Ma; Wanqing Dai; Peiru Zheng; Xiangyong Zheng; Shengbing He; Min Zhao

doi:10.1016/j.jhazmat.2020.122612

Iron scraps enhance simultaneous nitrogen and phosphorus removal in subsurface flow constructed wetlands

J Hazard Mater. 2020 Aug 5:395:122612. doi: 10.1016/j.jhazmat.2020.122612. Epub 2020 Apr 3.

Authors

Yuhui Ma¹, Wanqing Dai², Peiru Zheng², Xiangyong Zheng³, Shengbing He⁴, Min Zhao²

Affiliations

¹ School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
² School of Life and Environmental Science, Wenzhou University, Wenzhou, 325000, China.
³ School of Life and Environmental Science, Wenzhou University, Wenzhou, 325000, China. Electronic address: 00121051@wzu.edu.cn.
⁴ School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China. Electronic address: Shengbing_he@163.com.

PMID: 32361175
DOI: 10.1016/j.jhazmat.2020.122612

Abstract

In rural domestic wastewater treatment using subsurface constructed wetland system (SFCWs), the lack of a carbon source for denitrification and limited phosphorus uptake are responsible for low removal of nitrogen and phosphorus, and a suitable substrate is therefore, necessary. Iron is an important component in nitrogen and phosphorus biogeochemical cycles. Few studies have addressed the application of iron in SFCWs. Therefore, we constructed SFCWs that used iron scraps as a substrate. Enhanced nitrification, denitrification and removal of phosphorus were observed. The large proportion of nitrite-oxidising bacteria present in CWs with iron scraps (CW-T) compared to gravel beds indicated that iron may enhance ammonium (NH₄⁺) oxidation. More nitrate-reducing bacteria related to Fe and autotrophic denitrifying bacteria were discovered in the back zone of CW-T and these enhanced denitrification process. Phosphate (PO₄^3-) reacted with ferrous ion (Fe²⁺) and ferric ion (Fe³⁺) to generate the precipitant. Moreover, Fe³⁺ reacted with water to generate iron oxide (FeOOH) that had a large adsorption capacity for phosphorus. After six months of operation, average NH₄⁺-N, total nitrogen and total phosphorus removal rates were 66.98 ± 13.37 %, 71.26 ± 13.57 % and 93.54 ± 6.64 %, respectively. Iron scraps can potentially be utilised in SFCWs in rural domestic wastewater treatment.

Keywords: Constructed wetlands; Iron cycle; Iron scraps; Nitrogen removal; Phosphorus removal.

Publication types

Research Support, Non-U.S. Gov't