Optimization of the pollutant removal in partially unsaturated constructed wetland by adding microfiber and solid carbon source based on oxygen and carbon regulation

Xinhui Zheng; Jian Zhang; Mengting Li; Lin-Lan Zhuang

doi:10.1016/j.scitotenv.2020.141919

Optimization of the pollutant removal in partially unsaturated constructed wetland by adding microfiber and solid carbon source based on oxygen and carbon regulation

Sci Total Environ. 2021 Jan 15:752:141919. doi: 10.1016/j.scitotenv.2020.141919. Epub 2020 Aug 22.

Authors

Xinhui Zheng¹, Jian Zhang², Mengting Li³, Lin-Lan Zhuang⁴

Affiliations

¹ Institute of Marine Science and Technology, Shandong University, Qingdao 266237, China. Electronic address: zhengxh@mail.sdu.edu.cn.
² Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science & Engineering, Shandong University, Qingdao 266237, China. Electronic address: zhangjian00@sdu.edu.cn.
³ Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science & Engineering, Shandong University, Qingdao 266237, China.
⁴ Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science & Engineering, Shandong University, Qingdao 266237, China. Electronic address: zhuanglinlan@sdu.edu.cn.

PMID: 32898802
DOI: 10.1016/j.scitotenv.2020.141919

Abstract

The partially unsaturated constructed wetland was demonstrated to be able to enhance the oxygen supplement for the microbial nitrification. However, the fast gravity flow of wastewater on the smooth surface of substrate in unsaturated zone led to a short contact time between wastewater and biofilm on the surface of substrate for the microbial pollutant oxidation process. While, the strengthened oxygen supplement also consumed organic carbon, intensifying the shortage of electron donator for the denitrification process. To further enhance the efficiency of both nitrification and denitrification processes, two strategies were conducted as follows: (1) adding microfiber in unsaturated zone to extend the hydraulic retention time (HRT) and improve the oxygenating efficiency; (2) adding slow-release carbon source (Poly butylenes succinate, PBS) as electron donor in saturated zone for denitrification. Results showed that the ammonia oxidation efficiency reached up to 97.0% in the microfiber-enhanced constructed wetland. Additionally, adding microfiber provided more sites for microbes and increased the total number of microbes in unsaturated zone. The addition of PBS in the saturated zone obviously improved the denitrification efficiency with the total nitrogen (TN) removal rate raising from 20.6 ± 4.0% to 90.4 ± 2.7%, which excellently solved the problem of poor denitrification efficiency caused by low ratio of carbon to nitrogen (C/N). In conclusion, the association of microfiber and PBS in partially unsaturated constructed wetland finally accomplished the thorough nitrogen removal.

Keywords: Bacterial community; DO microelectrode; Enhanced oxygen supplement; Nitrogen removal; Slow-released organic carbon; Unsaturated zone.