Advanced oxygenation efficiency and purification of wastewater using a constant partially unsaturated scheme in column experiments simulating vertical subsurface flow constructed wetlands

Xinhui Zheng; Lin-Lan Zhuang; Jian Zhang; Xiangzheng Li; Qian Zhao; Xiran Song; Cheng Dong; Jiayi Liao

doi:10.1016/j.scitotenv.2019.135480

Advanced oxygenation efficiency and purification of wastewater using a constant partially unsaturated scheme in column experiments simulating vertical subsurface flow constructed wetlands

Sci Total Environ. 2020 Feb 10:703:135480. doi: 10.1016/j.scitotenv.2019.135480. Epub 2019 Nov 12.

Authors

Xinhui Zheng¹, Lin-Lan Zhuang², Jian Zhang³, Xiangzheng Li⁴, Qian Zhao⁴, Xiran Song⁴, Cheng Dong⁴, Jiayi Liao⁴

Affiliations

¹ Institute of Marine Science and Technology, Shandong University, Qingdao 266237, China. Electronic address: zhengxh77@163.com.
² 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.
³ Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science & Engineering, Shandong University, Qingdao 266237, China; State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China. Electronic address: zhangjian00@sdu.edu.cn.
⁴ Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science & Engineering, Shandong University, Qingdao 266237, China.

PMID: 31740061
DOI: 10.1016/j.scitotenv.2019.135480

Abstract

The presence of sufficient dissolved oxygen (DO) in a constructed wetland (CW) is vital to the process of removing ammonia nitrogen and organics from wastewater. To achieve total nitrogen removal, which is characterised by enhanced ammonia nitrogen removal, this study offers an efficient strategy to increase the oxygen supply by establishing constant unsaturated zones and baffles in simulating constructed wetlands (SCWs). Henceforth, this strategy is addressed as a partially unsaturated SCW. A centrally located high tube was set up inside the wetland to create an unsaturated zone at a higher level. The effectiveness of the unsaturated zone to supplement the oxygen content was evaluated by comparing with controls (an unaerated SCW and an aerated SCW). The results show the chemical oxygen demand removal rate (85 ± 6%) in the partially unsaturated SCW was equivalent to that in the aerated SCW (83 ± 6%), while the ammonia nitrogen removal rate was 11 times higher compared to that of the unaerated SCW. The removal potential of the partially unsaturated SCW under different HRT (hydraulic retention time)s (12, 24, and 36 h) was examined, and the 36 h-SCW performed the best in the removal of organics and nitrogen. The mechanisms behind the unsaturated zone strategy were studied by analysing water and microbe samples along the pathway. The results from the water quality indicators and the quantitative polymerase chain reactions along the pathway showed the unsaturated zone contributed to the removal of primary organics and ammonia nitrogen. The superior performance of unsaturated zone strategy was discussed further using the enrichment of ammonia-oxidising bacteria, mass of oxygen uptake, and baffle design. The results indicate that the amoA gene/16s rRNA gene abundance ratio and the oxygen uptake (336 ± 44 g m^-³ d^-¹) in the partially unsaturated SCW was higher than that observed in the two controls.

Keywords: Ammonia nitrogen removal; Constructed wetland; High oxygen supply; Organics removal; Unsaturated zone.

MeSH terms

Ammonia
Biological Oxygen Demand Analysis
Nitrogen
Waste Disposal, Fluid / methods*
Wastewater
Wetlands*

Substances

Waste Water
Ammonia
Nitrogen