Extending improvements of eutrophication and water quality via induced natural mixing after artificial mixing in a stratified reservoir

Chengcheng Wen; Kai Li; Tinglin Huang; Sai Wang; Yun Tang; Gang Wen; Haihan Zhang; Xiaohua Li; Xiaochun Cai

doi:10.1016/j.jenvman.2022.116048

Extending improvements of eutrophication and water quality via induced natural mixing after artificial mixing in a stratified reservoir

J Environ Manage. 2022 Nov 15:322:116048. doi: 10.1016/j.jenvman.2022.116048. Epub 2022 Sep 5.

Authors

Chengcheng Wen¹, Kai Li², Tinglin Huang³, Sai Wang⁴, Yun Tang⁵, Gang Wen⁶, Haihan Zhang⁷, Xiaohua Li⁸, Xiaochun Cai⁹

Affiliations

¹ Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China. Electronic address: hitchengchengwen@xauat.edu.cn.
² Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China. Electronic address: likai@xauat.edu.cn.
³ Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China. Electronic address: huangtinglin@xauat.edu.cn.
⁴ Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China. Electronic address: 1461556083@qq.com.
⁵ Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China. Electronic address: 1085880735@qq.com.
⁶ Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China. Electronic address: hitwengang@163.com.
⁷ Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China. Electronic address: zhanghaihan@xauat.edu.cn.
⁸ Lijiahe Reservoir Management Co., Ltd., Xi'an, 710016, China. Electronic address: 1393665805@qq.com.
⁹ Lijiahe Reservoir Management Co., Ltd., Xi'an, 710016, China. Electronic address: 232421244@qq.com.

PMID: 36067671
DOI: 10.1016/j.jenvman.2022.116048

Abstract

Induced (natural) mixing proposed by our teams can solve a big problem of low-energy water situation improvement of stratified reservoirs by minimizing operating periods of water-lifting aerators (WLAs) to advance a complete natural mixing. Here, the mechanisms influencing water situation via induced mixing were systematically explored using a combination of multi-water-environment assessment methods including trophic level index (TLI), water quality index (WQI), and minimum WQI (WQI_min) based on long-term field data (i.e., non-operational and operational years of WLAs). The results showed that induced mixing after WLA deactivation improved the levels of eutrophication and water quality (into "light-eutrophic" and "good" status) with a decrease in TLI values (56.0-56.2) and increase in WQI (79.0-79.9) and WQI_min (81.5-89.3) values, compared to mixing of the non-operational year (TLI: 69.6, WQI: 73.4, WQI_min: 76.1). Induced mixing was launched by deactivating the WLAs in cooling seasons (i.e., in late September within a subtropical monsoon climate zone), which advanced and prolonged the periods of naturally complete mixing by 2-3 months. Water temperature (WT), Dissolved oxygen (DO), relative water column stability (RWCS) and inflow were primary drivers for the water situation succession in the study years. Induced mixing extended the well-oxygenated and mixed conditions (temperature difference <1.0 °C, DO > 8.5 mg/L, RWCS< 20) following artificial mixing to improve the water status from single index level (improvement of 18.8%-73.7% than mixing before the operational years) to integrated evaluation results by changing WT, DO, and RWCS. This study presents a successful case for energy-saving pollution control using mixing systems.

Keywords: Drinking water reservoir; Energy saving; Eutrophication; Induced natural mixing; Water degradation; Water environment improvement.

MeSH terms

China
Environmental Monitoring / methods
Eutrophication*
Oxygen
Phosphorus / analysis
Seasons
Temperature
Water Quality*

Substances

Phosphorus
Oxygen