Water Quality Responses during the Continuous Mixing Process and Informed Management of a Stratified Drinking Water Reservoir

Zizhen Zhou,Tinglin Huang,Yang Li,Shilei Zhou,Yue Liu,Weijin Gong,Meiying Cao

doi:10.3390/su11247106

Abstract

Aeration and mixing have been proven as effective in situ water quality improvement methods, particularly for deep drinking water reservoirs. While there is some research on the mechanism of water quality improvement during artificial mixing, the changes to water quality and the microbial community during the subsequent continuous mixing process is little understood. In this study, we investigate the mechanism of water quality improvement during the continuous mixing process in a drinking water reservoir. During this period, we found a reduction in total nitrogen (TN), total phosphorus (TP), ammonium-nitrogen (NH4-N), iron (Fe), manganese (Mn), and total organic carbon (TOC) of 12.5%–30.8%. We also measured reductions of 8.6% and 6.2% in TN and organic carbon (OC), respectively, in surface sediment. Microbial metabolic activity, abundance, and carbon source utilization were also improved. Redundancy analysis indicated that temperature and dissolved oxygen (DO) were key factors affecting changes in the microbial community. With intervention, the water temperature during continuous mixing was 15 °C, and the mixing temperature in the reservoir increased by 5 °C compared with natural mixing. Our research shows that integrating and optimizing the artificial and continuous mixing processes influences energy savings. This research provides a theoretical basis for further advancing treatment optimizations for a drinking water supply.

Highlights

There are an increasing number of reservoirs being used as drinking water sources for humans
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Based on this study and our previous research, we could conclude that aeration and mixing can destroy the stratification of the reservoir and activate the metabolism ability and abundance of indigenous microbes in the reservoir

Summary

Introduction

There are an increasing number of reservoirs being used as drinking water sources for humans. Reservoirs are an important drinking water source, they are subjected to considerable water quality problems such as eutrophication and oxygen depletion [1]. Reservoir operation strategies affect biogeochemical processes associated with the cycling of nutrients, nitrogen and organic matter [2,3]. Water quality problems have often been associated with algal overproduction, leaching of pollutants from sediments, and incoming storm water runoff [4]. These mechanisms may seriously compromise the safety of a water supply. The removal of nitrogen and organic matter from drinking water reservoirs is gaining research attention [7,8]. One of the major concerns about the production of drinking water is represented by disinfectant by-products (DBPs), which can appear after using disinfectants to treat water with a high concentration of organic compounds [9,10,11]

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