Wastewater Discharge Impact on Drinking Water Sources Along the Yangtze River (China)

Science of the Total Environment 599–600 (2017) 1399–1407 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Wastewater discharge impact on drinking water sources along the Yangtze River (China) Zhuomin Wang a,DongguoShaoa, Paul Westerhoff b,⁎ a State Key Laboratory of Water Resources & Hydropower Engineering Science, Wuhan University, Luojia Hill, Wuhan 430072, PR China b School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-3005, United States HIGHLIGHTS GRAPHICAL ABSTRACT • First estimates for indirect (de facto) potable wastewater reuse potential in Yangtze River. • Levels of de facto reuse ranged from b1% to N14%. • Demonstrate strategy to predict unplanned wastewater reuse using limited datasets • Shows interconnected hydrologic na- ture of growing cites in Asia article info abstract Article history: Unplanned indirect (de facto) wastewater reuse occurs when wastewater is discharged into surface waters up- Received 25 March 2017 stream of potable drinking water treatment plant intakes. This paper aims to predict percentages and trends of de Received in revised form 8 May 2017 facto reuse throughout the Yangtze River watershed in order to understand the relative contribution of wastewa- Accepted 9 May 2017 ter discharges into the river and its tributaries towards averting water scarcity concerns. The Yangtze River is the Available online 17 May 2017 third longest in the world and supports more than 1/15 of the world's population, yet the importance of waste- fi Editor: D. Barcelo water on the river remains ill-de ned. Municipal wastewater produced in the Yangtze River Basin increased by 41% between 1998 and 2014, from 2580 m3/s to 3646 m3/s. Under low flow conditions in the Yangtze River near Keywords: Shanghai, treated wastewater contributions to river flows increased from 8% in 1998 to 14% in 2014. The highest Wastewater levels of de facto reuse appeared along a major tributary (Han River) of the Yangtze River, where de facto reuse Drinking water can exceed 20%. While this initial analysis of de facto reuse used water supply and wastewater data from 110 cit- Reuse ies in the basin and 11 gauging stations with N50 years of historic streamflow data, the outcome was limited by Hydrology the lack of gauging stations at more locations (i.e., data had to be predicted using digital elevation mapping) and Urban lack of precise geospatial location of drinking water intakes or wastewater discharges. This limited the predictive Pollution capability of the model relative to larger datasets available in other countries (e.g., USA). This assessment is the first analysis of de facto wastewater reuse in the Yangtze River Basin. It will help identify sections of the river at higher risk for wastewater-related pollutants due to presence of—and reliance on—wastewater discharge that could be the focus of field studies and model predictions of higher spatial and temporal resolution. © 2017 Elsevier B.V. All rights reserved. ⁎ Corresponding author. E-mail address: [email protected] (P. Westerhoff). http://dx.doi.org/10.1016/j.scitotenv.2017.05.078 0048-9697/© 2017 Elsevier B.V. All rights reserved. 1400 Z. Wang et al. / Science of the Total Environment 599–600 (2017) 1399–1407 1. Introduction Fig. 1 showsthelocationsofriversandmajorpopulationcenterswithin the basin. The population density varies spatially, and the impact of up- Increasing economic development and human migration stress stream cities on downstream water quality is a major concern. All prov- water resources and water quality in many regions. Wastewater inces in China publish annual water resource bulletins that include discharged into surface waters represents a potentially reliable water macro data about water consumption and provide valuable information source, but it can convey chemical and microbial pollutants to cities on wastewater production within cities. Limited hydrological and drinking water intakes located downstream. Reclamation of water (stream flow) data exist along the entire length of the Yangtze and trib- after treatment in modern wastewater treatment plants (WWTPs) utaries. Consequently, the Yangtze River Basin is an important case for will likely be an important yet currently unrealized part of sustainable researching de facto reuse. The dataset for this paper included wastewa- water resource management (Bellona and Drewes, 2007). In the ter information collected from the water resources bulletins such as United States of America (USA), the National Academy of Engineering water intake and water consumption of each city and wastewater dis- published a report on wastewater reuse, and among the top ten re- charge of each province. We acknowledge that untreated wastewater search needs for human health, social, and environmental studies is flowed into the Yangtze River for centuries, but the recent advent of ad- quantifying the extent of de facto reuse (Needs, 2012). De facto reuse vanced sewage collection and centralized treatment (Wang et al., 2011) is the unplanned or incidental presence of treated wastewater in a along with major shifts in population density within urban centers in water supply source, and it occurs when treated wastewater is China is resulting in a smaller number of point sources for treated discharged from a WWTP into surface waters upstream of potable wastewater discharges. Portions of the Yangtze River are vulnerable to drinking water treatment plant (DWTP) intakes (see Fig. SI.1). The pres- water scarcity, but less so than other major rivers in Asia (Finlayson ence of treated wastewater in drinking water supplies increases the risk et al., 2013; Liu et al., 2013; Varis et al., 2012; Webber et al., 2015). Un- of water quality contamination from pharmaceuticals or other trace or- derstanding the contribution of wastewater flows into the Yangtze ganics, pathogens, and inorganic pollutants (Barnes et al., 2008; Cheng, River can contribute towards avoiding water scarcity. 2003; Duirk et al., 2011; Focazio et al., 2008; Fono and McDonald, 2008; China has the largest population in the world and has been rapidly Kaplan, 2013; Schwarzenbach et al., 2010). Estimates of de facto reuse urbanizing and investing in water infrastructure, yet many regions are exist in the USA and some European countries, but few estimates exist water stressed (Chu et al., 2004; Zhang et al., 2016). The goal of this for Asia (Kugathas et al., 2012; Williams et al., 2012). De facto reuse is paper is to estimate levels and patterns in de facto reuse within widespread and is increasing with population growth and increased China's largest river basin and, while doing so, demonstrate how de sewage collection. It is not uncommon to have a substantial portion of facto reuse can be estimated when geospatial or hydrologic national source waters originally derived from an upstream wastewater dis- datasets are limited. Assessing the extent of de facto wastewater reuse charge (Rice et al., 2013). Models capable of predicting de facto reuse in Yangtze River Basin required the following activities: (1) data com- are relevant for estimating impacts on downstream drinking water sup- pletion by reasonable assumptions and digital elevation model (DEM), plies for people. Model predictions also identify river reaches that con- (2) development of a model within the ArcGIS framework to determine tain an elevated fraction from wastewater origin, which may therefore spatial relationships between every city, (3) quantification of accumu- contain higher concentrations of chemical and microbial pollutants. lated wastewater of each city, (4) examination of wastewater percent- Wastewater discharges may pose water quality risks to downstream ages under low flow stream conditions in different years, and ecosystems and people who rely upon the river as drinking water (5) analysis about the relationship between population density and de source, but it simultaneously provides a renewable and sustainable in- facto reuse. This assessment is the first analysis of de facto wastewater stream flow that contributes towards a reliable water supply. WWTP reuse in Yangtze River Basin, which will help drinking water manage- discharges are a main source of pharmaceuticals and many other ment in the basin. In addition, it will provide a framework on how to micro pollutants in the environment, nutrients that influence stream use limited datasets to access de facto reuse in other locations. ecology, and pathogens that pose ecological and human health risks (Chen et al., 2009; Hajj-Mohamad et al., 2014; Maier et al., 2015). GIS- 2. Materials and methods based models can facilitate the assessment of potential impacts from wastewater, and several water quality models have been developed The primary datasets for this study included the quantity of water for this purpose (Kugathas et al., 2012; Williams et al., 2012; Johnson intake, water consumption, water discharge, and river streamflow in et al., 2013; Price et al., 2010; Rowney et al., 2011). For example, the the Yangtze River Basin. Data were mined from several sources: base national-scale GIS based model that includes modules for WWTP, Geographic Information System (GIS) layers were obtained from DWTP, and river reaches in the USA was useful for conducting a national China Geological Survey for topography, stream networks, and city assessment of de facto reuse occurrence on DWTPs and assessing the boundaries. Water resources bulletins were used

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