A hybrid water-quality-index and grey water footprint assessment approach for comprehensively evaluating water resources utilization considering multiple pollutants

The grey water footprint (GWF) is effective in helping to evaluate the sustainable and efficient use of water resources. Traditionally, GWFs have been used to assess individual pollutants wherein only the highest GWF value is typically used. However, multiple pollutants coexist in water, and the characteristics of water resources are defined collectively by all contaminants present. To date, few studies have attempted to specifically consider impacts of multiple pollutants on GWFs; however, GWFs based on multiple pollutants could provide a global picture of spatiotemporal changes in water quality as a whole. Accordingly, this study proposes an improved method to assess GWFs under multiple pollutants. The proposed method is to initially determine a wide range of GWFs, after which different GWF values are refined using a binary search algorithm until meeting a given water quality target. One commonly used method (the Water Quality Index (WQI) from the Canadian Council of Ministers of the Environment (CCME)) was used in this study to assess water quality based on multiple pollutants. We also calculated the water pollution level (WPL) based on associative GWFs and compared results to test the effectiveness of the improved method. China was used as a case study to illustrate this improved method. Results showed that compared to the traditional method, the improved method could reduce 25% of values of GWFs while maintaining a "Good" water quality ranking. Even under a 50% reduction, the improved method was still able to maintain a "Fair" ranking. Based on the traditional method, regions where WPLs were >1 totaled approximately 63.59% in 31 regions throughout China; however, corresponding results under different water quality targets based on the improved method were approximately 46.54% and 36.87%. The improved method provides an efficient tradeoff between water quality and quantity management. It has also shown that existing studies which only considered individual pollutants may have overestimated GWFs and WPLs values. (C) 2019 Elsevier Ltd. All rights reserved.