Cost-based quantitative-qualitative water footprint considering multiple contaminants

In this study, a Quantitative-Qualitative Water Footprint (QQWFP) is proposed and defined as the total cost of water quantity consumption and the cost of removing the contaminants generated in the water use process. The QQWFP consists of two sub-indicators, Quantitative Water Footprint (WFqt) and Qualitative Water Footprint (WFql), determining the quantity and quality use of water and covers multiple contaminants. Water reuse and water returned to the natural water body are considered in the determination. Unlike existing water footprint indicators, the cost-based water quality and quantity footprints of different water processes are comparable, which enables the user and manager to identify the critical water use sector and the bottleneck of water use (i.e. water consumption or pollution). An added benefit is that the QQWFP can be labelled on the product package and increase the customers’ awareness of water use and saving. The method is demonstrated with a case study of monosodium glutamate (MSG) plant in China. Results showed that to produce 1 t MSG, the QQWFP is 302.1 €, among which the Quantitative Water Footprint is only 2.3 €, and Qualitative Water Footprint is 299.8 €, taking more than 99 % of the total QQWFP. Conclusions indicate the significance of addressing water quality determination and the potential for water quality-oriented industrial water use optimisation