Towards the development of an improved mass balance and water quality index based grey water footprint model

With the increasing pressure on water resources, there is a need to better understand water use throughout the supply chain of goods and services to identify opportunities to alleviate this stress. Therefore, a proper assess-ment of the water footprint is necessary. The grey water footprint (GWF), defined as the freshwater required to dilute excess pollutants discharged into the environment, is an important indicator and has various models which are disputed on their ability to effectively capture the extent of water pollution. This study suggests an improved model based on two stages. The first stage consists of a mass balance used to amend the concentrations of the pollutants. As for the second stage, it consists of calculating the GWF based on the Water Quality Index (WQI) which is the most popular water assessment tool used by researchers. The suggested model allows a better breakdown of the GWF required to assimilate the pollution as it outputs different ranges based on the water quality sought as opposed to a single value or range traditionally obtained using existing models. In addition, the comparison between the improved model and the existing ones demonstrates that the existing models under-estimate the GWF if a medium to excellent water quality is to be sought.