Fig. 6From: Getting in control of persistent, mobile and toxic (PMT) and very persistent and very mobile (vPvM) substances to protect water resources: strategies from diverse perspectivessource water. The gap increases when the concentrations of the pollutants increase, or when environmental quality standards are loweredRemoval Requirement Index for PMT substances at the intake of Nieuwegein (River Rhine), based on the methodology of Pronk et al. (2021) as described in https://iwaponline.com/ws/article/21/1/128/77954/A-water-quality-index-for-the-removal-requirement. The Water Quality Removal Requirement Index is an indicator sum parameter that describes the gap between the standards in the Dutch drinking water act, and the quality of the Back to article page