Our water pipes crawl with millions of bacteria (Phys.org)
"Researchers from Lund University in Sweden have discovered that our drinking water is to a large extent purified by millions of "good bacteria" found in water pipes and purification plants. So far, the knowledge about them has been practically non-existent, but this new research is about to change that."
Global Drinking Water Quality Index Development and Sensitivity Analysis Report (UN)
"Any number of water quality measurements can serve, and have already been used, as indicators of water quality. However, there is no single measure that can describe overall water quality for anyone body of water, let alone at a global level."