Microbiological quality of groundwater in UK urban aquifers: do we know enough?

The contamination of groundwater by pathogenic microorganisms is acknowledged as an important health risk worldwide. Traditionally, public health microbiologists have concentrated on pathogen transport via contaminated surface waters. This has reinforced a common perception among hydrogeologists and water supply professionals that groundwater represents a relatively microbiologically safe source of drinking water. As a result, the presence of microbial pathogens in aquifer systems is still largely unknown. This is worrying, especially in urban aquifers in which renewed interest is being shown. Several studies have demonstrated the contamination of groundwater with pathogens, in particular viruses. Our understanding of the factors that affect the survival and transport of microorganisms in the subsurface is limited and the mechanisms by which they are transported to deep groundwaters are unclear; however, the implications for public health may be significant.