Groundwater sources provide approximately 30% of water supplies in England (and 5% in Wales). There are known to be over 100 microbiological pathogens that can contaminate groundwater, including viruses. Whilst water companies in England and Wales do include the risks from viruses in their drinking water safety plans, there is no monitoring for viruses conducted by the industry. It is well documented that the standard bacterial indicators do not accurately provide indications of viral loading in source waters.
In 2012, the Inspectorate published a study which examined viruses in surface waters and the ability of treatment to remove them. The study found that most virus removal occurred in the first stage treatment (particle removal). Ground water often undergoes minimal treatment and commonly will not have a particle removal stage. It is therefore critical that water companies understand the risk from viruses in order to ensure adequate disinfection is maintained to mitigate that risk.
As part of the research, monitoring was carried out at eight sites representing four different aquifer types. The study will be interesting reading for water quality planners. It recommends a source pathway, receptor risk model, similar to that developed for cryptosporidium. Generally viral sources are linked to human faecal contamination (although some are animal in origin) and so risk assessment should focus on sewage collection, transport and discharge in relation to aquifers and the permeability of the strata