Aquifer storage and recovery is recognized in the USA as having a significant role for inter-season storage of drinking water, and in Europe and Australia also for its potential for water treatment. However a better knowledge of water quality changes during aquifer storage and recovery, along with better understanding of sustainable treatment processes in aquifers is necessary to enable water utilities to take advantage of this technique. The usefulness of aquifer storage and recovery to improve the quality of injected water is being investigated at several sites. Specific interest is on the attenuation rates of microbial pathogens and organic compounds (both natural and synthetic) in saturated groundwater at artificial recharge sites. Microbial pathogens of particular interest are enteric viruses and protozoa, while the organic chemicals being investigated include several disinfection-by-products and endocrine disruptors. The aim is to encapsulate the data obtained from this investigation into models for the prediction of changes in water quality, and which can be used by water utilities and regulators to evaluate pretreatment requirements for aquifer storage and recovery. This will also improve accuracy of information for the protection of the health of consumers and the environment.