Microbial quality of rainwater supplies in developed countries: a review

The current paper examines the reported microbial quality of rainwater supplies. The majority of microbial contamination derives from debris and faecal material deposited on the roof surface, principally from birds. The prevalence and level of contamination varies widely, both in terms of indicator organisms and pathogens. Gastrointestinal pathogens such as Campylobacter spp., Salmonella spp., Cryptosporidium spp. and Giardia spp. have all been isolated from harvested supplies, although these may not always be of types infective to humans. In the UK, there are currently no regulations in respect to the microbial quality of harvested rainwater for non potable use, although there are generally standards relating to the required plumbing to ensure that potable and non potable supplies remain separate.