In March this year, Jim Service, the chairman of water supply company Actew Corporation, and councillors from the Australian city of Canberra dutifully drank bottles of purified sewage water as they unveiled plans to recycle part of the city’s wastewater into tapwater.

Within days, Professor Peter Collignon, director of infectious diseases and microbiology at the Canberra Hospital, wrote an open letter laying out his concerns about the health implications of the scheme.