Summary

No extensive studies have been undertaken to determine the presence and level of Legionella in wastewaters in New Zealand. However, there have been incidental findings during source tracing investigations for Legionella. This report provides a review of available literature for Legionella in recycled wastewater and greywater. Wastewater recycling, especially the reuse of greywater, is increasingly seen as one approach to addressing the challenges posed by population growth, urbanisation, and climate change for accessing or conserving drinking water. However, there is a risk that the quest to find more sustainable solutions for water management could have unintended consequences if factors such as adequate wastewater treatment and storage are not addressed, or the water is utilised in a manner that increases the exposure risk to pathogens present in the water. There is empirical evidence that Legionella bacteria can survive and multiply in wastewater and greywater, and legionellosis cases have been associated with wastewater and wastewater treatment plants. However, there is significantly less evidence when only recycled greywater is considered, and there have been no published cases of legionellosis from these systems.