Researchers from Adelaide University and Flinders University tested rainwater from 100 household tanks across Adelaide and the Adelaide Hills, finding bacteria linked to gastroenteritis and other infections in a number of tanks.
The study found Campylobacter bacteria in 13 per cent of tanks, Salmonella in 10 per cent, Shigella in three per cent (all linked to gastroenteritis) and Pseudomonas aeruginosa (which causes other infections) in 12 per cent.
Bacteria were also detected in tanks used for drinking water.
Two-thirds of the households surveyed (67 per cent) said they used their tank water for drinking and cooking, highlighting the importance of understanding what is in the water people are consuming.
Lead researcher Dr Mira Cooper, from Adelaide University’s School of Physics, Chemistry and Earth Sciences, said the findings were a reminder that rainwater collected from a roof did not necessarily remain as clean as it appeared.
“Rainwater might look clean, but once it lands on a roof and flows through gutters and into a tank, it can pick up bacteria, metals and other contaminants along the way,” Dr Cooper said.
The researchers also found small numbers of tanks contained levels of metals including cadmium, lead, arsenic and manganese above Australian health-based drinking water guidelines.
Metal tanks (as opposed to tanks made from plastic) were more likely to have elevated metal levels, while tanks that had not been maintained well were also associated with higher metal concentrations.
The researchers say further work is needed to determine whether the bacteria detected in the tanks were alive and capable of causing infection, as the testing identified bacterial DNA rather than proving that the bacteria were viable.
