Microbiological Values of Rainwater Harvested in Adelaide.

In Australia, rainwater is an important source of water for many households. Unlike municipal water, rainwater is often consumed untreated. This study investigated the potential contamination of rainwater by microorganisms. Samples from 53 rainwater tanks across the Adelaide region were collected and tested using Colilert™ IDEXX Quanti-Tray*/2000. Twenty-eight out of the 53 tanks (53%) contained . Samples collected from ten tanks contained at concentrations exceeding the limit of 150 MPN/100 mL for recreational water quality. A decline in was observed in samples collected after prolonged dry periods. Rainwater microbiological values depended on the harvesting environment conditions. A relationship was found between mounted TV antenna on rooftops and hanging canopies; and abundance. Conversely, there was no relationship between seasonality and or roof and tank structure materials and . In several tanks used for drinking water, samples collected prior to and after filtration showed that the filtration systems were not always successful at completely removing . These results differed from a study undertaken in the laboratory that found that a commercially available in-bench 0.45 µm filter cartridge successfully reduced in rainwater to 0 MPN/100 mL. After running a total of 265 L of rainwater which contained high levels of through the filter (half of the advertised filter lifespan), the filter cartridge became blocked, although remained undetected in filtered water. The difference between the laboratory study and field samples could be due to improper maintenance or installation of filters or recontamination of the faucet after filtration. The presence of in water that is currently used for drinking poses a potential health concern and indicates the potential for contamination with other waterborne pathogens.