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Bacteria in drinking water

Many producers in rural areas use rainwater for drinking water in their tasting rooms and restaurants. Normally the rainwater is not treated the way that reticulated town water is. This can be a health risk due to the presence of bacteria in the water. The source of the bacteria is normally due to the presence of birds, rodents, possums etc. on the tank collection roof area, or in the guttering that feeds into the tank. This is easy to test and easy to treat and should be, and usually is, a regular task for the production management.

One of our customers gets us to do routine microbiological analysis on their tank water. A recent sample revealed harmful E.coli and Thermotolerant coliforms to be present. These are the critical tests that are recommended by the Australian Drinking Water Guidelines.

To rule out poor sampling procedure as the cause of the bacteria, the customer asked us to re-test the water sample after their water taps had been thoroughly cleaned and particular care was taken while sampling the water using the sterile water bottles we supplied.

We then re-tested the water for the presence of these microbes with the fresh samples. After analysis, once again we found the presence of E.coli and Thermotolerant coliforms in their water. According to the Australian Drinking Water Guidelines, there should be none of these harmful microbes present in water that will be used for human consumption.

Discussions with the customer revealed that a UV sterilisation system was in place in the water feed line to the production facility, therefore our results suggested that this system was no longer working as it should. Previous periodic analysis of the winery water had always returned a negative bacterial result.

The winery UV system was therefore checked and the decision was taken to replace it. Subsequent analysis of the water after the UV system replacement showed no E.coli or Thermotolerant coliforms.

The lesson from this experience was that the process put in place to monitor the system had worked previously, but that these systems are not foolproof. If you use tank water for client and staff consumption, it would be very wise to have the water tested regularly. The time between testing will depend upon several factors that need to be considered.

If you are interested in looking at the increasingly common UV sterilisers, your local irrigation/pump shop is the first place to go for some good information.