Temperature-dependent growth of Aeromonas in drinking water - Executive Summary - Aeromonas grows faster at higher temperatures, but the maximum counts remain the same

It is advisable to produce drinking water with the least possible amount of sediment and nutrients, so as to limit the growth of Aeromonas in the distribution network. Laboratory tests have shown that a higher water temperature leads to more rapid growth of Aeromonas, but that the maximum Aeromonas count is also possibly dependent on the amount and type of nutrients. This is the outcome of the Joint Research Programme study into the impact of higher drinking water temperatures on the growth of Aeromonas, which is the legal parameter for regrowth. The drinking water temperature is expected to rise as a result of climate change. Since the drinking water temperature cannot be influenced, and water practice shows that Aeromonas growth is temperature-dependent, the question then concerns the impact of increased temperature on the growth of Aeromonas.

Interest: impact of increasing water temperature on the growth of Aeromonas – The Aeromonas bacterium is an indicator for regrowth in the distribution network and must remain below 1000 kve/100 ml. However, during hot periods the legal standard for Aeromonas is exceeded in several distribution areas. Although Aeromonas is not a hazard for public health, these exceedances are not desirable. The impact of the water temperature on the growth of Aeromonas is only known from water practice. Data from the drinking water utilities reveal that the increase of Aeromonas in the drinking water distribution network begins in the spring/early summer, when the water temperature in the distribution area rises above 8-10oC.
It is expected that climate change will cause a rise in the temperature of surface water – which is used to produce drinking water – but also that the soil will become warmer, causing the drinking water to heat up further. This can raise the drinking water temperature above the legal standard of 25oC, without any counter measures being possible. Higher temperatures can potentially lead to stronger growth of Aeromonas in the distribution network. However, the impact of higher temperatures on the growth of Aeromonas is unknown; this is the subject investigated in this report.

Report – This research is described in the report Temperatuurafhankelijke groei van Aeromonas in drinkwater (BTO-2018.097).