Evaluation of Aeromonas legal standard

The Aeromonas­ standard

Aeromonas in drinking water has been included as a microbiological parameter in the Dutch Drinking Water Decree since the 1980s. Aeromonas is included as an operational parameter and not as a health parameter, since Aeromonas bacteria in drinking water are not pathogenic. However, in the event of standard exceedances, the regulation can require the conduct of investigations into the effects on public health. Currently, Aeromonas exceedances are generally tolerated by the Human Environment and Transport Inspectorate (ILT), partly because it is unclear which regrowth problems (aesthetic or technical complaints, colour and/or taste complaints, sediment accumulation or growth of opportunistic pathogens) can be predicted with Aeromonas.

Literature study and interviews

The objective of this project of the Joint Research Programme of KWR and the water utilities is to evaluate the current Aeromonas standard as laid out in the Drinking Water Decree. This evaluation involves compiling a summary of the key outcomes of various studies conducted over the last decades on the subject of Aeromonas in drinking water, and interviewing different stakeholders (drinking water utilities, the regulator and the advisor to the regulator). This should produce answers to the following research questions:

1. Is Aeromonas a good indicator for regrowth?
2. Is the standard’s level related to the regrowth risk?
3. Is the action required following exceedances realistic?

Evaluations and recommendations

The literature study and interviews should elucidate the current use of Aeromonas as a legal operational parameter and the suitability of Aeromonas as an indicator organism. It should also clarify whether it might be desirable to modify the Aeromonas standard, or whether new regulations might be needed to improve the monitoring of microbiological water quality.