Antibiotic resistance in surface water and water treatment

Over the past few decades the use of antibiotics by humans and for veterinary purposes has grown sharply. Doctors in the Netherlands exercise restraint in prescribing antibiotics, but their use in the Dutch veterinary sector is very high. Antibiotics, transformation products and antibiotic resistant bacteria (ARB) end up in the environment, where they have undesirable effects on the microbial population.

Before this project began, Q-PCR tests had been developed that made it possible to detect genes for different types of antibiotic resistance. Limited screening detected some of these genes in surface water, but also at some treatment sites. The literature also shows that these genes can be detected in surface water and at treatment sites. However, given the limited range of the pilot screening, the possibility of assessing the true meaning of these results was limited.

The current project involves a more extensive measurement programme, in which the presence of ARG is ascertained at several sites and on a number of occasions. It provides a clearer picture of the presence of ARG in raw water and in treated water, after it has been submitted to different treatment processes.

Sampling at intake points and in treatment

The project begins by inventorizing relevant ARG and applying the current set of Q-PCR tests, in order to monitor the presence of ARG. We then elaborate a research set-up to examine the transfer of ARG to bacteria that occur naturally in the drinking water (treatment) environment.

We then research the surface water at different intake points in the Netherlands, a number of times a year, for the presence of ARG. We also collect samples in the treatment to get more insight into the presence of ARG in different treatment processes. For control purposes, we also carry out our sampling programme at a groundwater treatment site, where no anthropogenic influences are expected. Moreover, we will study whether ARG can be transferred from the ARB, which can end up in surfaces water through discharges, to bacteria that occur in drinking water treatment.

Insight into the extent of ARG

At the end of 2016, this research will give us a picture of the extent to which ARG occur in raw water and in the treatment. We will therefore be able to assess whether current treatment processes are sufficiently capable of controlling ARG. Moreover, on the basis of this information, we will be able in the future to determine whether the types and numbers of ARG increase. If it appears that the pressure of ARG on water treatment and on water in the Netherlands is growing, then this information could be used to tighten requirements applied to treated wastewater, so that the water used to produce drinking water is less exposed to ARG.