Owing to improved analytical processes, the presence of more and more micropollutants has been substantiated in the Swiss aquatic environment. However, many of these substances have not so far been regulated in the Water Protection Ordinance.
They accompany us on a daily basis: chemicals in textiles, detergents, cosmetics and paints. Many of these substances can be found again in our aquatic environment and drinking water resources, where they occur in very low concentrations of nano- to micrograms per litre and are therefore termed micropollutants. Micropollutants usually deploy their possible toxic effects on aquatic organisms in the long term – by stealth, as it were – which makes it difficult to uncover the nexus between cause and effect.
Effects difficult to gauge
The situation in the aquatic environment is complex. For instance, there are frequent occurrences of strongly fluctuating pollution and pollutant mixtures made up of different substances. Besides the original substances, their transformation products should also be taken into account when the risks of substances are assessed, for they are usually more easily soluble in water and thus more mobile.
The nanoparticles that are already present in more than 800 products are also problematical. If we do not want to experience any scenario similar to that caused by, say, asbestos fibres, then it is important to assess them. The greatest challenge, however, is the assessment of so-called multiple stressors: aquatic organisms do not only suffer from chemical pollution, they are additionally influenced by stressors such as increased temperature, droughts and UV radiation. Eawag records the environmental behaviour and impact of micropollutants in a holistic way and develops concepts that will serve to reduce or prevent the presence of micropollutants in the aquatic environment. For this reason, it cooperates with, among others, the Federal Office for the Environment (cf. box) and industry.
Measures at various levels
One possibility of reducing micropollutants in the aquatic environment is to equip sewage plants with technologies such as ozone treatment and filtration with activated carbon. In addition, it is important to define effect-based quality objectives for the aquatic environment. They should replace the value of 0.1μg/l that is generally applicable to pesticides and be fixed for pollutants that have not been regulated so far.
Measures at source prevent micropollutants from entering wastewater flows and the aquatic environment in the first place: in production, for instance, production processes should switch to ecologically compatible chemicals. It is also promising to separate strongly polluted wastewater, for example from hospitals or industrial plants, from normal wastewater and treat it separately.
