Typically, surfactants are discharged of via waste water after use. Due to their pronounced eco-toxicological effect on aquatic organisms, a proper wastewater treatment is key to ensure that surfactants are safe for the aquatic environment. In Europe, wastewater treatment is mandated by legislation and widely implemented in the EU member states. The eco-toxicological effect on the biocoenosis is, among other influencing parameters (e.g. biodegradability), driven by the ratio between the treated wastewater and the receiving fresh water. In northern European countries with a wet climate, dilution factors are generally high (>> 10x), whereas in southern Europe dilution factors may be more critical.
The fact that the surfactants in the water column are undergoing additional fate processes has to be taken into account. Adsorption to suspended particles and sediments, as well as additional biodegradation processes by water-borne microorganisms, will further decrease the concentration of surfactants . According to a central paradigm of eco-toxicology, biodegradation will reduce the eco-toxicological potential of chemical substances. Nevertheless the eco-toxicological profile of the biodegradation products needs to be considered as well.
In addition to the acute (short term) effects, chronic (long term) eco-toxicological effects need to be taken into account. These chronic effects can be attributed to long-term exposure of aquatic organisms to surfactants and their biodegradation products. For the fresh water compartment, fish, daphnia and (unicellular) algae are the marker organisms, representing the three trophic levels of the aquatic food chain.