Micropollutants are known for their potential to significantly affect the aquatic environment. The environmental impact of these substances is expressed particularly by their persistency, bioaccumulation potential and toxicity. Effective test methods regarding their ecological toxicity are currently under research. Municipal wastewater treatment works (WWTWs) are among the most important entry paths of micropollutants into surface water bodies. Recent investigations proved that oxidative and adsorptive methods can be applied cost-effectively for micropollutant removal. Various removal units have been already implemented in full-scale in municipal WWTWs in Germany, Switzerland and France. In the Netherlands treatment units including micropollutant removal have been constructed in hospitals. Further full-scale plants are currently being planned. The paper presents an overview on the general impacts of micropollutants, effective techniques for their removal and current implementations in Europe.
Keywords activated carbon, adsorption, micropollutant removal, ozonation, wastewater treatment
The term “micropollutants” basically represents the residues of chemicals occurring in the water-soilair matrix in trace amounts from microgram to pictogram per litre and literally underlines the low concentration range of the substances. Pharmaceuticals, cosmetic products, artificial musk, industrial auxiliary chemicals, pesticides and biocides are among the substance groups considered as micropollutants. These are released into the hydrological cycle through urban and agricultural sources.
The effects of micropollutants in aquatic ecosystem are not very well known yet. However, there are clear indications for their significant impact potential, particularly considering the long-term impacts. Reasons for this are (1) their potential to accumulate into aquatic organisms and human bodies (bioaccumulation), (2) their toxicity and (3) their resistance to degradation in the environment (persistency). Regulations on their emission and discharge are thus decisive for improving the aquatic environment and surface water quality.
The Water Framework Directive 2000/60/EC (CEC, 2000) is the European-wide legislation tackling the hazards and risks arising from priority substances. It aims for good ecological and chemical conditions in surface water bodies and regulates the monitoring and measures of the EU Member States towards improving the surface water quality. In 2013, the new Directive 2013/39/EC (CEC, 2013) came into force, amending the Directives 2000/60/EC and 2008/105/EC (CEC, 2008), which previously amended the Directive 2000/60/EC, as regards to the list of priority substances. More specifically, twelve new substances were introduced and thus, 45 compounds are now classified as priority substances. A remarkable number of the substances given in the priority list, particularly biocides and industrial auxiliary chemicals are considered as micropollutants due to their nature, impact and concentration range. There is a waiting list with another 100 substances that will be assessed for inclusion during the next review process. Regarding the known effects of micropollutants and the expected future developments such as increased consumption of the chemicals associated with the demographic rise, intensified actions shall be taken towards minimising the release of micropollutants into surface water bodies (ARGE KOM-M.NRW, 2015).
The entry pathways of micropollutants into surface water bodies are diverse. Current findings about the hazardous feature of these chemicals first raise the question whether they can be replaced by harmless alternatives. This is partly possible and should be a primary goal for the policy makers. However, it is very unlikely that a full replacement of these chemicals by the harmless ones will be possible, as certain hazardous features, such as endocrine manipulation (hormonal pharmaceuticals) or fatal effects (antibiotics, pesticides) are desired effects. Thus to prevent the release of micropollutants in the aquatic environment, a multi-barrier concept is required. This implies actions towards preventing micropollutants from entering the hydrological cycle at the source as well as elimination measures. Regarding the latter, a broad spectrum of micropollutants enter surface water bodies through municipal wastewater treatment works (WWTWs), making them an important source for micropollutant release. Thus, advanced wastewater treatment technologies can contribute to the micropollutant removal significantly.
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