Removal of micropollutants and microplastics: Solutions for the 4th cleaning step
Micropollutants and microplastics pollute our waters. Municipal sewage treatment plants are reaching the limits in their cleaning services. Planning for a 4th purification stage happens across countries of the Global North. However, this only solves part of the problem. At Wasser 3.0, we research solutions for the simultaneous removal of micropollutants and microplastics. This makes prevention measurable and protects water in the long run.
Status quo
Conventional wastewater treatment in municipal sewage treatment plants happens in three stages. These processes remove on average more than 95% of organic matter. Despite this supposedly very good cleaning performance, substances that are readily water-soluble and poorly biodegradable in particular remain in the wastewater. These compounds are known as anthropogenic trace substances or micropollutants.
The concentration of micropollutants in wastewater is in the range of “micrograms per liter” (= one millionth of a gram per liter). In municipal wastewater, they often derive from products that are used in households, public facilities, industry, trade, and agriculture. Due to their stability (persistence), they remain in the water cycle over the long term and can, therefore, also have a negative impact on the quality of drinking water.
Substances of particular concern are those that, due to known biological effects, negatively influence water quality and water use. The sources are pharmaceuticals, biocides, pesticides, detergents and cleaning agents, personal care products as well as building materials and utensils.
In relation to the variety of micropollutants that have been found in water bodies so far, only relatively few representatives are known to have specific effects. Measures to reduce the entry of micropollutants into water bodies are, therefore, based on the precautionary idea and with that on the installation of a 4th purification stage in municipal sewage treatment plants.
Ozonation and activated carbon as part of the 4th cleaning stage.
Current state of the art and considerations on economic efficiency make essentially two processes available: ozonation and activated carbon adsorption. Although these processes go beyond current requirements in wastewater treatment provided for by the Water Framework Directive, they have their limitations and, above all, some disadvantages that cannot be neglected.
- Ozonation: By introducing the strong oxidizing agent ozone into the pre-treated wastewater, micropollutants are largely broken down. However, an undefined cocktail of micropollutants and their degradation products emerges, with currently unquantifiable effects on the environment and human health.
- Activated carbon adsorption: Micropollutants can be bound to activated carbon, which is used either as a powder or in granular form. The mechanism of adsorption has been adequately studied. The desorption properties, i.e., the leaching of pollutants caused by competition on the surface of the activated carbon and the docking of so-called "good" natural organic chemical compounds, have not yet been conclusively investigated scientifically.
Most of the projects resulted in additional specific annual costs in the range of €0.10 to €0.25 per m³ of wastewater. The actual costs can differ significantly in individual cases.
A 4th cleaning stage not only causes additional costs, but also has additional effects on the environment - regarding the need for energy and operating resources as well as the amount of waste.
This is exactly where Wasser 3.0 comes in: With new research concepts and technological processes.
Our approach: The 4th cleaning step plus or in short: Wasser 3.0 PE-X® plus We are of the opinion that the 4th cleaning stage urgently needs a holistic assessment regarding micropollutants and microplastics as well as the issues of sustainability and efficiency.
We are, therefore, working on new solutions for the simultaneous removal of micropollutants and microplastics from our wastewater and on ensuring that citizens are transparently informed about wastewater treatment measures. Because water concerns us all.
