Advanced Treatment
Micropollutants & Quaternary Treatment
Trace organic contaminants that conventional treatment removes only partially — and the additional stage the recast EU directive introduces for larger plants.
What Are Micropollutants?
Micropollutants are trace organic substances — pharmaceutical residues, personal-care products and certain industrial chemicals — present at very low concentrations. Conventional secondary treatment removes them only partially, which is why an additional stage, quaternary treatment, is increasingly required. The recast Directive (EU) 2024/3019 introduces a quaternary-treatment requirement for larger plants on a defined timeline.
Quaternary Treatment Options
Ozonation
Ozone oxidises a broad range of micropollutants. It works best on well-treated, low-solids effluent and is often followed by a biological polishing step to handle oxidation by-products.
ExploreActivated Carbon
Powdered (PAC) or granular (GAC) activated carbon adsorbs micropollutants onto its surface. Choice between PAC and GAC depends on load, footprint and how the spent carbon is managed or regenerated.
ExploreEngineering Note
Frequently Asked Questions
Micropollutants are trace organic substances such as pharmaceutical residues, personal-care products and certain industrial chemicals present at very low concentrations. Conventional secondary treatment removes them only partially, which is why additional (quaternary) treatment is increasingly required for larger plants.
Quaternary treatment is an additional stage specifically targeting micropollutants, typically using ozonation or activated carbon (powdered or granular). It follows secondary and, where present, tertiary treatment. The recast Directive (EU) 2024/3019 introduces a requirement for quaternary treatment at larger plants on a defined timeline.
Robust secondary treatment is the foundation for micropollutant removal: quaternary processes such as ozonation or activated carbon work best on well-treated, low-solids effluent. Upgrading secondary treatment for stable performance is therefore a prerequisite before adding a quaternary stage.
Engineering Assessment
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