Quaternary treatment technologies: magnetic capture vs. activated carbon, ozone and membranes

Comparison criteria

Choosing a quaternary treatment technology requires weighing five criteria: removal efficiency (especially for microplastics and microfibres), operating cost (OPEX), initial investment (CAPEX), energy consumption, and waste generated. EU Directive 2024/3019 requires a minimum 80% reduction for a set of micropollutant indicators — any selected technology must guarantee this.

Powdered (PAC) and granular (GAC) activated carbon

Effective on dissolved compounds (pharmaceuticals, pesticides). Less effective for particles like microplastics — retention depends on the downstream filter. High OPEX: between €0.05 and €0.15 per m³treated. Generates solid waste requiring management (incineration or thermal regeneration). Moderate energy consumption.

Ozonation

Very effective at oxidising organic micropollutants. High energy consumption (0.3-0.6 kWh/m³) and risk of forming toxic by-products such as bromates — often requires an activated carbon post-treatment. Poorly effective at removing microplastics: it partially degrades them into even smaller fragments, which can be counterproductive.

Advanced membrane filtration

Ultrafiltration and nanofiltration retain virtually all microplastics and microfibres. Their weak point is fouling, which drives up operating costs and requires periodic chemical cleaning. Energy consumption 0.4-1 kWh/m³ and limited membrane lifespan.

Magnetic capture

Emerging technology — the one Plastikóre develops. Uses functionalised magnetic particles that selectively bind to microplastics and are recovered with magnetic fields, without aggressive chemical reagents and without membranes susceptible to fouling. Low energy consumption, reduced waste generation, and the possibility of recovering microplastics for study or specific management. Ideal as a complement or alternative to membrane filtration when the main target is microplastics and microfibres.

Comparison table

Recommendation by scenario

For urban WWTPs whose priority is removing microplastics and microfibres, magnetic capture offers the best CAPEX / OPEX / waste trade-off. For textile industrial effluents, it can be combined with filtration pre-treatment — see the article on microfibre filtration in the textile industry.