The European Directive 2024/3019 concerning urban wastewater treatment stipulates the extension of many existing wastewater treatment plants over the course of the next two decades to include a 4^th treatment stage to remove micropollutants like pharmaceuticals, cosmetics, and microplastics.

Common solutions for micropollutant removal in a quaternary treatment stage are ozonation, activated coal adsorption, and combinations of the two in series. The adoption of such treatment stages is associated with considerable investment and operational costs.

This paper presents a precoat filtration application that incorporates powdered activated carbon in a cellulose layer that removes micropollutants from the effluent streams of wastewater treatment plants. A pilot plant was installed at the Steinhof wastewater treatment plant in Braunschweig and operated for three months in continuous operation. Prior to stable operation, many obstacles had to be overcome, including blinding of the filter discs with cellulose and organic materials, the full conversion of an apparatus normally used in oil filtration to the use in slightly acidic wastewater, and difficulties in the dosing of the filter aid.

Scale-up operations to a fully working pilot-sized filtration plant are presented as well as measurements regarding discharge levels of micropollutants as specified in the European directive. The precoat filter is best suited for small wastewater treatment plants – plants from 10.000 population equivalents will need to introduce a quaternary treatment stage if situated in regions where runoff poses environmental or public health risks – and industrial plants that either have direct discharge or that may be prohibited from discharge into the urban wastewater streams in the future.