Stormwater treatment – Sorption of organic biocides from paints and renders

Sammanfattning: In recent years, the fact that stormwater is not as clean as previously assumed have been addressed. A variety of chemicals have been pointed out as more problematic than others. This report will focus on organic biocides found in paints, renders and flat roofs in an urban milieu. It will aim to assess sorption as a local treatment method and to develop and test a model for source identification. As a way of reducing analysis costs Disperse Black 2, an azo-dye, with similar physiochemical properties as the biocides which can be detected using a spectrophotometer, was used as a substitute. Adsorption batch tests were carried out using powdered activated carbon (PAC) and vermiculite. Adsorption isotherms were analyzed to establish adsorption mechanisms and the general adsorption efficiency was assessed both for the substitute and for the biocides. PAC was found to efficiently remove Disperse Black 2 (94% at 0.24 g PAC L-1) as well as the biocides (>99% at 0.24 g PAC L-1). The vermiculite had a lower efficiency for both Disperse Black 2 (19% at 0.24 g vermiculite L-1) and the biocides (83-91% at 0.3 g vermiculite L-1)but is a cheaper material to use.