Fig. 4.

Sorption of surfactants (square—□ – cationic, diamond—◊ - anionic, circle—○ – non-ionic; initial concentration of 10 mg/Ll) after short- term exposure (< 1 min) to activated sludge biomass at different concentrations (expressed as g of dry matter per literlitre, ranging from 0.05 to 6).