Efficiency of active carbon applied in water treatment technologies depends on selection of a proper adsorbent, but also on methods and conditions of its use. These subjects are discussed taking as a model example the sorption of phenol on different, also chemically modified (HNO
, ozone) and biological activated carbons. Ozonation of active carbon changes its porous structure and in the case of phenol it reduces its sorptivity. Strong oxidation of the active carbon with HNO
, affects also kinetic parameters of the sorption process (the effective diffusion coefficient decreases). The application of biologically active carbon offers wide opportunities. A combination of sorption and biodegradation processes enables advanced removal of phenol from the solution on the one hand, and on the other hand it binds this toxic substance before direct exposure to microorganisms.