Dye discharges are problematic from both environmental and esthetic point of view. The legislation in force, the increasing environmental awareness, and the widening range of dyes available on the market have prompted us to look for the most efficient wastewater treatment possible. Adsorption and membrane filtration have proven as efficient wastewater treatment measures. The best-known and the most often used adsorbent is activated carbon, characterized by great specific surface area. One of the main advantages of membrane processes is that concentration and separation can be obtained without any changes in physical state and without the use of either chemicals or thermal energy. The present thesis aims at finding an alternative to the costly use of activated carbon, by utilizing recycled waste material from the environment, which is characterized by low price, easy accessibility, and specific adsorption characteristics. Six different adsorbents were used, i.e. coarse and fine sawdust obtained from a local carpenter, sludge biomass from the central wastewater treatment plant in Ljubljana, an adsorbent made by ourselves from grill charcoal, powdered activated carbon produced by Merck, and waste ashes from the thermal power and heating plant in Ljubljana. We measured the changes in colorization and concentration of the coloring solution ensuing from the use of various adsorbents, varying quantities of adsorbents, and different contact times.