This thesis is focused on two environmental issues. The first one is the recovery of different wastes, such as sewage sludge and fly ashes, and the second one is related to the removal of odour causing compounds which are generated in the same waste water treatment plant (WWTP), like NH3 and H2S. Direct alkaline activation with NaOH and KOH of two sludges which have different specific treatments in the sewage sludge line, has been studied, and it has been compared with the activation of their chars. Two different heating mechanisms were applied: conventional heating and microwave oven heating. All the sewage sludge-derived materials are tested for NH3 removal adsorption experiments. On the other hand it has been studied the preparation of adsorbents by mixing on sewage sludge with fly ashes heated in a microwave oven. The materials adsorbents have a limited development of porosity and are tested for H2S removal.