In chemistry, oxidation describes the process of combining or becoming combined with oxygen. Oxidation can take place chemically or it can be catalysed by a microbial process (by bacteria). In wastewater treatment, oxidation means when bacteria oxidise organic loads in the wastewater in a fast single step process leading to the production of CO2 and heat. The process rate increases along with increasing temperature. Examples of application of oxidation are Trickling Filters, Rotating Biological Contactors, Aerobic Ponds, Aerated ponds, Activated sludge, etc.