6 - Biological oxidation of organic matter

Abstract

Many of the problems associated with water quality control are due to the presence of organic matter from natural sources or from wastewater discharges. This organic matter is normally stabilized biologically and the microorganisms involved utilize either aerobic or anaerobic oxidation systems. In the presence of oxygen, aerobic oxidation takes place, in which part of the organic matter is synthesized to form new microorganisms and the remainder is converted to relatively stable end products. In the absence of oxygen, anaerobic oxidation produces new cells and unstable end products such as organic acids, alcohols, ketones, and methane. The anaerobic methane-producing system which is used in wastewater treatment takes place in two stages. In the first stage acid-forming microorganisms convert the organic matter into new cells and organic acids and alcohols. A second group of microorganisms, the methane bacteria, then continue the oxidation, again utilizing part of the organic matter to synthesize new cells and converting the remainder to methane, carbon dioxide, and hydrogen sulfide.