A method of treating sewage and wastewater through microbial oxidation. Sewage previously treated in settling tanks is aerated to encourage the growth of nonpathogenic aerobic microorganisms (bacteria, yeasts, molds and protozoans) which break the organic matter down into carbon dioxide, water, and simple salts. After this activated sludge is produced, the wastewater undergoes further processing through anaerobic digestion, filtering, and chlorination.