The stabilization of organic matter in sewage wastes requires oxygen, which in secondary treatment plants is normally obtained from the atmosphere. The primary source of atmospheric oxygen is photosynthesis, for which the sun supplies the energy and water supplies the oxygen. Sewage contains the necessary nutrients for photosynthetic organisms to produce oxygen and at the same time to fix these valuable nutrients as well as solar energy in reclaimable material. Laboratory and pilot-plant investigations of sewage treatment in open ponds by photosynthetically produced oxygen have been conducted during the years 1951-1955. These studies have provided some basic principles which can be utilized for the engineering design of the process as well as for the prediction of the operational performance of new or existing oxidation ponds. In this paper the authors have formulated design criteria based on these principles. The chemical, biological, operational, and economic factors that affect the use of engineered photosynthesis as a method for producing oxygen and reclaimable wastes are outlined.