The potential of bacterial photosynthesis in recycling of human wastes

(1) Potential uses of photosynthetie bacteria in the recycling of human wastes have been considered. I t is concluded that systems using photosynthetic bacteria may have advantages over purely algal systems under conditions where total recycling is needed and energy is not abundant. (2) Two systems are proposed in which the metabolic potential of the photosynthetic bacteria might be realized. Both systems include an anaerobic recycling stage in which fer­ mented wastes are converted to biomass by bacterial photosynthesis. In one system gaseous recycling is accomplished by a secondary algal reactor acting under aerobic conditions. In the other, oxygen is regenerated by electrolysis of water, and hydrogen and carbon dioxide are assimilated autotrophically under anaerobic conditions in the same bacterial photosynthesis reactor used for anaerobic recycling. (3) Advantages and disadvantages arising from the use of photosynthetic bacteria in re­ cycling are discussed, and some potential model systems are proposed.