Note
Oxidation ponds have been used for many years for treatment of domestic wastewater. Nutrients and carbon dioxide produced by the decomposing organic wastes enhance the growth of unicellular algae which, in turn, provide oxygen for the bacterial decomposition. When such ponds have an effluent, however, the algae themselves represent a loading of organic matter that fails to meet discharge standards, so the algae must be removed from the water. Conventional harvest techniques are uneconomical, particularly in view of the low value of the product.