A RATIONAL APPROACH TO THE DESIGN OF WASTE-WATER-FED FISHPONDS

A procedure is given for the minimal treatment of wastewater in a 1-da y anaerobic pond followed by a 5-day facultative pond prior to dischar ge into a fishpond. The criterion for the design of the fishpond is a surface loading of total nitrogen of 4 kg N ha-1 d-1. The number of fa ecal coliforms in the fishpond is then determined; this should be not greater than 1000 per 100 ml to ensure that the fish are microbiologic ally safe for human consumption. Fish (carp and tilapia) yields are of the order of 13 t ha-1 a-1, assuming that the pond is drained and har vested three times a year and that there is a fish loss of 25 percent. Preliminary financial analysis indicates that such a wastewater-fed f ishpond system is commercially viable.