Effect of fish management on fecal coliform removal in facultative ponds

Abstract

The effect of fish, of the genus Tilapia, on fecal coliform removal in a batch reactor with water from a facultative pond was analyzed. The bacterial mortality constant decreased proportionally as the number of fish increased. lt was concluded that the number of fish influences the efficiency of pathogen removal in facultative and maturation ponds by reducing the fecal coliform removal rate. Prior studies indicated that one of the principal factors in bacterial removal is a pH above 8.5. ln this study, a pH of up to 9.9 was obtained in the control reactors where, as there was no depredation of algae by fish, a greater decrease in bacteria was observed. Based on this observation, and contrary to suggestions in the literature, the use of fish is not recommended in facultative and maturation ponds, but rather in the tanks following treatment when the design removal efficiencies have been obtained. This will result in a lower effluent BOD, product of the algae, and contribute to compliance with standards. lt will also prevent the need to dispose of the sludge, and will reduce the photosynthesis and oxygen production required for the self-purification process.