High-rate pond for treatment of piggery wastes

This work deals with studies on high-rate ponds, a batch working system that is followed by a filter pond where Chinese carp were introduced for piggery wastes treatment. COD removal values for the high-rate pond were in the order of 95% in the summer and 70% in the winter for an initial concentration of 2000 mg/L. Total nitrogen removal values ranged between 90% and 60%, respectively, in summer and winter periods for an initial concentration of 600 mg/L. Seasonal variations, which are mainly observed under differences of temperature, were shown to be not relevant for total phosphorus removal, a process that appears to depend mainly on increases of pH values over 8.5. An hydraulic retention time ranging between 15 to 20 days was found to be best for pond functioning. The plug flow model fits well to the pond's physical characteristics. The filter pond was shown to be a great potential process for removal of algae produced in the high-rate pond.