Strategies for alkalinity and pH control for ozonated shrimp pond water

Abstract

In order to derive the full benefits of ozonation technology for the destruction of toxic metabolites in shrimp grow-out ponds, strategies to supplement and control high alkalinity loss during ammonia oxidation in a model ozonation system were studied. Alkalinity loss and pH profiles were investigated in the ozonated model system containing artificial seawater and ammonia, and alkalinity compensation ability of supplements such as calcium carbonate-based limes, hydrated limes and sodium bicarbonate were evaluated. In some experiments, application of these supplements during ozonation were combined with other treatments like recarbonation (external CO2 supply). Results showed that calcium carbonate-based limes were not anymore effective for alkalinity supplementation when ozonation is applied to seawater containing ammonia. Although recarbonation improved the effectiveness of CaCO3 as an alkalinity supplement, application in large ozonated grow-out ponds were considered not practical. The effective alkalinity supplements for ozonated seawater containing ammonia were the more soluble materials, high purity sodium bicarbonate and hydrated lime applied at a proper dosage. Sodium bicarbonate and hydrated lime would be more appropriate alkalinity control strategies for in situ1Ozonation inside grow-out pond.1 ozonated shrimp grow-out ponds; however, for application of hydrated lime, the problem of overdosage should be taken into consideration.