Hydrodynamics of a medium scale depuration system for bivalve mollusks with hydraulic detention time distribution experiment

Abstract

The determination of the residence time distribution function and the test with tracers can be used to describe the hydrodynamic behavior of a vessel. It is possible to assess whether the water is well distributed within a tank, or whether there are short-circuits and dead zones. This technique was applied to evaluate if the hydrodynamics of a mollusk purification tank, built outside the recommended specifications, provides a good distribution and renewal of water within its volume. Salt water was used as a tracer in a step tracer experiment. The salt concentration was measured continuously at different points inside tank. The result for the average residence time was 33 minutes, close to the theoretical value and the volumetric efficiency of the tank is practically equal to 1. The results indicate that the entire volume of the tank was used and that the water is well distributed with low occurrence of short-circuits or dead zones. The system also showed the ability to maintain an adequate dissolved oxygen concentration and temperature. The technique used in this study can be used to evaluate tanks built outside the international recommendations or presenting performance.