The Hydraulic Performance of Waste Stabilization Ponds in Portugal

The hydraulic regime in two Portuguese facultative waste stabilization ponds, a primary facultative pond receiving raw sewage (in Portimão) and a secondary pond receiving the effluent from an anaerobic pond (in Vidigueira) was studied by means of a fluorescent dye tracer technique. The resulting dispersion numbers, respectively for winter and summer, for each pond were as follows: 0.595 and 0.371 in Portimão, and 0.574 and 0.523 in Vidigueira. These results did not agree with those obtained from the available predictive equations in the recent literature.