TREATMENT OF WASTE-WATER BY STABILIZATION PONDS - APPLICATION TO TUNISIAN CONDITIONS

An experimental study of the domestic wastewater treatment in a series of four pilot-scale stabilization ponds was conducted. The objective was to adapt the treatment by waste stabilization ponds (WSP) to Tunis ian conditions. The obtained results show that the average values of r emoval are about 72% for BOD, 65% for COD and more than 50% for ammoni a nitrogen. The phosphate concentration was influenced by release of p hosphate from decomposition sediment The elimination of total coliform , faecal coliform and faecal streptococci is between 99.3% and 99.99%. The most rate reduction was registered during the warm months which c oincide with the irrigation season. The sediment accumulation is taken mainly in the first pond: the deposition rate is high (5 cm/year). In the three maturation ponds, it ranges from 1.3 to 1.6 cm/year. The WS P can be designed to satisfy Tunisian conditions. Because of favourabl e climate, loading can be much higher than those reported in the liter ature and some of the disadvantages of the pond system can be reduced. So we can economize in evaporation of effluent which is considered as a resource of irrigation in agriculture and we can reduce the surface area.