Cactus Opuntia as natural flocculant for urban wastewater treatment.

The cactus tree, species Opuntia ficus-indica, is a primary material of many products in various domains such as cosmetics, medicine and nutrition. In the present work, we assess its potential as a flocculant. We tried a technique which adopts three sequential treatments that used coagulation, flocculation and sedimentation processes under certain operating conditions. For this purpose, we used the aluminum sulfate (AS) as coagulant and fresh cladodes juice (FCJ) as bioflocculant. All tests were carried out on high turbid urban wastewater collected from the Metlaoui's Wastewater Treatment Plant (MWTP) (in Gafsa in southwest Tunisia). Experiments with this couple AS/FCJ show very interesting results: a high-removal of turbidity (TUR), suspended solids (SS) and chemical oxygen demand (COD). The percentages of abatement of these parameters are respectively 93.65%, 82.75% and 64.30%. The experimental results of the present study prove that the turbidity, SS and COD removal efficiency of new technique is superior to that of conventional process (with only AS). By this technique, we save 50% in AS dose. Moreover, flocs formed by the treatment using AS/FCJ are coarse and readily settleable.