Removal of dissolved and colloidal matter from surface waters by composite flocculant aluminum salt-sodium alginate

Colloidal matter present in the surface water is an undesirable element that must be treated appropriately to make the water drinkable. The most commonly used process is coagulation-flocculation, followed by sand filtration to obtain excellent water quality with a turbidity limit value not exceeding 0.5 NTU. Despite the effectiveness obtained by this process, the reagents used poses problems in terms of their residual concentrations after treatment. This study focused on the removal of dissolved and colloidal matter from surface waters, used as a source for drinking water, by using a composite flocculant consisting of aluminum salt and sodium alginate. The tests were carried out on the waters taken from the Sidi Said Maachou dam located on the Oum Er-Rbia River in Morocco, whose turbidity was adjusted to 100 NTU and permanganate index of 7.16 mgO(2) L-1 that involved the organic matter. For the composite flocculant, tests showed 98% elimination of turbidity and 36% of organic substances for a dose of 4 mg L-1 of aluminum and 1.6 mg L-1 of sodium alginate. In contrast to the conventional method, it expends the aluminum six times more to achieve a reduction rate of 90% of turbidity and 28% of organic substances with a slight increase in conductivity. Several operating parameters were optimized to reduce the treatment cost.