COAGULATION-FLOCCULATION AS TERTIARY-TREATMENT OF EFFLUENTS FROM DEEPWASTE-WATER STABILIZATION PONDS

A physicochemical coagulation- flocculation treatment was applied to t he effluent of a deep stabilization pond in order to reduce its suspen ded solids and, thus, its suspended and colloidal organic matter conte nt. Total Organic Carbon (TOC) was used to quantify the organic matter content since it can be measured rapidly and with a high degree of re producibility. The coagulants used in the experiments were: Fe-2(SO4)( 3), FeSO4 . 7H(2)O and Al-2(SO4)(3) . 18H(2)O. The efficiency of the p rocess was studied as a function of coagulant dose, pH and sedimentati on time. In optimal conditions, TOC elimination reached 80% for Fe-2(S O4)(3), 60% for FeSO4 . 7H(2)O and 60% for Al-2(SO4)(3) . 18H(2)O. The most probable explanation of the coagulation phenomenon in the pH con ditions of the experiment is that the colloidal matter was immersed an d then precipitated in a ''sweep floc'' of Fe(OH)(3) or Al(OH)(3).