Processing of Phosphate Mine Tailings by Coagulation Flocculation to Reduce Marine Pollution in Togo: Laboratory Tests

• Published in: Mine water and the environment 2005-12, Vol.24 (4), p.215-221
• Main Authors: Gnandi, K., Tchangbedji, G., Killi, K., Baba, G., Ouro Salim, A. I.
• Format: Article
• Language: English
• Subjects: Cadmium; Chromium; Coagulants; Coagulation; Coastal waters; Copper; Flocculation; Iron; Jar tests; Laboratory tests; Lead; Marine pollution; Mine tailings; Mine wastes; Phosphates; Phosphorite; Pollution control; Sea pollution; Sludge; Tailings; Trace metals; Turbidity; Water treatment; Zinc
• ISSN: 1025-9112; 1616-1068
• DOI: 10.1007/s10230-005-0102-2

AbstractAbout 2.5 million t of sedimentary phosphorite mine tailings, highly enriched with trace metals such as Cd, Cr, Cu, Ni, and Zn, are dumped annually in the coastal waters of Togo without any pre-treatment, causing serious pollution problems in the region. We conducted laboratory jar tests of a coagulation-flocculation procedure with coagulants RM45U and AN945MPM to clarify the sludge. The efficiency of the method depends particularly on two factors: the amount of coagulant and the solid concentration of the sludge to be treated. Thus, with a mud concentration of 47.7 g/L, the average optimal amount of the two coagulants was 25 mg/L. With both coagulants, water turbidity passed from 60 x 103 NTU to approximately 3 NTU after clarification with the optimal amount of the two coagulants. RM45U reduced concentrations of Pb by 40%, Zn by 98.8%, Fe by 80.6%, and Cd by 32.8%. AN945MPM reduced Pb by 20%, Zn by 98.5%, Fe by 48%, and Cd by 32.8%.