Physico-chemical treatment of Merida landfill leachate for chemical oxygen demand reduction by coagulation

Abstract

In order to determine the optimal dosage and type of coagulant for the physico-chemical treatment of leachate from the sanitary landfill of Merida, Mexico, a total of 864 jar tests were performed. Four metallic coagulants (ferric chloride, ferric sulphate, aluminium polychloride and aluminium sulphate) with doses ranging between 50 and 300 mg L^-1 and two polyelectrolytes (high-density anionic and cationic reagents) with doses from 2 to 12 mg L^-1 were tested. Neither an adequate type of coagulant nor an optimal dose could be found. The removal of contaminants was measured as total and dissolved chemical oxygen demand (COD). Soluble COD removal efficiencies were low, from 0 to 47%, with a 4% average value only. These low values of organic material removal were attributed to the particular characteristics of the Merida landfill leachate (low suspended solids concentration), so even with sweep-floc coagulation (300 mg L^-1 dose) only low COD removal efficiencies were obtained. A study of the suspended particle size distribution of the leachate was conducted in order to explain the poor performance. The particle size distribution ranged from 0.375 to 948.2 μm, with an average value of 22.97 μm. In a second step the optimal pH for physico-chemical treatment of these leachates was determined. Finally a greater than 90% removal of organic material, measured as suspended COD, was obtained at pH 2, which was considered as the optimal value.

Keywords

coagulation-flocculation leachate treatment particle size Merida landfill physico-chemical treatment COD reduction wmr 750-4

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References

Al Yaqout, A.F. (2003) Assessment and analysis of industrial liquid waste and sludge disposal at unlined landfill sites in arid climate . Waste Management 3 (9), 817-824 .

APHA , AWWA & WEF (1998) Standard Methods for the Examination of Water and Waste Water, 20th edition, APHA, AWWA & WEF, Washington DC .

Chofqi, A. , Younsi, A. , Lhadi, E. K. , Mania, J. , Mundry, J. & Veron A. (2004) Environmental impact of an urban landfill on a coastal aquifer (El Jadida, Morocco) . Journal of African Herat Sciences 39, 509-516 .

Duran, P., Ramírez, Z. & Durán, M. (2002) Bioadsorción de lixiviados viejos clarificados. In: Memorias del XIII Congreso Nacional de la FEMISCA, pp. 455-460, Morelia, Mexico.

Jensen, D. & Christensen, T. (1999) Colloidal and dissolved metals in leachates from four Danish landfills . Water Residual, 33(9), 2139-2147 .

Lu, J. , Eichenberger, B. & Stearns, R. (1985) Leachate from municipal landfills production and management , Pollution Technology Review, 119, 144-156 .

Marttinen, S. , Kettunen, R. & Rintala, J. (2002) Occurrence and removal of organic pollutants in sewages and landfill leachates . The Science of the Total Environtment, 301, 1-12 .

Tatsi, A. , Zouboulis, A. , Matis, K. & Samaras, P. (2003) Coagulatión - floculation pretreatment of sanitary landfill leachates . Chemospere, 53, 737-744 .

Tchobanoglous, G. , Theisen, H. & Vigil, S. (1993) Integrated Solid Waste Management. Engineering Principles and Management Issues. McGraw-Hill International Editions. Singapore .