Chemical Weathering in a Hypersaline Effluent Irrigated Dry Ash Dump: An Insight from Physicochemical and Mineralogical Analysis of Drilled Cores

M.W. Gitari, L.F. Petrik, K. Reynolds


Accumulation of high ionic strength effluents (brines) that require disposal in inland industries where water recycling is necessary due to scarcity is a major challenge. A coal combustion power utility in South Africa utilizing a dry ash disposal system produces 1.765 Mt of fly ash per annum and also employs the zero liquid effluent discharge policy (ZLED) to manage its liquid effluents. Fly ash is conditioned for dust suppression before being conveyed to the ash dumps with the high saline effluent. The saline effluents results from various processes employed for maximum utilization, upgrading and re-use of various mine water and industrial effluents such as RO, EDR, softening and ion exchange in an effort to adhere to ZLED policy. In the ash dumps it is further conditioned by irrigation with the high saline effluents, therefore the ash acts as a repository for the salts. This study is an attempt to understand the chemical weathering of the effluent conditioned fly ash and species mobility in a dry disposal scenario. A combination of leaching tests was performed for fresh ash and drilled cores to estimate the highly leachable species. Results from DIN-S4 tests of the fresh and weathered ash reveal that Ca, K, Na, Mg, Ba, SO42-, Se, Mo and Cr are highly leached. Leaching tests also revealed that major soluble components in the solution at equilibrium are Ca, Na, SO42- and K. Weathering profiles of the ash dump cores were observed to follow a similar trend. The greatest weathering was observed to take place at the top layer (0.55-3 m depth) in the weathered ash cores (15 years and older), showing that infiltration of rain water over time has a profound effect on the decrease of the pore water pH.  Analysis of the extracted pore water in each of the different weathered ash cores by depth indicated the mobility of several elements through the ash. Increased cation exchange capacity at 4-5 m depth suggests a transient mineralization zone.

Key words:  Weathered fly ash; Pore water; Ash dumps; Hypersaline effluents; X-ray diffraction analysis; DIN-S4 test; Cation exchange capacity


Key words: Weathered fly ash; Pore water; Ash dumps; Hypersaline effluents; X-ray diffraction analysis; DIN-S4 test; Cation exchange capacity

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[1] He, F., & Qin, D. (2006). China's Energy Strategy in the Twenty-First Century. China and World Economy, 14, 93-104.

[2] Klass, L.D. (2003). A Critical Assessment of Renewable Energy Usage in the USA. Energy Policy, 31, 353-367.

[3] Willis, J. P. (1987). Variations in the Composition of South African Fly Ash, Ash - a Valuable Resource. Council for Science and Industrial Research, 3, 2-6.

[4] Petrik L., White, R., Klink, M., Somerset, V., Key, D.L., Iwuoha, E., Burgers C., & Fey, M.V. (2005). Utilization of Fly Ash for Acid Mine Drainage Remediation. WRC Report No. 1242/1/05, South Africa.

[5] American Society for Testing and Materials (1993). ASTM 618: Standard Speciation for Fly Ash and Raw or Calcined Natural Pozzolan for Uses as a Mineral Admixture in Portland Cement Concrete. Philadelphia, Pennsylvania: American Society for Testing and Materials.

[6] Adriano, D.C., Page, A.L., Elseewi, A.A., Chang, A.C., & Straughan, I. (1980). Utilization and Disposal of Fly Ash and Other Coal Residues in Terrestial Ecosystems: A Review. J. Environ. Qual., 9 (3).

[7] Early, L.E., Rai., D., Mattigod, S.V., & Ainsworth, C.C. (1990). Geochemical Factors Controlling the Mobilization of Inorganic Constituents from Fossil Fuel Combustion Residues: Ⅱ. Review of the Minor Elements. J. Environ. Qual., 19, 202-214.

[8] Mattigod, S.V., Dhanpat, R., Eary, L.E., & Ainsworth, C.C. (1990). Geochemical Factors Controlling the Mobilisation of Inorganic Constituents from Fossil Fuel Combustion Residues: Ⅰ. Review of the Major Elements. Journal of environmental quality, 19,188-201.

[9] Gitari, M.W., Petrik, L.F., Etchebers, O., Key, D.L., Iwuoha, E., & Okujeni, C. (2006). Treatment of Acid Mine Drainage with Fly Ash: Removal of Major Contaminants and Trace Elements. Journal of Environmental Science and Health Part A, 41, 1729–1747.

[10] Gitari, Wilson M., Fatoba, Ojo, O., Petrik, Leslie F., & Vadapalli, Viswanath R. K. (2009a). 'Leaching Characteristics of Selected South African Fly Ashes: Effect of pH on the Release of Major and Trace Species. Journal of Environmental Science and Health, Part A, 44, 206 -220

[11] Gitari, M W., Fatoba, O O., Nyamihingura, A., Petrik, L F., Vadapalli, V R K.., Nel, J., October, A., Dlamini, L., Gericke, G., & Mahlaba, JS. (2009b). Chemical Weathering in a Dry Ash Dump: An Insight from Physicochemical and Mineralogical Analysis of Drilled Cores. World of Coal Ash Conference, May, 4-7.

[12] Muriithi Grace, Nyambura., Gitari Wilson Mugera., Petrik Leslie Felicia., & Ndungu Patrick Gathura. (2011). Carbonation of Brine Impacted Fractionated Coal Fly Ash: Implications for CO2 Sequestration. Journal of Environmental Management, 92, 655-664.

[13] Jackson, B.P., & Miller, W.P. (1998). Arsenic and Selenium Speciation in Coal Fly Ash Extracts by Ion Chromatography-Inductively Coupled Plasma Mass Spectrometry. Journal of Analytical Atomic Spectrometry, 13, 1107-1112.

[14] DIN 38414 S4 (1984). German Standard Procedure for Water, Wastewater, and Sediment Testing-Group S (Sludge and Sediment), Determination of Leachability (S4). Berlin, Germany: Institut fur Normung.

[15] Eckert, D.J. (1988). Recommended pH and Lime Requirement Tests. P 6-8. In W.C. Dahnke (ed), Recommended chemical soil test procedures for the North Central Region, North Dakota Agri. Expt. Sta. Bulletin No. 499 (Revised).

[16] Chapman, H. D. (1965). Cation Exchange Capacity. In Methods of Soil Analysis (Edited by Black, C. A.) (Part 2, pp. 891-901). Madison, Wisconsin: Am. Inst. Agronomy.

[17] Choi, S.-K., Lee, S., Song, Y.-K., & Moon, H.-S. (2002). Leaching Characteristics of Selected Korean Fly Ashes and Its Implications for the Groundwater Composition near the Ash Disposal Mound. Fuel, 81, 1083-1090.

[18] Zevenbergen, C., Vander Wood, T., Bradley, J.P., Van der Broeck, P.F.C.W., Orbons, A.J., & Van Reeuwijk, L.P. (1994). Morphological and Chemical Properties of MSWI Bottom Ash with Respect to the Glassy Constituents. Hazard. Waste Hazard. Mater, 11, 371–383.




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