Use of Power Plant Ash to Remove and Solidify Heavy Metals from a Metal-finishing Wastewater

Fongsatitkul, P.; Elefsiniotis, P.; Khuhasawan, N.; Jindal, R.

Use of Power Plant Ash to Remove and Solidify Heavy Metals from a Metal-finishing Wastewater

2009

Fongsatitkul, P. | Elefsiniotis, P. | Khuhasawan, N. | Jindal, R.

This laboratory-scale study investigated initially the potential of heavy metal removal from a metal-finishing wastewater using fly and bottom ash from a power plant as coagulants. It was found that the maximum heavy metal content in the ash-sludge mix was obtained at a fly ash-to-bottom ash ratio of 1.5:1 and a stirring time of 3 h, which resulted in heavy metal removal (i.e., Cr, Ni, Cu, Zn, Cd, and Pb) in excess of 99%, with effluent concentrations below the corresponding regulatory standards of Thailand. Furthermore, the feasibility of using fly ash as an admixture to stabilize and solidify the ash-sludge mix generated previously was explored. Results indicated that the stabilization/solidification process can achieve a high level of heavy metal removal efficiency from the ash-sludge mix. The optimum ratio regarding chromium leaching was found to be 1:0.75:0.75 (cement:fly ash:ash-sludge). In addition, the compressive strength and the chromium leaching concentration of the solidified sludge were within acceptable levels for secure landfill disposal and/or use as a construction material.

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