Assessment of groundwater contamination risk due to fly ash leaching using column study

Abstract

Fly ash contains various elements such as copper (Cu), cadmium (Cd), cobalt (Co), chromium (Cr), iron (Fe), manganese (Mn), sodium (Na), nickel (Ni), lead (Pb), zinc (Zn) potassium (K), and calcium (Ca) that may contaminate the surrounding environment due to leaching. In the present study, Open Column Percolation Test (OCPT) was used to understand the leaching behaviour of various elements from fly ash. The columns were filled with fly ash and underlying soil layer(s) of different particle size. The initial concentrations of different toxic elements for all combinations of column varied from BDL to 0.04 mg/L for Cu, BDL to 0.01 mg/L for Cd, BDL to 0.33 mg/L for Co, BDL to 0.01 mg/L for Cr, BDL to 1.10 mg/L for Fe, 0.32 to 2.23 mg/L for Mn, 0.06 to 0.71 mg/L for Ni, BDL to 0.17 mg/L for Pb, and 1.76 to 13.1 mg/L for Zn. Similarly, initial concentrations of ions ranged from 0.08 to 105.0 mg/L for Na, 2.0 to 87.80 mg/L for K, and 3.90 to 345.0 mg/L for Ca. The concentrations of most of the elements decreased with decreasing particle size and with increasing depth of the underlying soil layers. The study proposed an approach to find a suitable combination of different soil layers below fly ash with proper ratio of fly ash and soil layers to protect the leaching of elements from fly ash. This study will help to design suitable soil liners for safe disposal or utilization of fly ash.