Heavy metal contamination and health risk assessment in waste mine water dewatering using phosphate beneficiation processes in Jordan

Abstract

Phosphate production is one of the major industries in Jordan. Phosphate beneficiation processing consume large quantities of its limited fresh water resources for processes such as washing and flotation. The process of mine water effluents have long been contained with remarkably high levels of heavy metals (e.g., Cd, Cr, Mn, Mo, Ni, Pb, U, V, and Zn), making them toxic for human health and surrounding environemnt. The main objective of this study was to determine the heavy metal contamination in washing mine water of phosphate bed-A1 (WMW-A1) and flotation mine water of phosphate bed-A3 (FMW-A3) of a Jordan phosphate mine (Eshidiya), to assess the health risks associated with oral daily intake and dermal absorption of mine water effluents from phosphate mining process. The results indicated accumulations of Cd, Cr, Li, Mn, Mo, Ni, Pb, U, V, and Zn in the mine water, with lower concentrations than the Jordan standards for discharge of water bodies into streams. In particular, Mn and Cr exhibited high levels of pollution in mine water due to their slightly higher contamination index values (CI). This can be interpreted to variation in geochemical behavior of these metal contents naturally present in francolite mineral phase. Varimax rotated factor analysis, cluster analysis, and correlation analysis revealed that Cd, Cr, Li, Mn, Mo, Ni, Pb, U, V, and Zn in mine water were mainly related to geochemical behavior for francolite mineral phase and clay mineral phase represents the main source of mine water contamination. The hazard quotient (HQ) and hazard index (HI) values were assessed to determine health risk (e.g., non-carcinogenic risk and cancer risk) in case of daily intake and dermal exposure pathways in mine water. The health risk assessment showed that As, Hg, Ni, Pb, and Zn are < 1, indicating non-carcinogenic risk tends to become significant for daily intake and dermal exposure pathways by the mine water. The cancer risk of being exposed to lead through WMW-A1 and FMW-A3 from these sources did not exceed the acceptable risk limits of 1:10,000 for regulatory purposes. Overall, this study provides comparative research on the accumulation, potential health risks and sources of heavy metals in mine water (washing and flotation) beneficiation process in Eshidiya mines, and our findings suggest that, Mn and Cr in both mine water could potentially represent environmental problems.