Heavy metals in drinking water pose a threat to human health. Populations are exposed to heavy metals primarily through water consumption, but few heavy metals can bioaccumulate in the human body (e.g., in lipids and the gastrointestinal system) and may induce cancer and other risks. To date, few thousand publications have reported various aspects of heavy metals in drinking water, including the types and quantities of metals in drinking water, their sources, factors affecting their concentrations at exposure points, human exposure, potential risks, and their removal from drinking water. Many developing countries are faced with the challenge of reducing human exposure to heavy metals, mainly due to their limited economic capacities to use advanced technologies for heavy metal removal. This paper aims to review the state of research on heavy metals in drinking water in developing countries; understand their types and variability, sources, exposure, possible health effects, and removal; and analyze the factors contributing to heavy metals in drinking water. This study identifies the current challenges in developing countries, and future research needs to reduce the levels of heavy metals in drinking water.
This research work investigates the iron chromatographic displacement from the granular activated carbon (GAC) columns that occurred in the Vars, Ontario groundwater treatment plant. Natural organic matter (NOM) (XAD-8) fractionation showed that 30% of NOM was hydrophobic with the capability of forming complexes with iron. CHELEX-100 isolation indicated that 37–40% of the iron was organically-bound. The quantification of complexed iron performed on GAC microcolumn effluent at iron exhaustion point showed that this iron was neither adsorbed nor split from NOM. This indicates that NOM–iron complexes were not the cause of the observed chromatographic displacement of iron and suggests that competitive adsorption between iron and NOM forced the previously adsorbed iron to be desorbed. Adding greensand treatment prior to the GAC columns resulted in full iron removal, which suggests that NOM–iron complexes must have been either broken by potassium permanganate oxidation and/or adsorbed by the greensand filter.
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