Emergency water treatment with ferrate(VI) in response to natural disasters

The frequency and magnitude of natural disasters (e.g. hurricanes) have increased globally over the past century. Clean water is a top priority for disaster-affected populations. However, existing emergency water treatment (EWT) methods are not all feasible or technically effective in many emergency situations. The recent Puerto Rican water crisis after Hurricane Maria highlights the research needs and new challenges for new EWT technologies. In this study, bench scale experiments were carried out to evaluate ferrate(vi) for the treatment of simulated disaster-polluted water. Results show that ferrate(vi) treatment could simultaneously and effectively inactivate bacterial indicators, remove metal and metalloid contaminants, degrade dissolved organic matter, and reduce turbidity, while insignificantly increasing total dissolved solids (TDS) to ensure an acceptable TDS ≤ 1000 mg L^-1 (the recommended minimum TDS standard for an emergency water supply). The ferrate(vi) dose played a key role, because it directly influenced the removal efficiencies and also affected the size distributions of iron and metal/metalloid contaminants after treatment. As the ferrate(vi) dose increased, the fractions of soluble and colloidal iron and metal/metalloid contaminants decreased, while their particulate portions increased, implying that the contaminants were associated with ferrate(vi) resultant iron particles. Therefore, an increased ferrate(vi) dose could accelerate the aggregation of fine iron particles, thereby facilitating the removal of associated toxic metals and metalloids in ensuing solid-liquid separation. Ferrate(vi) opens a new opportunity for EWT to provide safe and sufficient water for disaster-affected populations and rapid disaster relief. The knowledge can also be applied to ferrate(vi) treatment design for municipal water treatment and reuse, supporting urban water sustainability.