Damage control: Managing the residuals generated during arsenic treatment

The recently reduced USEPA Maximum Contaminant Level (MCL) for arsenic in drinking water has forced facilities to either implement new or modifying existing arsenic removal technologies to meet the 10 μg/L MCL. The favored EPA-identified treatment option is adsorption onto solid media. These treatment processes generate arsenic-bearing solid residuals (ABSR) that must be tested and potentially treated prior to disposal. A growing body of research has demonstrated that these residuals may pose an unacceptable risk if disposed untreated in non-hazardous landfills. This risk motivated the development of an innovative stabilization method: polymeric encapsulation. Polymeric encapsulation out-performs the only reported alternative encapsulation technique, cement stabilization, with respect to both residual loading capacity (greater than 3-fold increase) and leach resistance. Another way to reduce the risk of ABSR disposal is to reduce the amount of ABSR generated, which could be achieved through the use of regenerable media. However, regeneration produces an arsenic-laden brine that must then be treated prior to disposal. This research investigated the use of less common, non-iron-based adsorption media for the treatment regenerate brine waste streams. Four media types (lanthanum hydroxide, ferric/lanthanum hydroxide, zirconium dioxide, and titanium oxide composition) were identified as potential treatment options based on their ability to retain relatively high arsenic capacities relative to traditional iron-based media.