Nitrate (NO3-) is a common groundwater contaminant in the United States, primarily as a result of its widespread use in agriculture as fertilizer.  The US EPA regulates nitrate levels in drinking water, due to negative health effects in infants and pregnant women.  Ion exchange (IX) systems are proven to efficiently remove nitrate from drinking water, but the disposal of waste brine produced during IX flushing and regeneration is expensive and has a negative environmental impact (both in terms of salt production and disposal of the waste brine itself).  Reduction of NO3- to N2 in the waste brine would enable brine reuse in multiple resin regeneration cycles, decreasing process costs and environmental impacts.  Catalytic treatment of waste IX brine is currently being investigated as a potential method for brine treatment.  Bimetallic palladium-indium catalysts immobilized on an activated carbon support (Pd-In/AC) show promising results in bench scale batch and column reactors for nitrate reduction and brine treatment.  The main objectives of this presentation are to present results from: a) batch testing to determine the most efficient metal loadings, b) two different flow-through column studies to determine catalyst activity and deactivation, c) batch and column studies determining effective alternative treatments to reverse catalyst deactivation.  Additionally, the presentation will discuss the hydrogen mass transfer limitations related to the current laboratory column configuration and the impact of design changes.  The benefits and challenges of using catalytic treatment for brine reuse in IX resins will also be summarized.

Bimetallic palladium-indium catalysts for treatment of nitrate in waste ion exchange brines

246th National Meeting (2013)

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