Biological removal of nitrate with arsenic adsorption

Nitrate, arsenic and vanadium are all potential groundwater contaminants. Various resource constraints can make conventional treatment methodologies, such as ion exchange and membrane processing, challenging to implement for small utilities. This research examined the potential of biological denitrification withParacoccus denitrificans and adsorption to ferric hydroxide precipitates to simultaneously remove nitrate and either arsenic or vanadium. Continuous bench-scale testing found that average nitrate removal of up to 60% was obtained. The continuous bench-scale testing also found that arsenic and vanadium were both removed by way of adsorption to ferric hydroxide precipitates. The average per cent removal for arsenic and vanadium were 81·5% and 91·1% when 2 mg/L of iron was added. In fact, arsenic concentrations were below 10 μg/L following addition of 2 mg/L of iron. This bench-scale system demonstrates the potential of integrating bio-adsorption for co-contaminant removal, which could hold promise for small communities requiring an innovative approach to simultaneously remove contaminants.