IN SITU DESTRUCTION OF NITRATE AND NITRITE IN CONTAMINATED GROUNDWATER: APPLICATION OF A CATALYST REACTOR BED

Bench scale laboratory experiments were conducted to evaluate the efficiency of Palladium (Pd) catalysts to treat nitrate and nitrite present in the contaminated groundwater. Application of fixed-bed reactors filled with Pd catalysts within a Groundwater Circulation Well (GCW) system has been recently examined at bench scale and at field scale to treat plumes of groundwater contaminated with chlorinated ethenes. A short residence time of the groundwater passing through such catalytic fixed-bed reactors is expected to rapidly destroy the pollutants. This technique may be applicable for the treatment of groundwater contaminated with nitrate and nitrite as well since the Pd catalyst in presence of a suitable electron donor can reduce these pollutants into a harmless product (nitrogen gas).

Ongoing investigations in this research project are:

(a) Assess the effectiveness and limitations of Pd catalysts in a fixed bed reactor at bench scale (batch and column reactor systems) for field applications. This includes assessing the effect of substrates (nitrate and nitrite) concentration, Pd catalyst concentration, hydrogen and formic acid concentration as electron donors, and residence time on reaction kinetics.

(b) Further evaluate the impact of key geochemical parameters such as (i) pH, (ii) bicarbonate alkalinity, and (iii) biogenic sulfide, on the reaction rate constant.

(c) Develop and test an inexpensive and robust technique for the treatment of groundwater contaminated with this most common pollutant that is easily installed at contaminated sites, and that also supports long-term in situ remediation with limited maintenance.