Hydrogenotrophic denitrification of drinking water using packed-bed reactors

A cluster of bench-scale packed-bed reactors was used to investigate nitrate removal from contaminated drinking water through hydrogenotrophic denitrification. A mixed culture originating from a wastewater treatment plant was used to inoculate four packed-bed reactors, with gravel as support media in different sizes (mean diameter 1.75, 2.41, 3.52 and 4.03 mm). We studied the effect of gravel size and operating mode (draw-fill or continuous) on filter performance. It was found that gravel size drastically affects the hydrogenotrophic denitrification rate, while draw-fill operation was more efficient for high nitrate nitrogen concentrations up to 200 mg/L. An increase of filter height increased drastically the retention time of the treated water and continuous operation became favourable for even higher nitrate nitrogen concentrations of 350 mg/L, where denitrification rates of about 6.5 g/Ld were achieved. The proposed procedure may prove to be an effective and economic method for nitrate removal from contaminated water resources.