REMOVAL OF AGRICULTURAL NITRATE FROM TILE-DRAINAGE EFFLUENT WATER USING IN-LINE BIOREACTORS

Two 200-L fixed-bed bioreactors, containing porous-medium material of coarse sand and organic carbon (tree bark, wood chips and leaf compost), were used to treat NO3 contamination from agricultural runoff. Flow from a farm-field drainage tile containing NO3-N concentrations of 3-6 mg L-1 was successfully treated in the reactors (NO3-N < 0.02 mg L-1) at a rate of 10-60 L day-1 over a 1-yr period. Treatment occurs by anaerobic denitrification promoted by the added solid-phase organic carbon. Because the reactor design is simple, economical to construct and maintenance free, it may provide a practical solution to the problem of treating redox-sensitive contaminants, such as NO3, in agricultural runoff.