ABSTRACT
A biological reactor for denitrification above ground combined with re-infiltration for removal of organic matter was tested for treatment of nitrate contaminated groundwater. In a column test pulp mixed with sand was used for the biological reactor. A sand column, where unsaturated conditions prevailed, simulated the re-infiltration. The test study was run for 255 days with a hydraulic load of 0.22 m/h. After a start up phase of 30 days a nitrate reduction of 70–100% was obtained with exception for a break-through period probably caused by a short stop in the nitrate input. After about 200 days the reduction declined. The TOC concentrations after the biological reactor was about 4.5 mg/dm3 and no significant reduction was obtained in the sand column. However an efficient reduction in substances causing taste and odour in the water was observed.
