Denitrifying Bacteria Populations and Nitrogen Removal in Soil Columns Intermittently Flooded with Secondary Sewage Effluent

Abstract

AbstractThe effects of infiltration rates and carbon treatments on denitrifying bacteria populations and N‐removal in soil columns intermittently flooded with secondary sewage effluent (SSE) were determined. At low infiltration rates of 10 to 15 cm/day, N‐removal by denitrification was >80% and enrichment of the SSE with organic carbon did not further enhance N loss, even though the denitrifying bacteria populations were increased. However, at higher infiltration rates (15 to 40 cm/day), the physiologically active denitrifying bacteria populations were effective in net N‐removal, and carbon enrichment of the SSE was essential for maintaining >80% N‐removal. Continuous carbon treatments were more effective than 2‐day pulse treatments for increasing the numbers of denitrifying bacteria and N‐removal. With continuous carbon treatments of 200 mg/liter, >80% N‐removal was obtained at infiltration rates of 40 cm/day. These results indicated that the activity of denitrifying bacteria and the N‐removal capacity of high‐rate land treatment systems could be enhanced by the timely additions of organic carbon to the SSE applied to the soil infiltration basins.