Pilot and full scale applications of sulfur-based autotrophic denitrification process for nitrate removal from activated sludge process effluent

Sulfur-based autotrophic denitrification of nitrified activated sludge process effluent was studied in pilot and full scale column bioreactors. Three identical pilot scale column bio-reactors packed with varying sulfur/lime-stone ratios (1/1e3/1) were setup in a local wastewater treatment plant and the performances were compared under varying loading conditions for long-term operation. Complete denitrification was obtained in all pilot bioreactors even at nitrate loading of 10 mg NO3/C0 eN/(L.h). When the temperature decreased to 10/C14 C during the winter time at loading of 18 mg NO3/C0 eN/(L.h), denitrification efficiency decreased to 60e70% and the bioreactor with S/L ratio of 1/1 gave slightly better performance. A full scale sulfur-based autotrophic denitrification process with a S/L ratio of 1/1 was set up for the denitrification of an activated sludge process effluent with a flow rate of 40 m3/d. Almost complete denitrification was attained with a nitrate loading rate of 6.25 mg NO3/C0 eN/(L.h).