Abstract
In a wastewater treatment process consisting of a UASB reactor and aerobic post treatment, excess biogas is produced during the warm season. Methane-dependent nitrate removal using a biogas scrubber would be an efficient way to utilize the excess biogas. The performance of the plastic media-filled packed-bed reactor was examined for biogas scrubbing and methane-dependent nitrate removal. A bench-scale packed-bed reactor was installed in a swine wastewater treatment plant consisting of a UASB reactor and a trickling filter. The biogas from the UASB reactor was supplied from the bottom (3.4-9.4 m d-1), and the trickling filter effluent was spread from the top (9.4-26.1m3 m-2 d-1) . The concentration of H2S dropped from 1200-2500 ppm to less than 2 ppm. The plastic media covered with biofilm were then collected from the reactor and filled into a laboratory scale packed-bed reactor. Inorganic medium containing 40 mg-N l-1 nitrate was spread from the top of this reactor (1.4 m3 m-2 d-1), and gas was supplied from the bottom (25-36.5 m d-1) . The nitrate concentration dropped significantly when CH4 (93%v/v) and O2 (7%v/v) were supplied simultaneously. In contrast, nitrate removal scarcely occurred when only CH4 or He was supplied. These results suggest that simultaneous biogas scrubbing and methane-dependent nitrate removal are possible with the packed-bed reactor.
