Denitrification in USB reactor with granulated biomass

Abstract

Denitrification of low concentrations of NO 3–N (20 mg L −1), with methanol as an organic carbon source (COD:NO 3–N = 6) in laboratory upflow sludge bed reactor (USB), was tested as a possibility for wastewater post-treatment. By gradual increase of volumetric loading (Bv) and hydraulic loading ( γ), anoxic biomass spontaneously granulated out even from flocculate activated sludge and from anaerobic granulated sludge as well. Anaerobic granulated biomass derived from high-rate anaerobic IC reactor was a far better inoculum for anoxic granulation and for denitrification in the USB reactor. The maximum level of Bv and γ was remarkably higher with the use of anaerobic granulated inoculum, (19–22 kg COD m −3 d −1; 3.2–3.7 kg NO 3–N m −3 d −1; 2.8–3.2 m 3 m −2 h −1; SVI = 15 mL g −1) in comparison to inoculum from flocculate activated sludge (4.2–8.1 kg COD m −3 d −1; 0.7–1.4 kg NO 3–N m −3 d −1; 0.7–1.15 m 3 m −2 h −1; SVI = 40–95 mL g −1).