Nitrate removal by an ultra-compact biofilm reactor

This study consisted of two stages. The first stage was to cultivate denitr ifying biofilm with a simplified UCBR while the second stage was to investi gate the performance of a standard UCBR for nitrate removal. The volumetric nitrate-N conversion rate increased steadily from less than 0.5 kg/m(3).d to about 2.5 kg/m(3).d towards the end of Stage 1. Reactor instability and poor biofilm morphology had led to a relatively low nitrate-N conversion ra te during stage 1 of operation. In Stage 2, the conversion rate increased r apidly to 6.5 kg/m(3).d within 4 days and increased steadily to 10.5 kg/m(3 ).d, thereafter. The biofilm formation in Stage 2 was better than that atta ined in Stage 1. Biofilm density and biomass concentration in the reactor w ere in the range of 20.5 to 29.0 g/L and 1 to 3 g/L, respectively. The spec ific growth rate of the denitrifiers (mu) and the observed biomass growth y ield coefficient (Y-obs) in the reactor varied within the ranges of 1.5-4.2 d-1 and 0.20-0.65 g biomass/g nitrate-N, respectively. The specific nitrat e-N conversion rate (gamma) was within the range of 1.8-3.8 g nitrate-N/g b iomass.d.