Two-stage biological fluidized bed treatment of coke plant wastewater for nitrogen control

Abstract

raw wastewater provides the energy source and serves as the electron donor for the denitrification reaction. Full-scale in dustrial experience16 and cost comparisons based on municipal systems17 have indicated the potential of the pre-denitrification process for nitrogen control. The process flowsheet of the coupled, two-stage fluidized bed pilot plant is shown in Figure 1. The pilot plant consisted of an anoxic denitrification fluidized bed reactor, 150 mm in di ameter, and an oxygenic nitrification fluidized bed reactor, 290 mm in diameter. The initial empty bed reactor volumes were 58.5 L and 210 L for the anoxic and oxygenic beds, respectively. However, the bed heights and reactor volumes were adjustable by relocating the position of the sand-biomass separation systems. Pure oxygen was supplied to the nitrification reactor through a proprietary oxygen transfer device (Dorr-Oliver Inc.). High internal recycle rates were necessary for both reactors to maintain the required fluidization fluxes, to ensure an adequate oxygen supply to the nitrification process and to return nitrate and nitrite to the denitrification reactor. The support media in both reactors was quartzite sand with an effective size of 0.48 mm and a uniformity coefficient of 1.23.