Biological wastewater treatment in the inverse fluidised bed reactor

摘要

The biological wastewater treatment was investigated in the inverse fluidised bed reactor (IFBR) in which polypropylene particles of density 910kg/m3 were fluidised by an upward flow of gas. Measurements of chemical oxygen demand (COD) versus residence time t were performed for various ratios of settled bed volume to reactor volume (V_b/V_r) and air velocities u_g.The largest COD removal was attained when the reactor was operated at the ratio (V_b/V_R)_m =0.55 and an air velocity u_(gm)= 0.024 m/s. Under these conditions, the value of COD was practically at steady state for times greater than 30 h. Thus, these values of (V_b/V_R)_m, u_(gm) and t can be considered as the optimal operating parameters for a reactor when used in treatment of industrial wastewaters. A decrease in COD from 36,650 to 1950 mg/l, i.e. a 95% COD reduction, was achieved when the reactor was optimally controlled at (V_b/V_R)_m = 0.55,u_(gm) = 0.024m/s and t=30h. The pH was controlled in the range 6.5-7.0 and the temperature was maintained at 28-30 ℃.The biomass loading was successfully controlled in an IFBR with support particles whose matrix particle density was smaller than that of liquid. The steady-state biomass loading depended on the ratio (V_b/V_R) and an air velocity u_g. In the culture conducted after switching from the batch to the continuous operation, the steady-state biomass loading was attained after approximately 2-week operation. In the cultures conducted after change in (V_b/V_R) at a set u_g, the steady-state mass of cells grown on the particles was achieved after about 6-day operation. For a set ratio (V_b/V_R), the biomass loading depended on u_g. With change inu_g at a set (V_b/V_R), the new steady-state biomass loading occurred after the culturing for about 2 days.