Beet sugar wastewater treatment in a hybrid biological reactor: operational optimization and kinetic coefficients calculation

The lab-scale treatment of strong beet sugar wastewater was carried out with a combination of a moving bed biofilm reactor (MBBR) and upflow sludge blanket filtration (USBF). The hybrid bioreactor was filled (35% of volume) with industrial packings made of polyethylene with an effective surface area of 480 m2/m3 to provide the necessary surface for biofilm growth. The effect of various operating conditions, including hydraulic retention time (HRT = 12-20 hr), biomass concentration (6000– 8000 mg/L), and initial chemical oxygen demand (COD) (3000-5000 mg/L) level, were assessed on the overall COD removal efficiency using response surface methodology (RSM). The optimal conditions were an HRT = 20 hr, biomass concentration = 8000 mg/L, an initial COD = 3000 mg/L, and an organic loading rate (OLR) of 3.6 kg COD/m3.day under which the COD removal efficiency was 98%. The modified Stover–Kincannon model was applied to predict the biokinetic coefficients for COD removal; the saturation constant (KB) and the maximum total substrate utilization rate (Umax) were in the range 58-101.6 and 57.5- 97 as g/L.day, respectively.  The results revealed that raising HRT or biomass concentration promoted COD removal while increasing the initial COD deteriorated the removal performance.