Hedieh Hashtroudi - Department of Chemical Engineering, Faculty of Engineering, University of Isfahan, Iran
Mehrdad Farhadian - Department of Chemical Engineering, Faculty of Engineering, University of Isfahan, Iran
Mehdi Borghei - Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran

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 (۳۵% of volume) with industrial packings made of polyethylene with an effective surface area of ۴۸۰ m۲/m۳ to provide the necessary surface for biofilm growth. The effect of various operating conditions, including hydraulic retention time (HRT = ۱۲-۲۰ hr), biomass concentration (۶۰۰۰– ۸۰۰۰ mg/L), and initial chemical oxygen demand (COD) (۳۰۰۰-۵۰۰۰ mg/L) level, were assessed on the overall COD removal efficiency using response surface methodology (RSM). The optimal conditions were an HRT = ۲۰ hr, biomass concentration = ۸۰۰۰ mg/L, an initial COD = ۳۰۰۰ mg/L, and an organic loading rate (OLR) of ۳.۶ kg COD/m۳.day under which the COD removal efficiency was ۹۸%. 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 ۵۸-۱۰۱.۶ and ۵۷.۵- ۹۷ 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.

Beet sugar, Kinetic coefficients, Hybrid bioreactor, Wastewater treatment