Treatment of High Strength Wastewater in Thermophilic Anaerobic-Aerobic Moving Bed Biofilm Reactors

Abstract

Moving bed biofilm reactors were used for the thermophilic (55°C) anaerobic-aerobic treatment of a constructed high strength wastewater based on molasses. The anaerobic reactors were started with mesophilic inoculum, while the subsequent aerobic reactors were started without inoculation. The total amount of anaerobic biomass (suspended and attached) in the reactors stabilised at around 3 g VSS l⁻¹. Substrate utilisation rates up to 4.2 kg soluble chemical oxygen demand (SCOD) (kg VSS·d)⁻¹ were obtained at loading rates to the anaerobic biomass up to 16.4 kg SCOD (kg VSS·d)⁻¹. Volumetric removal rates up to 7.6 kg SCOD m⁻³d⁻¹ were achieved at loading rates up to 30 kg SCOD m⁻³d⁻¹ in the anaerobic reactors. The maximum loading capacity however, was not evaluated during the study. Average sludge yields of 0.25–0.28 kg VSS (kg SCOD_removed)⁻¹ were achieved in the anaerobic reactors. The total amounts of aerobic biomass varied between 1.1 and 2.5 g VSS l⁻¹. A maximum aerobic substrate utilisation rate of 4.6 kg SCOD (kg VSS·d)⁻¹ was achieved at an aerobic biomass loading rate of 18.4 kg SCOD (kg VSS·d)⁻¹. Volumetric removal rates up to 6.8 kg SCOD m⁻³d⁻¹ were achieved at loading rates up to 27 kg SCOD m⁻³d⁻¹ in the aerobic reactors. The maximum obtainable removal rates per biomass or volume were not reached during the study.

Keywords:

• Aerobic
• anaerobic
• high-strength wastewater
• moving bed biofilm reactor
• thermophilic treatment