Mass Transfer Coefficient (kL.a) Determination With Microelectrodes In Biofilms From An RBC At Different Operation Conditions

Abstract

The mass transfer coefficient of oxygen (kL.a) was determined for biofilms produced in a rotating biological contactor (RBC) by means of a microelectrode built at the laboratory. Three different rotational velocities (1.25, 2.75 and 5.25 rpm) were used for the determination. The microelectrode tip was made of platinum (99% purity); which was mechanically filed down from its initial diameter of 0.5 mm to 67 μm. The microelectrode was then mounted on a micromanipulator with a precision of 100 μm. The RBC was fed with municipal wastewater, reaching a removal efficiency of 65% as soluble COD and 96% removal of nitrogen as ammonia nitrogen (N-NH4). The hydraulic retention time (HRT) was 8 h. The average room temperature was 26.7 °C and the water temperature in the RBC was constant (22 °C) during the measurement. The kL.a determined at 1.25 rpm was 1.953 (day)-1, while that determined at 2.75 rpm was 3.117 (day)-1 and finally at 5.25 rpm was 9.799 (day)-1. The results confirmed the irregularity of the biofilm’s structure.