GAS-LIQUID OXYGEN-TRANSFER CHARACTERISTICS IN AN AEROBIC SUBMERGED BIOFILTER FOR THE WASTE-WATER TREATMENT

Factors affecting the gas-liquid oxygen transfer characteristics in the biofilter with total floor coverage aeration were experimentally investigated. it was ascertained that an increase in the microbial concentration hinders the gas-liquid oxygen transfer rate in the biofilter due to the coalescence of air bubbles, while the oxygen transfer rate is considerably higher than that in the activated sludge aeration tank at the same gas flow rate. The packing materials in the biofilter control the bubble size, bubble rising velocity and the spiral liquid circulation rate caused by the air lift action. A formula for estimating K(L)a in the biofilter packed with ceramic balls of 6 -23 mm in diameter was obtained as a function of the packing material size and the microbial concentration in it. The maximum power economy of oxygen transfer in the biofilter, which is defined as the amount of oxygen dissolved into the liquid per unit power consumption, is as high as 3 kg-O2/kWh provided that the microbial concentration is in the rage of 2000 - 4000 g/m3.