[Wastewater treatment using a microbubble aerated biofilm reactor]

Microbubble aeration is supposed to be able to provide potential advantage for aerobic biological wastewater treatment due to enhancement of oxygen mass transfer. Biofilm reactor is considered to be feasible for application of microbubble aeration. Shirasu porous glass (SPG) membrane was used for microbubble aeration in a biofilm reactor to treat synthetic municipal wastewater. The air permeability of SPG membranes, dissolved oxygen (DO) concentration, pollutant removal and oxygen utilization were investigated during the continuous operation of the bioreactor. The long-term stable continuous operation of the experimental system demonstrated the successful application of microbubble aeration in aerobic wastewater treatment processes. The air permeability of SPG membranes was influenced by its surface wettability and pore size. The air permeability of hydrophobic membrane was better than that of hydrophilic membrane. The air permeability could also be improved by increasing the pore size. DO concentration was affected by organic loading mainly at a certain air flux. The optimal SPG membrane area-based COD removal capacity of the experimental system was determined as 6.88 kg x (m2 x d)(-1). NH4(+)-N removal was mainly affected by DO concentration and its diffusion inside the biofilm. The simultaneous nitrification and denitrification was observed at a high organic loading rate. The oxygen utilization was much more efficient in microbubble aeration, compared to traditional bubble aeration, and it might be close to 100% at optimal running conditions.