抄録
It is necessary to reduce costs in operation of membrane bioreactors (MBRs) for widespread use of the technology. Aeration used for prevention of attachment of biomass on the membrane surface accounts for the largest portion of the total energy consumption in MBRs and therefore should be focused on. Placing biomass carriers in submerged MBRs has been examined and been reported to be effective in mitigation of membrane fouling. In our bench–scale experiments in which a submerged flat–sheet MBR was operated with cylindrical carriers made from PEG, it was estimated that aeration rate in MBRs could be reduced by 50%. This estimation was verified in a pilot–scale MBR treating municipal wastewater. In that pilot–scale experiment, however, it was found that the carriers introduced caused damages on a part of membrane structures. Observations with a high–speed digital camera revealed that carriers moved much more rapidly in the pilot–scale MBR than in the bench–scale MBR. Also, the carriers moved randomly in the pilot–scale MBR whereas they steadily moved up almost perpendicularly in the bench–scale MBR. These differences in the manner of movement of the carriers in the MBRs seemed to explain the difference in the damage of the membrane in the two MBRs. Modification of aeration in the pilot–scale MBR is likely to avoid the damage on the membrane and is now being examined in our laboratory.
