Bioscrubbing of Process Air Emissions: When Does it Work?

This study evaluated the potential of treating air emissions, collected from an industrial wastewater sump, in a proposed membrane bioreactor installation using TOXCHEM+ fate software. The bioscrubbing opportunity was assessed with the sump off-gas alone, and with subsequent modification to include possible additional treatment of exhaust from a cooling tower that might be inserted upstream of the planned MBR. The modeling results revealed that by directing the sump exhaust to the aeration basin for bioscrubbing, overall system emission rates would be reduced by approximately 88%. Because of the very high ventilation rates required by the cooling tower, however, a bioscrubber application involving the sump of-gas together with the cooling tower exhaust would have a detrimental effect on total plant emissions, due to the increased transfer of the contaminants in the aeration basin to the atmosphere. It thus appeared that it is better overall to allow the exhaust from the cooling towers to escape to the atmosphere (or to be treated elsewhere), rather than using the aeration basin as a bioscrubber for the high volume cooling tower exhaust.