OFF-GAS RECYCLE FOR VOC EMISSION CONTROL - CONCEPTUAL-MODEL

Capture and recycle Of Off-gas from a complete-mix activated-sludge re actor was evaluated as an alternative VOC-control strategy to reduce t he volume and cost of off-gas treatment. A mathematical model was deve loped to predict the fraction of individual influent VOC compounds tha t are biodegraded, stripped, and discharged in the liquid and gaseous effluents of an activated-sludge reactor with off-gas recycle. The mod el utilizes fundamental physical and biokinetic growth and substrate-r emoval constants for each VOC. The results indicated that for a biodeg radable VOC off-gas recycle increased biodegradation and reduced strip ping of the compound. The fate of a VOC depended on the relative magni tude of H(C), mu(MAX), and K(S), rather than their absolute values. Th e fate of VOCs having certain combinations of these parameters can be controlled by process and operational parameters of the activated slud ge and off-gas recycle system. These benefits are obtained without add itional energy utilization.