A systematic comparison of two empirical gas-liquid mass transfer determination methodologies to characterize methane biodegradation in stirred tank bioreactors.

This study aimed at systematically comparing the potential of two empirical methods for the estimation of the volumetric CH mass transfer coefficient (ka), namely gassing-out and oxygen transfer rate (OTR), to describe CH biodegradation in a fermenter operated with a methanotrophic consortium at 400, 600 and 800 rpm. The ka estimated from the OTR methodology accurately predicted the CH elimination capacity (EC) under CH mass transfer limiting conditions regardless of the stirring rate (∼9% of average error between empirical and estimated ECs). Thus, empirical CH-ECs of 37.8 ± 5.8, 42.5 ± 5.4 and 62.3 ± 5.2 g CH m hvs predicted CH-ECs of 35.6 ± 2.2, 50.1 ± 2.3 and 59.6 ± 3.4 g CH m h were recorded at 400, 600 and 800 rpm, respectively. The rapid Co-catalyzed reaction of O with SO in the vicinity of the gas-liquid interphase during OTR determinations, mimicking microbial CH uptake in the biotic experiments, was central to accurately describe the ka.