Monitoring of biofouling on ultrafiltration hollow fiber membranes by rapid enzyme activity assays

The biofouling of an ultrafiltration (UF) membrane unit applied for drinking water treatment was investigated under three different operating conditions, i.e. flux 50, 60 and 70 L m⁻² h⁻¹. The biofouling was monitored by analyzing the enzyme (esterase and peptidase) activity on the sacrificed membrane fibers of a test unit installed in the same reactor as the membrane pilot module. At a given flux, a decrease of membrane permeability generally corresponded to an increase of enzyme activity. Enzyme activity could therefore be used to predict the permeability decline and potentially be used for e.g. at-line monitoring of membrane biofouling.