Removal of easily biodegradable organic compounds by drinking water biofilms: Analysis of kinetics and mass transfer

This paper evaluates the rate of utilization of easily biodegradable organi c compounds by drinking water biofilms. Tap water, which had been filtered through biologically active granular activated carbon, was used as an innoc ulum for biofilm growth in annular reactors (ARs). Synthetic cocktails of e asily biodegradable material in the concentration range of 50-2000 mg C/m(3 ) were used as substrate for biofilm growth. Influent and effluent aggregat e concentrations of biodegradable organic matter (BOM) were calculated by a dding the measurable BOM components on a mass carbon basis. The aggregate B OM values were used for calculating the observed Damkohler number and Theil e modulus (based on a reaction rate per unit surface area), which were used to determine whether external or internal mass transfer limited BOM remova l. For all of the experimental trials, it was shown that neither external n or internal mass transfer limited BOM removal. Because the biofilms in this research ore thin and the Tact that mass transfer is not limiting, it was assumed that the bulk BOM concentration was approximately equal to the aver age BOM concentration in the biofilm. A linear model was obtained for the a ggregate BOM flux and the product of the effluent BOM concentration and the biofilm density. The slope or the areal biodegradation rate (k(a)) for the aggregate BOM was 0.033 m/h, as determined through a linear regression. (C ) 2001 Elsevier Science Ltd. All rights reserved.