Peldszus et al | http://dx.doi.org/10.5942/jawwa.2012.104.0093 Journal - American Water Works Association Peer-Reviewed E430 2012 © American Water Works Association Because of the major impact of fouling on membrane opera- tion, fouling mitigation is of crucial importance. For low-pressure membranes used for drinking water production, foulants include particulate, colloidal, and organic raw water constituents. In recent years, the fouling potential of different natural organic matter fractions has been investigated with varying results (Her et al, 2007; Kimura et al, 2004; Lee et al, 2004). Within the past several years, biopolymers, which are a component of natural organic matter or of effluent organic matter composed of polysac- charides and proteins or proteinlike substances, have been dem- onstrated to play an important role in both hydraulically revers- ible and irreversible fouling of low-pressure membranes (Haberkamp et al, 2011; Peldszus et al, 2011; Hallé et al, 2009; Haberkamp, 2008). Thus processes capable of removing biopoly- mers can play an important role in reducing fouling of ultrafiltra- tion (UF) membranes. Because biopolymers are biodegradable, biological filtration should be capable of reducing membrane fouling. In the past several years biological filtration has attracted increased interest in the water industry, although essentially for other applications. The most common of these related to the removal of organic carbon include control of bacterial regrowth in distribution sys- tems, reducing chlorination by-product formation potential (Niquette et al, 1999), and taste and odor control (Elhadi et al, 2006; Westerhoff et al, 2005). A summary of the current state of biofiltration knowledge, including modeling and an approach for design, can be found in Huck and Soza´ nski (2008). Biofiltration for membrane pretreatment is a fairly new appli- cation (Persson et al, 2006; Hu et al, 2005). Although biofiltra- tion preceded by ozonation as a UF pretreatment is being used at full scale (Farr & Stampone, 2007), this process has not been investigated in detail. Hallé et al (2009) examined the use of biofiltration without prior coagulation or ozone addition as a novel membrane pretreatment to reduce membrane fouling. That study was conducted using relatively small-scale (50-mm-diame- ter) filtration columns and a bench-scale UF unit. Building on previous laboratory investigations using synthetic water (Mosqueda-Jimenez et al, 2008; Basu & Huck, 2004) the inves- tigation by Hallé et al (2009) used water from an impacted river having a broad range of temperatures and total organic carbon (TOC) of approximately 7 mg/L C and provided “proof of con- cept” that this process could deliver effective reduction in fouling for a UF membrane. A relatively new analytical tool that was available for the Hallé et al investigations was liquid chromatography with organic carbon detection (LC/OCD; Huber et al, 2011). This technique allows quantification of the major dissolved organic carbon (DOC) fractions present in a given water, and in the current context was instrumental in demonstrating the role of the bio- polymer fraction in membrane fouling (Figure 1). Such biopoly- mers may be present either from sources such as upstream waste- water discharges or produced in situ by biological activity in a river, lake, or reservoir. Figure 1 shows the major DOC compo- nents in Grand River (Ontario, Canada) water (after biofiltration) as well as the retention of biopolymers by the membrane (data from pilot study). An important finding of the Hallé et al study was that biopoly- mer removal increased with increased biofiltration empty bed Broader application of ultrafiltration (UF) membranes in drinking water treatment is limited by particulate and organic fouling. This pilot-scale study demonstrated the ability of rapid biofiltration (without prior coagulation or ozonation) to reduce fouling of a UF membrane treating impacted river water over a two-year period. Three biofilter empty bed contact times (EBCTs; 5, 10, and 15 min) were investigated, using parallel dual-media filters followed by a hollow-fiber membrane unit. Utilizing essentially conventional rapid filtration operating conditions, biofiltration pretreatment enabled stable membrane operation with respect to hydraulically reversible and irreversible fouling. Increased biofiltration EBCTs led to lower rates of irreversible fouling. The results were reproducible, and biofiltration was able to provide effective pretreatment during all seasons (T = 1–25°C). The biofilters also contributed to effective turbidity removal. Overall, biofiltration pretreatment for UF is a promising chemical-free alternative to coagulation pretreatment. A particular niche application would be in small or remote systems. Direct biofiltration pretreatment for fouling control of ultrafiltration membranes SIGRID PELDSZUS 1 , JAN BENECKE 2 , MARTIN JEKEL 2 , PETER.M. HUCK 1 1 Department of Civil and Environmental Engineering, University of Waterloo, Ontario 2 Department of Water Quality Control, Technische Universität Berlin, Germany KEYWORDS: biofiltration, ultrafiltration, fouling reduction, pilot scale, organic fouling