Biofiltration has long been used to treat drinking water in Europe and is becoming more widespread in North America. Pre-biofilters, or biofilters that operate as the first unit in a surface water treatment process train, are a cost-effective pretreatment for conventional surface water treatment and provide consistent downstream water quality. This paper describes a study that investigated the potential to remove total organic carbon (TOC)/dissolved organic carbon (DOC), and trihalomethane formation potential (THMFP) from surface water using prebiofilters. Furthermore, the impact of different molecular weight fractions of TOC/DOC and THMFPs in the surface water and the filtrates from the pre-biofilters were also investigated, respectively, in order to determine how well the prebiofilters can remove different fractions of TOC/DOC and THMFPs.