The purpose of this research was to evaluate different pretreatment alternatives for microbial removal efficacy using a seasonally brackish surface water. The following three pretreatment systems were evaluated: the Super Pulsator (SuperP) blanket clarifier followed by dual media gravity filtration; the Actiflo micro-sand ballasted clarifier followed by dual media gravity filtration; and, the Zenon immersed ultra-filter. From September through October 2002, microbial challenge studies were conducted on these pretreatment systems. The challenges used MS-2 phages, PRD-1 phages, and 3-micron beads to compare the removal efficacy of the pretreatment systems. Further, background fecal and total coliform removals were evaluated. Includes tables.