The purpose of the membrane pilot study for the City of Grand Blanc was to establish the following: evaluate contaminant removal efficiencies (percent), and determine feed water blending ratios to achieve the target effluent water quality goals; evaluate performance of product flux over time, and monitor water quality; measure change in trans-membrane pressure (TMP) over time, TMP being the driving force between the concentrate pressure and permeate pressure; measure reject stream characteristics and evaluate options for discharging the reject water (including discharging the reject water to the Genessee County sewer system); evaluate the relative effectiveness of two different membrane materials for arsenic control; evaluate the applicability of the existing iron removal plants as a pretreatment step to the proposed membrane plants; and, develop a basis of design for the proposed membrane plants. A skid-mounted membrane pilot plant unit, with a 10 gpm capacity, was utilized for this study. The membrane skid was supplied by Osmonics, Inc. The pilot unit was operated at both Wells 5/8 and Well 7 locations. A by-pass from the iron removal plant finished water line was used to feed the membrane pilot unit. Sodium bisulfite was added to the membrane feed water to quench the chlorine residual. An anti-scalant chemical was added to the feed water to prevent the salts from precipitating on the membranes. A conductivity meter was mounted on the permeate water line. The pilot plant was operated from December 26, 2001 through February 6, 2002. The pilot plant was operated on a continuous 24-hour per day basis. No major operational problems were encountered during the pilot study, except for a malfunction of the pressure sensor on the permeate side. The following operational and water quality parameters were monitored on a daily basis: pre- and post- cartridge filter pressures; membrane influent pressure; permeate and reject flows; percent recovery; and, permeate conductivity, permeate pH, and free chlorine residual. Water samples were collected and analyzed for the following water quality parameters twice a week or daily at the two locations: hardness; chloride; fluoride; total arsenic; and, total dissolved solids. Includes 2 references, tables, figures.