Microfiltration of Lake Michigan Water for the production of drinking water was investigated using a 60 GPM Memcor micro filtration pilot plant for nine months at Manitowoc WI. The performance characteristics of a microfiltration pilot plant for varying surface water conditions were analyzed and modeled. Statistical regression was used to determine and develop quantitative relationships between time of operation and several operational variables for water quality and productivity. Direct filtration of a alum pretreated feed water was found to greatly increase time of operation between cleanings for temperatures below 48 degrees F. The investigation found the turbidity and particle counts of the microfiltered water was less than the same for the finished water produced by the conventional alum coagulation, sedimentation and filtration process. Cleaning frequencies of 21 or more were predicted. Based on the results of this investigation, a recommendation was made to use microfiltration as the treatment process of choice for the treatment of Lake Michigan Water.