The use of crossflow microfiltration in wastewater treatment is limited because of membrane fouling as a result of the colloidal fraction. A large part of this colloidal fraction can be converted into a settleable particulate fraction through a pretreatment combining electrocoagulation and aeroflotation. Permeation flow with a 0.1 mum microporous membrane increases from 0.02 m3/m2 h for untreated water to a value approaching 0.35 m3/m2 h for pretreated water.