Method and apparatus for processing oily wastewater

A method of treating oily wastewater is described comprising the steps of passing oily wastewater through a coalescer to coalesce dispersed oil droplets; separating a free oil fraction as a liquid stream having a lower specific gravity from a contaminated water stream having a higher specific gravity; filtering particulate material from said contaminated water stream; passing the filtered water stream under pressure across an ultrafiltration membrane to separate a retentate fraction enriched in residual emulsified oil from an aqueous permeate fraction; recycling said substantially only retentate fraction to said coalescer; filtering said aqueous permeate through an activated carbon filter to remove low molecular weight organic materials; subjecting the filtrate from said activated carbon filter to cation exchange to remove heavy metal ions; and periodically flushing said ultra filter with filtrate from said particulate filter to maintain the permeability of said ultrafiltration membrane