A process for separating organic components from a pulp mill waste stream comprising the steps of washing a cellulose pulp to obtain an aqueous extraction liquor containing organic components, and separating at least a portion of said organic components from the extraction liquor by passing the extraction liquor through at least one nanofiltration membrane. The process may be used in conjunction with a variety of pulp mill processes, including kraft cooking processes, hot caustic extraction processes, sulfite cooking processes, and bleaching processes.