A continuous process for treatment of dairy wastewater with immobiliz ed lactic acid bacteria has been demonstrated at pilot scale. A strai n of Lactobacillus plantarum was selected on the basis of a high conv ersion rate of lactose at low concentrations, and the ability to reta in activity for a long time immobilized in alginate beads. Lactose wa s converted to lactic acid, which lowered the pH and precipitated mil k proteins. The proteins were separated together with milk fat by flo tation with carboxy methyl cellulose (CMC) or chitosan and gave a sol id phase of approx. 10% dry matter (23% protein and 68% fat). The tot al chemical oxygen demand (CODt)removed varied from 65 to 78% for CMC and 49 to 82% for chitosan. The precipitated material was used as a feed supplement for pigs to provide up to 30% of the total energy int ake. No adverse effects on the pig's performance were observed. The e nergy feed value of the precipitate was estimated to be 2.0 feed unit s (FUs) per kg dry matter.