BACKGROUNDThe press juices resulting from a compacting operation on fish by-products were subjected to a depuration treatment in order to reduce the high COD (120g O-2 L-1). The process included an initial de-particulation step by means of two metallic filter cartridges of 465 mu m and 250 mu m, followed by concentration with a 200nm ultrafiltration ceramic membrane. The polishing efficiency of each unit was assessed in terms of COD and protein removal. RESULTSDead-end metallic filtration of the press waters reduced their suspended matter content by 28%, but achieved only 5.6% decrease in chemical oxygen demand (COD), which suggested further processing by membrane ultrafiltration. The de-particulated stream was then subjected to ultrafiltration for 8h in batch concentration mode, attaining a COD reduction of 87%. The observed flux of permeate was successfully fitted to a cake-forming model adapted to cross-flow filtration. The permeability of the fouled membrane was completely restored (99.87%) by a cleaning treatment comprising an alkali step with NaOH and a final disinfection with NaOCl. CONCLUSIONSThe treatment proposed has proved to be a feasible technology, able to render a final permeate with reduced organic load. (c) 2013 Society of Chemical Industry