Fish meal industry, which is ranked among the water-intensive industries, is a very important industry in Chile. The wastewaters generated during the fish meal production, the flow rates of which are ca. 2040 m3/h for a plant capacity of 100 ton fish per hour, contain a high organic load, *Corresponding author. and present high turbidity, strong greenish yellow colour and stinky odour. Unlike other types of municipal and industrial effluents, these waste- waters do not contain known toxic or carcinogenic materials. In order to comply with the maximum limits set by the previous Chilean regulations on waste- waters discharges some fish meal factories have acquired dissolved air flotation (DAF) plants to