Clean production in fish canning industries: recovery and reuse of selected wastes

Abstract

Fish canning industries generate a large number of different wastewaters that usually are treated together in a complex plant. However, some of these streams can be treated to recover additional subproducts as well as reducing the final volume of wastewaters. As a first example, oil and fat contained in cannery wastewaters are usually removed in conventional treatment plants with flotation devices. As a result of this operation, a stream that contains most of the oil, fat and floating matter is obtained, which can account for a large volume with high costs of disposal and/or treatment. A procedure based on the use of heat and centrifugation has been successfully used to generate three fractions: a solid phase, an aqueous phase and a 40–50% oily phase with similar characteristics to a fuel. A second example is focused on the effluent generated during the cooking of tuna, characterized by a high organic matter (COD 59 g/l) and total protein (20 g/l) content. This stream can be treated individually in an evaporation plant to obtain a concentrate with a high protein content, which could have interest as a complement in animal nutrition. Nutritional experiments were carried out on two groups of rats, showing that the addition of small quantities of concentrate to standard food (under 15% of weight), improve its digestibility and food intake.