Clean technology in fish processing industries Marlene Roeckel*, M. Cristina Martit and Estrella Aspe Depto de Ingenier[a Qu[mica, Fac. de Ingenieria, Casilla 53-C, Universidad de Concepci6n, Concepci6n, Chile tDepto de Farmacologia, Fac. de Ciencias Bioldgicas, Casilla 152-C, Universidad de Concepcidn, Concepci6n, Chile Received 15 September 1993 The effects of fish-meal manufacturing effluents on the seawater has reached troublesome levels in Chile, particularly in the VIIIth Region where most of the fish-meal industries are located. The scope of this work was to study the process, classi~ the pollutant streams, and pinpoint those steps that could be improved in order to reduce their contaminant effect, while salvaging reusable organic matter. As a result, we propose the introduction of a new step in the fish reduction process that involves recirculation of the pumping water used to unload the fish, screening of coarse organic matter, flocculation of soluble proteins in the recirculate and its separation by centrifugation, and the incorporation of both coarse and flocculated material to the reduction process. This reduces by 91.6% the estimated chemical oxygen demand (COD) value of a ton of processed fish and increases by 7% the industries' productivity. Reduction of the remnant organic load can be achieved by in-series anaerobic and aerobic degradation. The effect of the latter treatment reduces by an additional 5.6% the COD value. Marginal profits are higher than the treatment cost for high technology plants, as shown by a return on investment of 52.89% after a 5 year period. Keywords: fish-meal; wastewater treatment; clean technology Introduction Chile has become the most important producer of fish-meal in the world. In 1992 its total production I reached 1.23 × 106 ton of which approximately 60% was locally produced (Vlllth Region). While fish-meal production has steadily increased, it has severely damaged the environment owing to the dumping of wastewaters in the sea. Roughly 65 000 ton of COD per year have been poured into the nearby bays2, which are surrounded by 17 fish-meal factories (3.23 x I06 ton of fish processed during 1992). The Chilean Legislature is presently studying an Environmental Protection Act which will probably be enforced in the near future, so industries will have to comply to the set standards to avoid sizeable fines. This work is the result of a joint project involving an academic group, the regional Association of Fish Meal Producers, and government authorities, to solve the above-mentioned problems. The adequate handling of wastewaters should take into account the characteristics and final destination of all the streams involved in the process, so as to choose the best technology available for treatment at the lowest cost. Therefore, the goal of this work was *Correspondence to M. Roeckel 0959-6526/94/01/0031-05 ~) 1994 Butterworth-Heinemann Ltd to apply the clean technology concept to the local fish-meal processing industries, so as to minimize the liquid residues that they generate and, at the same time, increase their productivity. To achieve this, different wastewater treatments for liquid effluents were assayed, at laboratory and pilot scale, to deter- mine their depuration efficiency and their implemen- tation cost. Liquid effluents from the fish-meal industry Wastewaters from the local fish-meal industries are rich in organic matter, particularly soluble proteins, which can be recovered for the production process. The remnant organic matter may be treated by a sequential anaerobic-aerobic degradation. An important feature of these effluents is that they are not continuously generated, but when they are being generated they tend to be highly concentrated owing to a significant seasonal variation in fish catch (industries usually process more fish during the late autumn and early winter months3), and the unloading of huge amounts of fish from the ships in a very short time (up to 36000 ton per day). Furthermore, 17 fish- meal industries are located quite near the shoreline of three adjacent bays (Figure 1), thus the site of effluent dumping is a fairly confined area. J. Cleaner Prod. 1994 Volume 2 Number 1 31