PILOT-PLANT STUDIES ON THE ANAEROBIC TREATMENT OF DIFFERENT WASTEWATERS FROM A FISH-CANNING FACTORY

Most of the fish-canning factories are characterized by the variety of products to be processed and therefore by the production of effluents with different characteristics. When sea products are manufactured, generated wastewaters are very saline (10-20 g Cl-/l) and have a high content of organic matter (10-50 g COD/l). Based on previous studies of the characteristics of different streams generated at a representative factory, which cans tuna, mussel, octopus, sardine and also produces fish meal, and lab-scale studies showed the viability of the anaerobic treatment, a pilot plant was built in the factory. It consists of a predigester of 7 m3, a suspended sludge digester of 15 m3 and a clarifier of 3 m3. The main results can be summarized in these points: a) It is possible to obtain efficient anaerobic treatment of wastewaters with a concentration of chloride of 15 g/l. b) These wastewaters do not need the addition of nutrients, c) It is possible to treat individually or jointly all the streams generated in the factory. d) The particular results obtained with tuna- and mussel-canning effluents show that it is possible to reach 75-80% of COD removal when organic loading rates of 4 kg COD/m3.d were applied.