Review of the treatment of seafood processing wastewaters and recovery of proteins therein by membrane separation processes -: prospects of the ultrafiltration of wastewaters from the fish meal industry

The wastewaters generated in fish meal production (average flow rates of 1100 m(3)/h for a plant capacity of 100 ton fish/h) contain a high organic load, and therefore they should not be discharged directly into the sea without effective treatment in order to prevent a negative impact on the environment. On the other hand, these effluents contain a large amount of potentially valuable proteins. These proteins can be concentrated by means of ultrafiltration (UF) and recycled into the fish meal process, improving its quality and the economic benefits from the raw material, whereas the treated water can be discharged into the sea or reused in the plant. Due to the high concentration of suspended matter in these effluents, microfiltration (MF) pre-treatment is required. An extensive review of the application of pressure-driven membrane separation processes in the treatment of seafood processing effluents and recovery of proteins therein is presented. Two effluents from a fish meal plant located in Talcahuano, Chile, were characterised and microfiltrated with a Whatman filter No. 1. A mineral tubular membrane, Carbosep M2 (MWCO = 15 kDa, ID = 6 nun and L = 1.2 m) was used in the UF experiments. The operating conditions were optimised in total recirculation mode, and the subsequent concentration experiments were carried out at 4 bar, 4 m/s, ambient temperature and natural pH. The results show that UF reduces the organic load from the fish meal wastewaters and allows the recovery of valuable raw materials comprising proteins. Moreover, they point out that further investigation should be dedicated to the use of UF membranes of lower molecular weight cut-off-or even NF membranes-in order to achieve complete recovery of the proteins contained in these effluents. Although the membrane undergoes severe fouling, it can easily be cleaned through a caustic washing.