Environmental management of the residual brine of cod desalting. Quantification of mass transfer phenomena and determination of some parameters on the residual brine important for its treatment by membrane technology

The changes of the society nutrition habits and the attempt for satisfying the consumer’s demands have forced the cod industry to develop a wide variety of cod desalting products. Residual brine generated in the cod desalting process is an effluent with dissolved and suspended solids which must be treated before its spill to municipal sewage system. The aim of this work was to quantify the volume of residual brine generated in an industrial cod desalting process and to determine its composition in order to establish its environmental management through membrane technology. The residual brine used came from desalting of salted codfish, with a 1:7 parts in mass cod:water ratio. The results showed that during the desalting process mainly NaCl and, to a lesser extent, proteins, were transferred to the desalting solution, forming the residual brine. Particle size measurement showed a wide range of suspended particle with multimodal distribution and size greater to 0.3 μm (diameter of a sphere equivalent in volume), whereas low zeta potential (ζ) was measured, indicating a low stability of suspended particles.