Application of microfiltration and ceramic membranes for treatment of salted aqueous effluents from fish processing

The results of microfiltration (MF) studies using ceramic 150 kDa membrane and model solutions containing bovine serum albumin (BSA) with and without NaCl as well as salted wastewater from fish industry are reported. The aim of the research was experimental analysis of operating parameters enabling regeneration of waste brine for recycling purposes. In the first step of the research effect of pH, NaCl concentrations, and pressure difference across the membrane on BSA rejection and permeate flux was experimentally investigated. The transmembrane pressure was changed in the range of 0.05 Á 0.2 MPa. MF tests were performed at temperature 208C and cross-flow velocity of 4 m/s using feed consisted of BSA (1.0 g/dm3) and NaCl (10 wt.%). In the second step of the research industrial brine from fish processing was characterized and pretreated by bag filters 100 and 1 mm. The MF tests with brine were performed in concentration mode, without permeate recycling to feed tank. The high protein rejection (81%) and significant rejection of BOD and COD, 72 and 60%, respectively, was observed.

The data and analysis presented in this paper are focused on the behavior of MF, ceramic 150 kDa membrane in separation of large molecule substances from salted aqueous solutions. Selectivity, permeability, and fouling of ceramic membrane in cross-flow filtration of model BSA solutions are depended on pH, TMP, and presence of sodium chloride in the feed solution. The lowest permeate flux was observed at pH 4.8 close to isoelectric point of BSA (pI 04.9) and the highest at pH 09.0. The addition of 10% of NaCl causes decrease of BSA rejection due to hindering of protein aggregation and reducing of protein adsorption on membrane surface. The results of fouling analysis indicate that irreversible fouling resistance RFir has major influence on permeate flux in the investigated model systems. Membrane RM and reversible fouling, RFre resistances had lower influence on flux decline. The extent of fouling decreases with pH increases and rises with salt concentration increases. The lowest fouling was obtained for pH 09.0. Addition of NaCl (10 wt.%) caused / / / increase of fouling extent from about 45% to 75% of total resistance for pH 09.0. Such selectivity Á permeability analysis in the model systems provide a framework that can be used to analyze the performance of investigated membrane in treatment of real salted aqueous effluent from fish processing with the aim to reuse of purified streams. The investigated membrane shows considerable difference in its selectivity to substances contained in salted wastewater from fish industry. The rejection coefficients for NaCl (6.5%) and total solids (14%) are definitely lower than for protein (81%). The obtained results confirm the advantages of examined ceramic membranes for removal of large molecule substances from solution consisted of solvent (water) and small solutes (NaCl). The values of permeate flux during MF of pretreated salted waters using bag filters was comparable to fluxes obtained for BSA/NaCl model system at low TMP. On contrary, it was found that at higher TMP the flux Á pressure dependence showed considerable difference between model and real systems. It requires of searching more adequate model system for further research. For the selection and development of condition for appropriate performance of investigated membrane in treatment of salted aqueous effluents from fish processing next experiments are necessary in both, model as well as real systems. /