Cross-flow microfiltration using ceramic membranes applied to the cuttlefish effluents treatment: effect of operating parameters and the addition of pre or post-treatment

Cross-flow microfiltration alone or associated with ultrafiltration or coagulation was conducted to investigate the efficiency of this process in the reducing of chemical oxygen demand (COD) and proteins (Npr) in the waste waters produced from cuttlefish conditioning and freezing process. The study of the effect of operating parameters on the fouling of a ceramic microfiltration membrane (velocities and pressures) using real effluent showed that the maximum permeate flux was obtained at 5.6 m/s and 2 bar; it was about 120 l/h.m2. For the same initial COD, the last value increased by 28% and 40% respectively when the conductivity decreased from 50 to 0.6 mS/cm and the pH decreased from 7 to 4. However, the turbidity of the permeate and the retention rates of COD and nitrogen proteins were not affected by the variation of these parameters (0.8 NTU, 55% and 60% respectively). The flux enhancement was also studied by using a combination of microfiltration-ultrafiltration and aluminium salt and MgO coagulation-microfiltation. The same performances were obtained in the case of the use of combined SA-MgO-MF and MF-UF. The total resistance of fouling was less important in the latter cases. However, the irreversible resistance remained the main component in all cases. Maximum steady state flux was then 140 l/h.m2 obtained at the previously determined optimum conditions. The corresponding rejection of COD was better for SA-MgO-MF treatment (75% against 65%). However, the retention rate of nitrogen proteins was better for MF-UF treatment (78% against 57%).