Pilot-scale ultrafiltration of an emulsified oil wastewater

Wastewater from a household appliance factory containing emulsified oil was treated using a separation method based on an ultrafiltration membrane. In itial wastewater characteristics were a chemical oxygen demand (COD) of 150 0 mg of O-2/L and a total hydrocarbon concentration (HC) of 170 mg/L. The c ross-flow pilot-scale study was performed with two commercial spiral-wound membrane modules having a molecular weight cutoff of 35 000 (M2 membrane) a nd of 2000 (M1 membrane). The M1 membrane showed COD and HC rejection perfo rmance higher than the M2 membrane. The M1 permeate flux and solute rejecti on were investigated in relation to the membrane pressure drop (Delta P= 10 0-400 kPa), temperature (20-35 degrees C), and feed cross-flow rate (2-5 m( 3)/h). The permeate flux was in good agreement with the expression of Darcy 's law, where the end-of-permeate flux is directly proportional to both app lied pressure and temperature. Results indicate that the fouling layer resi stance of the membrane was the dominant resistance and that it was mainly c aused by the emulsified oil adsorption on the surface and/or in the pore wa ll of the membrane. For design purposes, correlations to estimate both perm eate flux and COD-HC concentration in the retentate or permeate at any oper ational conditions (temperature, pressure, solution viscosity, concentratio n factor) have been obtained. Experimental pilot-scale tests had shown that an M1 ultrafiltration membrane is effective for removing emulsified oil an d achieving up to 90.1% and 99.7% removal of COD and HC, respectively, with a permeate flux of 20 L h(-1) m(-2) at Delta P = 400 kPa and 35 degrees C. It is pointed out that by optimizing the process design utilizing this mem brane module, it is possible to successfully apply the ultrafiltration memb rane technology to the treatment of industrial emulsified oil waste effluen ts.