TREATMENT OF AN OIL GREASE WASTE-WATER USING ULTRAFILTRATION - PILOT-SCALE RESULTS/

Wastewater containing about 0.5% oil and grease (O/G) from a metal ind ustry was treated by tubular ultrafiltration using membranes having a molecular weight cutoff (MWCO) of 120,000 and a negative surface charg e (P membrane) and of 100,000 and no surface charge (M membrane), Perm eate flux decreased dramatically during the first several hours of ope ration and then leveled-off for the remainder of semibatch operation. The average P membrane flux was significantly higher than the M membra ne (38 versus 27 gal/ft(2).d) because of its higher MWCO and negative surface charge. Increasing the transmembrane pressure and crossflow ve locity increased the permeate flux for both membranes. O/G concentrati ons less than 50 mg/L and total suspended solids (TSS) levels less tha n 25 mg/L were common for both membranes. O/G removal efficiencies (re jections) averaged 98% for the M membrane and 97% for the P membrane. TSS rejections were approximately 97% for both membranes. Effluent O/G concentration and turbidity from the P membrane were slightly higher than the M membrane because of the P membrane's higher MWCO and the la rger flux. The average volume reduction and residual production were 9 7% and 32 gal/1000 gal, respectively, Acid cracking of the concentrate with sulfuric acid was marginally successful.