Feasibility investigation of refinery wastewater treatment by combination of PACs and coagulant with ultrafiltration

This laboratory scale study investigated the effectiveness of ultrafiltration (UF) technology for treatment of refinery wastewater using powdered activated carbons (PACs) and coagulant. Flux decline, removal rates of total organic compounds (TOCs) and the possibilities of membrane cleaning during intermittent backwashing were studied. Addition of two kinds of typical PACs, PACs-1 and PACs-2, showed that the UF unit performance by adding PACs-2 was better than that of PACs-1. Suitable amounts were 20 mg.L−1. When different kinds of coagulant, HYM, HY-3, HYC-601 and HCA, were added into the wastewater samples, respectively, it indicated that the HCA system was well resistant to membrane fouling. Investigation also showed that the UF unit performance could be significantly improved by simultaneously adding 15 mg.L−1 of PACs-2 and 0.8 ml.L−1 of HCA into the system. The removal rates of TOCs in the wastewater were over 99%.

This laboratory scale study investigated the effectiveness of UF technology for treatment of refinery wastewater in the presence of PACs and coagulant, in terms of flux decline, removal rates of TOCs and the possibilities of membrane cleaning during intermittent backwashing. The experiments of adding two kinds of typical PACs, PACs-1 and PACs-2, into the wastewater system indicated that the decreasing trend of flux obviously reduced but usually leading the small drop in the permeate flux. However, when the additional amounts of PACs (PACs-1 or PACs-2) in the unit reached 20 mg.L−1 during the experiment, it showed that not only the initial flux was increased but also the decreasing trend of flux was definitely reduced. Further study proved that the UF unit performance by adding PACs-2 was better than Table 5 Turbidity, transmittance and organics data about 3,000 ppm mixed organics in water for 60 h run time Samples Turbidity, NTU Transmittance, % Organics conc., ppm Initial None YL-200-II, 10 mg.L−1 + HCA, 0.8 ml.L−1 Backwash time, s Final Initial Final Initial Final 3.25 26.00 0.28 0.23 98.0 94.1 99.7 <20 Removal rates, % 97.0 >99.0 that of PACs-1. It also indicated that the membrane flux could be recovered by a backwashing process for 30 s when the UF unit had been operating for 5 h. When different kinds of coagulants, HYM, HY-3, HYC-601 and HCA, were added into the wastewater samples respectively, it indicated that the system of adding HCA was well resistant to membrane fouling. Finally, it showed that the UF unit performance could be obviously improved by simultaneously adding PACs-2 and HCA into the system. The suitable amounts for PACs-2 and HCA were 15 mg.L−1 and 0.8 ml.L−1 respectively, in which the removal rates of TOCs in the wastewater were over 99%.