DAF pretreatment: its effect on MF performance

A pilot study investigated the use of dissolved air flotation (DAF) as a pretreatment to hollow-fiber microfiltration (MF). Results showed that DAF-pretreated feedwater achieved longer MF runs than raw feedwater. MF performances with DAF-pretreated water were compared for fluxes of 70, 90, 110, and 135 gfd (120, 155, 190, and 230 L/m 2 /h). Performance results indicated that MF run lengths of more than 30 days could be achieved at flux conditions of 70 and 90 gfd (120 and 155 L/m 2 /h), with run lengths of 21 and 10 days for fluxes of 110 and gfd (190 and 230 L/m 2 /h). Experimental results fromi this pilot study were also interpreted using a mathematical model to determine MF backwash efficiency at the different flux conditions. Both the experimental and modeling results suggest that membrane fouling by the DAF-pretreated water was characterized by reduced pore blockage and lower cake compressibility as compared with treatment of raw feedwater.