DAF pretreatment: its effect on MF performance

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Abstract
A pilot study suggests that DAF pretreatment helps reduce membrane fouling in hollow‐fiber MF.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/m2/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/m2/h), with run lengths of 21 and 10 days for fluxes of 110 and 135 gfd (190 and 230 L/m2/h). Experimental results from 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.