| his research examined pre-coagulation and air sparging (surface shear stress) as fouling control strategies for ultrafiltration (UF) membranes during drinking water treatment of natural water matrices. In addition to fouling control, these treatment strategies were also examined with respect to any added benefit for the retention of organic micropollutants. A low coagulant dose (0.5 mg/L) was identified as optimum for biopolymer (foulant) removal, based on a point of diminishing returns analysis in three natural water matrices. This dose resulted in lower or equivalent fouling relative to a dose of 15 mg/L while providing similar retention of organic micropollutants (up to 40%). At pilot-scale, a 0.5 mg/L coagulant dose resulted in lower fouling (up to 77%) when compared to a 6 mg/L dose, while providing a similar reduction (up to 14%) of DBP formation.;Shear stress at the membrane surface, associated with varying air sparging conditions, was found to significantly reduce UF fouling for all waters investigated. Fouling reduction was most pronounced in waters with higher concentrations of organics and biopolymers, as shear stress was determined to decrease the fouling rate via back-transport of biopolymers from the membrane surface, preventing or slowing their deposition. The greatest fouling reduction was achieved with shear stress representative of large, pulse bubble (>100 mL) air sparging. With respect to fouling control, the potential for significant cost savings (up to... |
