Fouling indices for low pressure hollow fiber membrane performance assessment

This study evaluated the use of fouling indices to describe low pressure membrane fouling. One critical aspect of this study was the use of a bench-scale hollow fiber membrane system that imitated full-scale operation (constant flux with automatic hydraulic backwash and chemical cleaning). Fouling indices were based on a resistance-in-series model. Two different hollow fiber membrane types (membrane A and B) were tested with water from two water utilities (A and B) and three other natural sources (oligotrophic, algal bloom impacted, and wastewater impaired). The bench-scale testing included use of the same membrane as utilized at Utility B. Most fouling was reversible by hydraulic backwash and chemical cleaning. Specific flux and fouling indices for the bench-scale system were higher than those determined from full-scale data but fouling index ratios were comparable, suggesting a similar fouling nature. At similar organic loading, fouling was specific to water source and membrane type, i.e., no generalization on the impact of water source was possible. Full-scale data were compared with bench-scale data to validate the use of fouling indices. Fouling indices based on a resistance-in-series are useful tools to describe membrane performance data for both raw and pretreated water, for different water sources, and different membrane types.