Impacts of hydration and dehydration on microfiltration point-of-use filters: performance and cleaning impacts

Abstract

This research examines the performance of two commercially available point-of-use (POU) microfiltration membrane filters (MF) under hydrated (wet) versus a multi-day dry period (dehydrated). Filter performance is monitored in terms of water quality and flowrate, as well as flowrate recovery following different cleaning regimes. The cleaning methods tested were backwashing with filtrate at room temperature, filtrate heated to 45 °C, filtrate at 45 °C with gentle shaking, and a vinegar solution (5% acetic acid). The selected cleaning methods reflect easily accessible cleaning methods with a goal to assess their impacts on flowrate recovery under both wet and dry conditions. After initial testing, hydrated MF flowrate varied between 197 ± 22 mL/min and backwashing with filtrate at room temperature was sufficient to maintain the membrane flowrate, while any of the other methods initially improved the system flowrate. In experiments where the filters were subject to a 5-day dry condition MF flowrates dropped to 65 ± 35 mL/min and filtrate at room temperature did not recover the flowrate sufficiently, however heated filtrate (45 °C) with/without gentle shaking was effective at recovering the MF for use. Water quality remained similar throughout the study, and 0 CFU/mL of E. coli were found in filtrate samples. HIGHLIGHTS This research provides a side-by-side comparison of POU membrane filters when maintained under wet versus dry conditions.; Heated filtrate was found to positively improve membrane filter performance after fouling under all conditions.; Overnight soaking of a dried membrane did not adequately recover membrane filter performance.; Complete turbidity removal was observed under repeated wet and dry conditions.;

Keywords

• backwashing
• hollow-fiber
• membrane
• microfiltration
• point-of-use