Decontaminate river water via portable gravity-driven ultrafiltration (GDU) unit: Fouling and cleaning efficiencies studies

A gravity-driven ultrafiltration (GDU) membrane system was used for river water treatment under both depleting and constant hydrostatic pressure conditions. PVDF ultrafiltration membrane with mean pore size of 0.03 µm were assembled vertically in a 30 cm-height tubular column in two-pass to provide dead-end filtration mode. Their performance in terms of flux, rejection and fouling propensity were evaluated using both synthetic foulants and real river water. It was found that the GDU system is able to treat the river water with average flux of 21.77 L m⁻² h⁻¹ under constant hydrostatic conditions. It showed excellent (> 99%) removal towards the suspended solid and humic substance. Slight fouling by the humic substance and suspended solid were noticeable on the membrane surface, however, they could be cleaned by chemical washing, surface rinsing and backwashing. Backwashing, in particular, is found to be effective for removing the recalcitrant humic substance with flux and rejection recovery of more than 95%. Comparing the depleting and constant hydrostatic pressure system, the depleting hydrostatic pressure module could be used for at least 10 times before cleaning must be in place. It also showed promising pathogenic bacteria removal from the contaminated river water. This study showed that the GDU system especially the depleting hydrostatic pressure module is suitable to be used as small scale or individual/personal module for clean water production from river water.