Gravity-Driven Membrane Filtration with Passive Hydraulic Fouling Control for Drinking Water Treatment: Demonstration of Long-Term Performance at Full Scale

The present study evaluated the performance of a full-scale gravity-driven membrane filtration system with passive hydraulic fouling control (PGDMF) for drinking water treatment in a small community over a 3-year period. The PGDMF system consistently met the design flow and regulated water quality/performance parameters (i.e., total coliform, <i>Escherichia coli</i>, turbidity, and membrane integrity). The instantaneous temperature-corrected permeability (TCP) varied seasonally, being greater during the winter months. The overall TCP decreased slowly to ∼60% of the initial value by the end of 3 years, a TCP that is much greater than would have been expected without passive hydraulic fouling control. Although it was not possible to directly link the observed seasonal changes in TCP to potential seasonal changes in the biofilm microbiome, the analysis did suggest that the lower TCP during summer months was due to a greater microorganism richness in the feed and presence of filamentous, stalked, and biofilm-forming bacteria in the biofilm. Operation with higher trans-membrane pressure (i.e., ∼30 vs ∼20 mbar) and more frequent passive hydraulic fouling control (i.e., every 12 vs 24 h) enabled a greater flow to be sustained. The study demonstrated the long-term robustness and performance of GDMF with passive hydraulic fouling control for drinking water treatment.