A Novel Method to Quantify Real-Time Compaction of Water Treatment Membranes

Membranes play critical roles in seawater desalination, wastewater treatment, potable water reuse, and resource recovery. Their performance can be adversely affected by compaction, which can limit their practical use and durability. While previous studies have employed scanning electron microscopy to measure thickness before and after compaction, real-time compaction measurement has not been possible. This study introduces a novel method to quantify the compaction of membranes under low pressure (up to 12.5 psi) by combining electrical impedance spectroscopy with dynamic mechanical analysis. Short- and long-term mechanical tests were conducted to investigate instant compaction, creep, recovery, and hysteresis. The method was validated using in situ and ex situ measurements. Results indicate that the initial instant compaction (98% of total compaction) contributes more to total compaction than subsequent instant compaction (from 83 to 67% of total compaction). The ratio of creep to instant compaction is introduced as a key indicator of material resilience; its increase from 2.4 to 49% indicates that as pressure increases, creep contributes more to total compaction. While limited to low pressures and a dry testing environment, this novel method shows promise for detecting and predicting performance and fatigue of water treatment membranes in various applications.