Evaluation of the freeze-thaw behavior of polysulfone hollow-fiber membranes

The continuous delivery of drinking water to military field personnel presents a serious logistical challenge. Each soldier requires an uninterrupted supply of 1.5 to 3.0 gallons of water per day to prevent dehydration. Local water sources may be available but they may be contaminated with indigenous pathogenic organisms, chemical or biological threat agents. Presently, the military has identified an IWP filter with a low enough pressure drop to allow a soldier to drink directly through a reasonably sized filter without undue effort; however, the present filter can not maintain its initial performance after freezing and thawing cycles. Current research suggests that the mechanism of damage is not rupture due to the expansion of the water as it freezes but mechanical damage done by ice crystal growth. The objective is to evaluate the freeze behavior and confirm the failure mode of an IWP filter subjected to freezing and thawing to develop a “practical” solution. The most successful methods will increase the weight and bulk the least and not require any additional consumables. It will not make the resultant system heavy and bulky as to negate the weight and size advantage of the hollow-fiber filtration media.