Dialysis-based Passive Biocide Delivery System: An Exploratory Analysis on the Development of a Silver Dosing Alternative for Spacecraft Potable Water Systems

Abstract

This paper describes the use of a dialysis-based passive dosing system for silver ion delivery as a biocide for potable water systems in spacecraft and extraterrestrial bases. A silver dosing device has been developed for continuous water treatment, based on the International Space Station Water Processor Assembly framework. The Passive Biocide Delivery System is designed to supply a stream of product water with silver ions at a concentration range of 200-400 ppb, using a membrane to control dosing. Potable water with these silver concentrations can be safely consumed by humans. The dialysis approach is attractive since it does not require additional energy nor high pressure to function. Computational Transport Phenomena has been implemented to study the performance of the membrane setup at particular operational conditions and guide the choice of membrane properties. The results suggest that the dosing device can release silver ions at the target levels for at least eight hours without excessive silver salt consumption. This paper contains technical background and preliminary results from the Passive Biocide Delivery System development and presents the benefits and challenges of its implementations in spacecraft and Lunar/Martian bases.