Longevity Aspects of Potable Water Disinfected by Ionic Silver: Kinetic Experiments and Modeling

Abstract

In the International Space Station (ISS), Russian and European cosmonauts drink water disinfected by dissolved silver. For this to be effective, the concentration of silver should remain above a certain threshold from the moment of its initial disposition in storage tanks on earth until its final consumption in ISS. Unfortunately, during water tanks transportation to ISS and during storage in ISS, silver concentration has been reported to decrease intensively beyond any reason. This work examines the effect of different materials used in ISS water storage and distribution systems on the reduction of silver concentration. An experimental campaign has been organized where passivated stainless steel (SS), passivated and electropolished SS and titanium alloy coupons (official ISS grades) are exposed to simulated ISS potable water at different silver concentrations, different surface to volume ratios, and at stagnant or flow conditions. The evolution of silver concentration remaining in the bulk water is recorded with respect to the exposure time. A reaction engineering model for the Ag loss to the coupons is developed. The model is fitted to the experimental data in order to derive the reaction rate expression and the corresponding parameters. For passivated SS and electropolished SS the silver deposition rate depends on the initial silver concentration in water but is rather unaffected by the progress of silver deposition on the surface. On the other hand, for Ti alloy, while silver deposition rate still depends on initial silver concentration, it decreases continuously as silver deposition on the surface advances, implying that Ti alloy surface becomes gradually saturated and so prevents further silver deposition. Such a model can be useful for material selection and design of water storage and distribution facilities for ISS.

A physicochemical model for rationalizing SARS-CoV-2 concentration in sewage. Case study: The city of Thessaloniki in Greece

“…Yet, there is some recent experience on the influence of environmental parameters against the action of biocides (due to adsorption, galvanic deposition, etc) in recycled hygiene and potable water samples under conditions prevailing in the International Space Station ( Petala et al, 2017 . Giakisikli et al, 2017 ; Mintsouli et al, 2018 ; Petala et al, 2020 ).…”

Investigation of Molecular Weight, Polymer Concentration and Process Parameters Factors on the Sustained Release of the Anti-Multiple-Sclerosis Agent Teriflunomide from Poly(ε-caprolactone) Electrospun Nanofibrous Matrices

“…In the case of mechanism (i), the length L is the slab thickness and α = 3 [35]. In the case of a sphere, L is the radius of the sphere and α = 15 [36]. In the case of the mechanism (ii) where the geometry is evolved from cylindrical to spherical, L is the fiber radius and α is approximately taken as 10.…”

Effect of surface treatment and shear flow on biofilm formation over materials employed in space water storage and distribution systems

“…Currently, the construction of space water distribution systems involves the use of various materials based on their unique properties and suitability to withstand the harsh space environment (Finckenor, 2018;Ghidini, 2018). Among them, metallic surfaces such as stainless steel (SS), either passivated or electropolished and titanium alloy (Ti-6Al-4V) are primarily used as construction material of pipes, junctions, etc (Petala et al, 2020). Regarding the preservation of water, NASA intends to utilize biocidal silver in order to ensure the quality of potable water and prevent the harmful effects of microorganisms (Petala et al, 2017).…”