Membrane Contactors - to recover potable water from wastewater in space

Membrane contactor technology has been demonstrated in a range of liquid/liquid along with gas/liquid software in wastewater therapy, fermentation, drugs, chiral separations, and semiconductor creation, material ion removal, and protein removal.

 These are functionally similar to continuous contact mass transfer devices like forced draft aerators or vacuum towers.

 Even some kind of long-term human missions in space require a continuous and self-sufficient supply of fresh water for consumption, hygiene and maintenance. In these type of missions the sources of wastewater is hygiene wastewater, urine and humidity condensates.

 To satisfy these concerns and other requirements there should be one equipment or technology or process required. Similarly the process is needed to be cost effective, efficient and lightweight. There is one equipment or process called membrane contactors which usually satisfy almost all above needs can be acquired.

 This Article will describe about this equipment or process used for this purpose and also explains which are the techniques, procedure and applications in different fields.

 Introduction

 Membrane contactors are devices that allow a gaseous phase and a liquid phase to come into direct contact with each other, for the purpose of mass transfer between the phases, without dispersing one phase into the other.

 Membrane contactors are manufactured with hydrophobic hollow-fiber microporous membranes. The hollow fiber wall is very thin (25-100 micron) and highly porous. Hydrophobic nature of membrane will hold the water, and the force required for water to enter into membrane pores is calculated through Young-Lapace equation.

 Membrane contactors can be made from following materials

• Polypropylene
• Polyethylene
• PVDF
• PTFE
• PFA
• ABS
• Polyvinyl chloride
• FRP
• Stainless steel

 Young-Lapace Equation

Young-Lapace equation explains capillary pressure difference sustained across the interface between two static fluids, such as water and air.

δP1  = σ(1/R1 + 1/R2)

 Where

δP1    - pressure drop

σ     - Surface tension

 By watchful control of the pressure difference relating to the fluids, one of the fluids is usually immobilized inside pores of the membrane in order that the fluid/fluid interface is found at the particular mouth of each one pore.

 This approach offers quite a few important benefits over typical dispersed phase contactors, including absence of emulsions, zero flooding from high stream rates, unloading from low stream rates, density distinction between body fluids required.

 Indeed, membrane contactors typically offer thirty times additional area than what's achievable in gas absorbers in addition to 500 times what's obtainable in liquid/liquid removal columns, leading to remarkably reduced height of a transfer unit (HTU) values.

 Membrane contactor’s primary function is recovery of potable water from wastewater and secondary functions include oxygen reconstitution and humidity control systems.

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