Lightweight Contingency Water Recovery System Concept Development 2008-01-2143
The Lightweight Contingency Water Recovery System (LWC-WRS) harvests water from various sources in or around the Orion spacecraft in order to provide contingency water at a substantial mass savings when compared to stored emergency water supplies. The system uses activated carbon treatment (for urine) followed by forward osmosis (FO). The LWC-WRS recovers water from a variety of contaminated sources by directly processing it into a fortified (electrolyte and caloric) drink. Primary target water sources are urine, seawater, and other on board vehicle waters (often referred to as technical waters). The product drink provides hydration, electrolytes, and caloric requirements for crew consumption.
The system hardware consists of a urine collection device containing an activated carbon matrix (Stage 1) and an FO membrane treatment element (or bag) which contains an internally mounted cellulose triacetate membrane (Stage 2). All components are light weight disposable plastic, the system is potentially wearable, and it uses no electrical power. When treating urine and other wastewaters containing high levels of organic contaminates this two stage treatment process is required. Seawater and wastewaters containing low levels of organics can be treated for removal of inorganic contaminants (like the salt in seawater) and microorganisms using only the second stage FO membrane element.
First year performance testing indicated acceptable flux rates and water recovery percentages over 6 to 12 hours of optimal urine treatment, when using the full system. Some challenges remained in achieving and evaluating acceptable contaminates flux/rejection rates for TOC and nitrogen species in the product; see ICES paper 2007-01-3037 (Gormly and Flynn, 2007). Year 2 work has focused on four basic areas:
Characterizing performance of the Stage 2 FO membrane treatment to harvest seawater for use in post landing survival at sea.
Researching alternative food product and components for use as the osmotic agent (OA).
Pursuing better TOC confirmation in terms of total expected flux/rejection and characterization. In particular, research to confirm (TOC) flux measured in NaCl/ultra-pure water brine product solutions using high chloride compatible analysis methods.
Increased nitrogen species control and characterization in the process and product, particularly investigating product side options for urea and/or ammonia nitrogen control.
Of these tasks the first is complete, the second and third are in work with substantial data currently available and reported, and the last is in the initial stages of concept development and data collection.
Concluding comments and discussion will include a synopsis of seawater, urine and technical water recovery concept development as well as some future options for developing this technology. Initially, the system's urine recycle function is intended for contingency/emergency use only, but will do so at a significant mass savings when compared to contingency water supplies and/or conventional water treatments. LWC-WRS Stage 2 can be exploited to provide emergency utilization of seawater and technical waters. Ultimately, further development of the technology may also provide options for better integration of water recycling into larger habitat component design by including FO membrane elements within the structures.