Forward Osmosis

1. Forward Osmosis History, ancient and recent, & Some successful viable applications John O. Kessler, physics dept, University of Arizona, Tucson kessler@physics.arizona.edu

2. "Carchorodon megalodon, Helicoprion and Edestus"prehistoric practitioners of FO

3. And here’s a more recent expert in FO: Using seawater diffusing through semipermeable gill/mouth membranesas the source of fresh water

4. The basis of FO to the sharks’ blood: urea and triethylamine oxide (TMAO) • Like other sharks, the Great White's bodily fluids also contain small organic molecules. Among the most important of these from an osmotic standpoint are • urea and trimethylamine oxide (or TMAO, for short). Both urea and TMAO are nitrogen-containing break-down products of protein metabolism. Urea is highly toxic to living tissue at moderate to high concentrations, causing proteins to de-stabilize and thus cease to function properly or at all. That is why, although we can tolerate 'holding it' for a little while, we must eventually excrete urea or face dire physiological consequences. Yet sharks routinely retain bodily concentrations of urea that would kill most other vertebrates. This is largely due to the presence of even higher bodily concentrations of • TMAO, which counters the protein-de-stabilizing effects of urea. • Together, urea and TMAO add substantially to a shark's osmotic pressure, effectively rendering the internal fluids slightly (about 5%) 'saltier' than the external environment. As a result, sharks do not need to invest any metabolic effort toward obtaining the water their bodies need. A constant supply of fresh water osmoses passively into a shark's body • through the gills and other exposed membranes.

5. Dunaliella salina, a halophyte alga that uses synthesis of glycerol to match osmolarity of exterior salt concentration,even when it increases, e.g. due to evaporation. BUT, when the exterior salt concentration drops, Dunaliella can metabolize and/or discharge glycerol.

6. Dunaliella in sea water

7. Note crystal of salt: they can cope! Dunaliella produce glycerol and carotenes, the cause of reddish color in conc. brine ponds.

8. ?from sharks & algae to irrigation? _____________________________________________________ Tracing flow of ideas 1970 Sharks  Urea and action hmmm Fertilizer FDFO Have membrane? Fertilizer-driven forward osmosis Have brackish Together with Arizona agriculture needs: Conversion of brackish water to water usable for irrigation Chuck Moody Bob Riley Chuck Moody Bob Riley Unbacked cellulose acetate membranes

9. Well, it worked! Well, it worked! Then Chuck Moody went to Peace Corps. When he returned we renewed this R&D, with matching grant ($15K) from OWRT (office of water research and technology), and help from Univ Az VP Research, Dick Kassander

10. From FDFO to Sugar Pi • Using fertilizer solution as a driver: large scale application • What about powdered nutrient  FO Driving Solution? • Interesting: Calorie and water requirements well matched! • hmmmm~lifeboats, infiltrators, lost souls…… • SO inquiry at US Navy…..BUMMER! nyet.. no $$. • ( they said exposure bigger problem than thirst!!) __________________________________________________________ Oh well, on to science, efficiency, new applications

11. The next phase: problems, new approaches • Recyclable driving (=“draw”) solutes • Concentration polarization (boundary layers) • How to eliminate? Stirring? Flow cycles? • Membrane degradation, membrane design! etc, etc and etc! (and getting others, here, elsewhere to read about, notice our work!) Throughout Chuck Moody and Bob Riley have put in years of skill, hard work, insight and progress.