Tuesday, November 18, 2008
The shuttle carries two new sleeping compartments and a water recycling system that will enable the crew to purify urine and other wastewater for drinking.If NASA wants to go further down this path, it should consider giving a research grant to the Academy of Lagado, which is well known for its work investigating such methods of recycling:
"We did blind taste tests of the water," said NASA's Bob Bagdigian, the system's lead engineer. "Nobody had any strong objections. Other than a faint taste of iodine, it is just as refreshing as any other kind of water."
"I've got some in my fridge," he added. "It tastes fine to me."
NASA expects to process about six gallons (23 liters) of water per day with the new device. The goal is to recover about 92 percent of the water from the crew's urine and moisture in the air.
The wastewater is processed using an extensive series of purification techniques, including distillation which is somewhat tricky in microgravity filtration, oxidation and ionization.
The final step is the addition of iodine to control microbial growth, Bagdigian said.
The device is intended to process a full day's worth of wastewater in less than 24 hours.
"Today's drinking water was yesterday's waste," Bagdigian said.
I went into another chamber, but was ready to hasten back, being almost overcome with a horrible stink. My conductor pressed me forward, conjuring me in a whisper "to give no offence, which would be highly resented;" and therefore I durst not so much as stop my nose. The projector of this cell was the most ancient student of the academy; his face and beard were of a pale yellow; his hands and clothes daubed over with filth. When I was presented to him, he gave me a close embrace, a compliment I could well have excused. His employment, from his first coming into the academy, was an operation to reduce human excrement to its original food, by separating the several parts, removing the tincture which it receives from the gall, making the odour exhale, and scumming off the saliva. He had a weekly allowance, from the society, of a vessel filled with human ordure, about the bigness of a Bristol barrel.Jonathan Swift, Gulliver's Travels.
Thanks to Jim K., who draws my attention to Dana Cordell, The Story of Phosphorus (footnotes omitted):
Human excreta (urine and faeces) are renewable and readily available sources of phosphorus. Urine is essentially sterile and contains plant-available nutrients (P,N,K) in the correct ratio. Treatment and reuse is very simple and the World Health Organisation has published 'guidelines for the safe use of wastewater, excreta and greywater'.
More that 50% of the worlds’ population are now living in urban centres, and in the next 50 years 90% of the new population are expected to reside in urban slums. Urine is the largest single source of P emerging from human settlements.
According to some studies in Sweden and Zimbabwe, the nutrients in one person's urine are sufficient to produce 50-100% of the food requirements for another person. Combined with other organic sources like manure and food waste, the phosphorus value in urine and faeces can essentially replace the demand for phosphate rock. In 2000, the global population produced 3 million tonnes of phosphorus from urine and faeces alone.
Unlike phosphate rock, which only exists in a handful of countries' control, urine and faeces are available from any community or city,and hence can contribute to 'phosphorus sovereignty' and food security.
In material flow terms, human excreta represents a readily available 'exchange pool' of phosphorus, before it is 'lost' to the hydrosphere typically as treated or untreated effluent discharged to rivers and oceans. If urine is reused as a fertilizer, then less phosphorus (in urine) is entering waterways, reducing the potential to cause toxic algal blooms.
Although preventing phosphorus point sources from entering water bodies is often necessary to prevent water pollution, removing high levels of phosphorus at the wastewater treatment plant is expensive and energy intensive. Capturing urine at source (at the toilet) can be much more energy efficient and cost-effective and does not contain heavy metals like Cadmium.
The cost of ecological sanitation systems around the world could be offset by the commercial value of the phosphorus (and nitrogen) they yield in the future. Particularly in Africa where synthetic fertilizers typically cost 2-5 times more than in Europe. A community ecological sanitation toilet in Tamilnadu, India, now pays users, recognising the fertilizer value of their urine and faeces.