Mars Academy

Recyclying Water

Potable water is defined as water fit for human consumption.  There are several standards for potable water that need to be defined:

1. Microbiological:   coliforms
2. Physical:  turbidity, color, taste, odor, and temperature
3. Minerals:  dissolved and insoluble, hardness
4. Chemical:  acidity, alkalinity, dissolved gases 
5. Radiological:  alpha, beta, gamma contamination
   

(1)   Microbiological:  
There are several classes of microorganisms that are present in the human intesitine and feces, the most common of which is the pathogen E. coli.  Potable water is rendered safe and kept free from microbiological contamination by various disinfectants - most commonly chlorine.  However, chlorine is unacceptable in a space mission due to its tendency to form chlorine gas, which is toxic.  For this reason, iodine or silver may be used for disinfection or ozone bubbled through the water may be used as well.  It is also possible to use ultraviolet light or hydrogen peroxide.  Ultrafilteration is another possibility, employing filters with the capacity of filtering out all bacteria any many viruses.

(2)  Physical:
Potable water should be pleasant to the eye, free of coloration or solids, and without any odor.  Particulate removal is accomplished by multiple filteration techniques while activation carbon filteration serves best for odor removal.  Mechanical water treatment processes:
a) Multifiltration:  a system consisting of beds of sorbents and ion exchange filters
b) Reverse Osmosis:  a system consisting of a semi-permeable membrane through which     water is forced under high pressure.
c) Evaportion:  water is heated and vapor is collected as pure water

(3)  Radiological:    See Radiation  

(4)  Water requirements:  
Each crew member will require at least 26.2 kg of water per day.  Of that 5.26 kg/day will be used for potable uses and 29.3 kg/person/day for hygiene.
In order to overcome the need of water in this long-term mission in space, we will have to recycle water from showers, laundry and urine.  Our goal is to recycle all air, water, and solid wastes using mechanical and chemical processes as well as plants.  A biological bioreactor, a vacuum cleaner-sized device that relies on bacteria to remove organic waste from urine, laundry and shower water will be used.  Urine, however, will be processed separately through a more stringent filtration process than the waste water.  All the liquids will be run through a similar final purification step that will produce a water of high quality.  Iodine will be added as a final bacteria killer, giving the recycled water a distinctive alternative.