Water space settlement as a by-product of the air

Water is the most essential human need, hence providing enough water for the inhabitants is
a fundamental goal. Besides, water plays an important role in almost every agricultural and
industrial process. All of these require huge amounts of water daily, so the water management
has to be based on reusing and recycling, and to seldom be changed.
3.3.1 Water Production
As previously mentioned, it is desirable to renew the water aboard our spacecraft from time to
time in order to enhance the quality of water which is of such great importance to the citizens.
This action will be performed gradually, as new obtained water arrives to The Iris.
The main way to obtain water is by extracting ice from Moon’s crust. This process will be
carried out by robots, as explained in detail in Section 5.3.2.
Another way to obtain water is by reducing ilmenite, an ore that lunar soil abounds with.
Apart from water, this reaction forms a very useful product (Fe), and an expensive one, namely
titanium oxide:
FeTiO3 + H2 TiO2 + Fe + H2O12
Water can also be produced aboard our space settlement as a by-product of the air purification
processes in the industrial area, like the ones described in the previous section.
3.3.2 Water Recycling
We will use plenty of water purification methods so as to assure that water quality is at high
standards. The industrial zone will have a water supply system separated from that of the
residential and agricultural areas since they demand different water properties. Additionally,
production of drinking water and distilled water (used in the medical field) will contain extra
purification systems.
Microfiltration, Ultrafiltration, and Nanofiltration
All of these types of filtration are based on the same principles: water passes through a semipermeable
membrane that removes undissolved particles. The sizes of membrane’s pores vary from
0.1µm at microfiltration to almost 0.001 µm at nanofiltration. However, nanofiltration also
involves the applying of pressure (nearly 7 atmospheres) on one side of the membrane. These
methods will be utilized in every water supply system on The Iris.
Figure 34: Water filtration system comparison
Image Credit:
https://www.eurowater.com/products/standard products/nanofiltration plants.aspx
Reverse Osmosis
As the above graph shows, the reverse osmosis almost completely demineralizes water, thus we
can replace the classic and inefficient Ion Exchange method.
Osmosis is a naturally occurring phenomenon where a less concentrated solution tends to migrate
to a more concentrated solution. Reverse Osmosis is the process of Osmosis in reverse, and
requires applying of great pressure on the more concentrated solution, as illustrated in the
scheme below.
Figure 35: Reverse Osmosis
Image Credit: https://puretecwater.com/reverse-osmosis/what-is-reverse-osmosis
This method will not be used in the industrial area, in order not to make water too corrosive
and to enable us to obtain a certain hardness for each factory.
Although the filtration membranes don’t allow the micro-organisms through, it is mandatory
to also use a disinfection process in every water supply system in order to prevent any water
contamination . The ultraviolet disinfection is very effective, killing any pathogens, but it leaves
no residual disinfectant to inactivate the potential micro-organisms that may appear in the
distribution system. To tackle this problem, we will add chloramines during a second disinfection
step, whose residual disinfectants are long-lasting and don’t readily form trihalomethanes and
haloacetic acids13. This way, the negative effects of classic chlorine disinfection are avoided.