This is part of my generation ship worldbuilding. I mentioned my water purification system in a different question, but I never directly asked about it. Here, I will directly ask about it. I think it will make more sense if I go step by step through the water purification process, starting at the input.
Here are all the things that are input into the system:
- Wasted water
Stage 1: Solid filtering
The wasted water will just move on. The rest of it though goes through the solid filtering system first. Solid poop and any solid menstrual contents won't pass through. Everything else will, leaving behind:
- Wasted water
- Stomach acid
Stage 2: Gradual filtering
At this point, the contents reach a series of microfilters and nanofilters of finer and finer mesh. To make sure that the water doesn't get blocked, the finest filter is no smaller mesh than a urea molecule. Here are the average sizes of what would be filtered out:
- Blood cells: 6-8 micrometers for RBC's, 2.6-2.9 micrometers for platelets
- Bacteria: .2-2.0 micrometers
- Viruses: 20-200 nanometers
- Protein: 53kDa
- Urea: can't seem to find size for, but is definitely bigger than water
All that is left in this stage is stomach acid and water.
Stage 3: Acid Base Reaction
This is the stage that gets rid of the stomach acid. The acidic water goes into a pH correction tank. In there are a few wires, a valve, a sensor, and a dispenser. To avoid toxicity, I chose my base wisely. The sensor is calibrated for high acidity. When all that is left is acidic water and the acid is hydrochloric acid, the pH is anywhere from 1-2 depending on how much acid there is. This is way too low for some water to be drinkable.
When the sensor senses an increase in acidity, it electrically activates the base dispenser. To avoid acid corrosion, the wires are made out of either gold or platinum. Since there is no nitric acid present, there is no way the wires would dissolve, unlike how they would if they were made out of say copper. Gold is a way better electrical conductor than platinum, so the wires would most likely be made out of gold.
Here is the acid base reaction that occurs in the pH correction tank:
HCl + NaOH → H2O + NaCl(aq)
This is what the reaction looks like:
The valve is also unable to corrode in hydrocholoric acid, just like the wires. Once the pH gets to 7, the base dispenser is deactivated and the valve is opened. This leaves behind saltwater, very close to the final product.
Stage 4: Desalination
Now, to get rid of the salt, the water is repeatedly boiled and condensed. This leaves behind pure water and solid salt as byproducts. The salt is then stored and the water is ready to be used again. Since there is more water produced than was there at first after the acid base reaction, there should be no issues with the generation ship running out of water.
Will this water purification system work at both providing a constant supply of water and making sure that it is completely safe to drink? Or would the water get blocked up at the fine filters?