As pointed out earlier the treatment of waste water is essential for the quality of live in space settlements. Waste water is full of substances which need to be removed from it, before it could be converted back to drinking water. In particular waste water is rich in nitrates and ammonium.
Certain bacteria could be used to remove these nitrogen-based substances from waste water. The recovery of nitrates and also of phosphor from waste water, would be useful for the production of manure – to be used by farmers.