If you live in a developing country you use 10 liters of water a day. A European uses 200 liters and an Ameican 400 liters. A third of this is drained into the toilet! A family of five uses 1 m3 per day. A typical European toilet uses 4—12 liters pr. push, American 20 liters.
The water closet accounts for 20-40 % of water use and is an anachronism. It would probably not have been allowed if introduced today.
Figures from Water Supply and & Sanitation Collaborative Council, UN, Stocholm Environment Institute.
1.3 billion people experience lack of clean water, and 2.4 billion people will be lacking sanitary facilities by 2015. (The International Decade for Action, Water for life 2005-2015, UN)
We will hav a shortage of water for 30 % of the world population in 50 countries by 2025.
Toilet drain also carries away nutritients like phosphorus, potassium, nitrogen that are used for food production. Phosphorus is not sustainable and could be hard to find in 100 years time, instead ending up at the bottom of the sea where it is difficult to reclaim.
Urine is very rich in phosphorus, is sterile and well suited for food production. 15-20% of the fertilizer we use now can be replaced by runoff water containing urine.
Urine has been used as fertilizer in many countries already. Theoretically all food for the world could be grown by using runoff water from toilets. Recirculation of toilet water is possible by toilets that separate urine and excrements. This can be done by vacuum toilets using 0,5-1 liter.
In Mongolia (Dongsheng), Norway (Oslo) and the Norwegian Environmental University installations are in place.
