Nutrient Recycling in Gebers Housing Project, Sweden

The toilets are urine separating toilets delivered by the company Wost Man Ecology AB (their "ES-Classic" model). The urine is flushed with 0,1 liters of water and runs by gravity to large tanks under the house for later transport to a farm where it is stored in very large reservoirs. Because of the natural rise to a high pH, urine is considered to be disinfected after 6 months of storage.

The feces are handled dry and fall straight down by gravity into individual bins under the house. This toilet system minimizes the volumes of the waste which is very important for the recycling. All nutrients, including potash and nitrogen are taken care of in this way. The urine is brought to the farm 3-4 times/year and is spread in spring to avoid leakage. The feces can be plowed under any time of the year because their low content of nitrogen.

The ventilation outlet from the bathrooms leads the air through the toilets, a system which takes away all odour even when the toilets are in use. It also improves the dehydration of the the feces which are stored under negative pressure. The storage is indivdual for each flat under the house. After one year the feces are taken out and composted collectively outside for later use in agriculture.

• The overall performance is satisfactory. Some problems have occured but I am firmly convinced that all the problems can be solved with better planning and management.
• Most of the problems are connected with urine sediments which are astonishingly voluminous - not only here but in all cases where urine diversion is used. Pipes tend to get clogged but are easy to clean. Hot water under pressure seems to be a simple way to clean clogged pipes.
• Watertraps should be avoided within the toilets and futher down all the way through the piping system to the urine tank. Watertraps are not needed because of the ventilation system.
• If so many toilets are connected, a diameter of 110 mm for the common piping is recommended. Even slope in the pipes without extra watertraps!
• With a common ventilation system for many families fly barriers should be used. These should be placed in a way that they can be cleaned easily.
• Good installation instructions for the plumbers are necessary, since they usually are not familiar with this kind of system.
• The intervals for emptying the boxes for the feces may be shorter than 6 months to prevent eventual fly invasions.
• All toilets, even on the ones on the second floor have the bin for the feces in the basement. The investment costs would have been lower, if toilets with an integrated collection bin had been used (such as "WM-Thrones" or "WM-Privvies").

• No anthropogenic nutrient export to surrounding water bodies.
• An average water consumption of 110 Liter / person / day in the houses, which is considered very low in Sweden.
• The sanitation fees from the community are expected to be reduced.
• Farmers can save fertilizer which saves energy. However, on the market, fertilizer is cheap and, according to the EU, "ecological” farming is just now not allowed to use any human waste. I think the farmers have to be paid for the time beeing.
• Probably no energy saving in the house.

In reality, the total investments costs for the urine system were 15'000 USD. The system for the feces (including the ventilation system) became very expensive, due to tough conditions from authorities concerning fire safety. This gave very high consulting costs. A solution based on WM-Throne or WM-Privvy would have been much cheaper.