In South Africa researchers from Eawag have worked with local authorities to build an inexpensive system which improves the hygiene in the settlements, reduces the contamination of the water resources, and produces a fertilizer for agriculture. The raw material used for this is urine. The system would also be suitable for use here in Switzerland for stadiums, railway stations or motorway service areas.

In the language of the Zulus, who live in the Durban region, “Vuna” means harvest. In fact, VUNA is also the abbreviation for “Valorisation of Urine Nutrients in Africa” − a project that Eawag has set up with financial assistance from the Bill & Melinda Gates Foundation. Process engineer Bastian Etter has been on location supervising the project for the past four years: “Durban is a very mixed type of town with skyscrapers, eight-lane highways and exclusive residential quarters, but also slums and scattered settlements spread across a very hilly region”, he says describing the metropolis by the Indian Ocean on the east coast of South Africa. “But above all, Durban is very progressive.” So VUNA also stands for a success story, showing how the transfer of technology can be of benefit for all those involved.

Ten years ago Durban saw a period of extremely rapid growth, and suddenly it had three million residents, but no proper waste water facilities to cover the extensive settlement zone. After the end of apartheid in South Africa, the right to have a WC was given a legal basis in the new constitution, and so the authorities decided to install waterless toilets. In the outlying areas of Durban there are now 90,000 WC huts with toilets that do not have water to flush, and where the excrement and urine are separated. The solids are dried and buried, but the liquid excretion seeps down through the ground in most places, and so in the long term it pollutes the streams, rivers and groundwater. However, in the case of some 700 families who are participating in VUNA it is quite a different story. For these people, the council workers come and col lect the urine in canisters so that it can be further processed and used.

The researchers supply the raw material themselves

“Urine is a resource”, says Kai Udert, VUNA project leader at Eawag. “We eliminate 50 to 90 % of the nutrients not in the solid matter, but in the urine.” This includes nitrogen, potassium, sulphur and phosphorous, as well as trace elements like boron and manganese. And this is where the Eawag scientists come in, because the processing of urine is their special field of expertise. “We bring the best expertise in process engineering from Switzerland to South Africa”, says Kai Udert. A number of experts at Eawag also contributed to the project. Besides the environmental chemists and social scientists, specialists in automation and data modelling are also on board.

In the main building of Eawag in Dübendorf the staff provided the raw material for the Swiss test plant themselves by using the NoMix toilets. In the cellar of the building, there are two large black tanks in which the liquid from the WCs located above is collected and stored. In the room in front there are plastic columns about two metres high – these are the reactors. In these, thousands of bright little plastic particles are bubbling away in a brown fluid. In the first stage, the nitrogen, which is found in urine in the form of pungent-smelling ammonia, is stabilised in these reactors. This work is done by bacteria that sit on the plastic particles. This is the activated sludge of sewage treatment plants. But while that process works automatically in diluted waste water, here the researchers first have to teach it to the tiny living organisms in their pilot plant: “The concentration of urine in our reactor is much higher than in the usual sewage treatment plant”, says Kai Udert. “So we have to gradually feed the bacteria and add a little more urine each day, until after two months they are able to process the high concentration levels.” In this way, a solute of odourless ammonium nitrate is produced, replacing the volatile ammonia.

Full bloom in the office

In a second stage, the ammonium nitrate solution is fed into a distillation plant. This is set up in the same room, right next to the reactor columns, and it extracts 97 % of the water. What is left is a brown liquid that contains the nitrogen compound and also the other nutrients. “This is a fertilizer, just like those you buy in the supermarket or at the garden centre”, says Bastian Etter as he opens a full bottle. In fact the unpleasant urine smell really has disappeared. The processing engineer describes how he uses it to water the plants in his office. He relates how, since he started doing this, the chilli plant in one pot has grown a lot more pods, and another plant is blooming better than ever.

After finding that the two reactors worked well in the first test in Dübendorf, the researchers went on to build the same installations in South Africa, in collaboration with the Durban University of Technology. One reactor was installed in the middle of Durban, in the modern customer centre at the waterworks. “This shows the commitment of the town authorities”, says Bastian Etter. It is also meant to demonstrate that the new technology is suitable not only for the slums, but also for the high-rise buildings in the dense city centre, thus promoting the acceptance by the populace. Surveys showed that the collection of urine was hardly ever rejected for cultural reasons. The people's expectations were more problematic, explains Kai Udert: “Many people just want water-flushed toilets because of the prestige, and they think the town is obliged to meet their demand.”

Another point is that many of the newly erected WC huts tend to break quickly, because of poor quality of manufacture, and this hinders the collection efforts. However, one positive effect is how the authorities are trying to inform the people. “Experts go to the suburbs of Durban and explain to the people what hygiene can do”, narrates Bastian Etter, as he praises these efforts. “They are really making an effort here.” They also explain how one can obtain valuable resources from urine. “This makes the system more attractive.” Researchers at the ETH Zurich are also investigating the idea of offering additional incentives by paying the inhabitants a subsidy if they collect and deliver the urine themselves.

Residue of medicines in the fertilizer

Some questions still need to be addressed. “While urine is very pure, it is not completely sterile”, says Kai Udert. Most of the pathogens are excreted in the faeces, but a cross-contamination of the urine can take place. Researchers at the EPFL checked to see if bacteria and viruses could be destroyed during the fertilizer production. One effective method to destroy the germs is distillation, as the urine is then heated to 80 degrees. In fact, besides pathogens the urine may also contain traces of medicines. “This is a major issue in South Africa because of HIV”, says Kai Udert. Measurements in Durban showed significantly higher concentrations of antibiotics and antiretroviral substances than those found in comparative analyses in Dübendorf. We do not yet know whether this will be a problem, the expert says. But he is confident that valorisation of urine is definitely worthwhile: “This met hod allows us to eliminate the pollutants much more effectively.”

The researchers are now looking for new partners who are willing to build and sell the reactors. The technology is not only suited to countries where the water management in the settlements is inadequate. “There is a lot of potential in Europe as well”, says Bastian Etter. In Switzerland, the Federal authorities are planning to issue a new law requiring that phosphorous in effluent sludge is recycled. From the standpoint of process engineering, the experts argue, it would also be logical to reclaim the nutrients at the place where they are first produced – that is to say in the urine – even though our liquid excretions only wash out half of the phosphorous.

The valorisation of urine would be particularly effective in places where there are already waterless toilets, for example in sports stadiums. But also at motorway service areas and in railway stations, where large quantities of urine have to be managed, the production of fertilizer could be economically viable. The foundation for commercial use of the technology has been laid by VUNA. “We were able to learn a lot when setting up the project in Durban with our South African partners”, notes Bastian Etter.