EcoEng Newsletter No. 12, June 2006

Towards the sewerless city

First experiences from a full scale Ecosan pilot project at SolarCity, Linz, Austria
Content No. 12/06
  Title page / Index
  Water from the well
  Phototrophic biofilms
  optimising waste flow
  India: Water supply
  schemes in a slum
  Austria: Sewerless city
  Composting: Ch. 5
  PNG: Ecosan project
  Biopros project
  Ecosan curriculum CD
EcoEng News:
  Joe Swamp
Various issues:
  IEES Writers' Fund
  Mailing list
  EE-Newsletter Flier

by Andreas Schoenborn

EcoEng-Newsletter co-editor
armadillo media
PO Box 2116
CH-6002 Luzern


Ecosan - the change of paradigm is still ahead

Fig. 1: Appartments of GIWOG at SolarCity, where urine separation toilets are installed
Source of photo: see references

Ecological sanitation has the potential to revolutionize the way we deal with human waste in the future. This is clear to all that work with the approach - however, it isn't quite as evident to the rest of the world. In the heads of many influencial persons, the change of paradigm is still just starting.

An important reason for this may be, that ecosan is still associated with small settlements, isolated summer houses, rural farm settings, or with development of poor areas in developing countries. Also, in densely populated cities ecosan mostly competes with an existing wastewater infrastructure. There still is a lack of practical on-site experiences with medium to large scale ecosan pilot projects. There are also still safety concerns regarding the use of human feces and urine.

In the city of Linz, Austria, the currently largest European pilot project using urine separation toilets was started in 2004. As part of the development area SolarCity (about 1300 appartments), located in Linz-Pichling, urine separation toilets were installed in 88 appartments and in a public school. It should be mentioned, that the human waste concept is just a part of the innovative ideas that were implemented in the SolarCity.

From the pilot, the responsibles at Linz AG are expecting results for future development of innovative wastewater systems in densely populated areas. On Feb. 28, 2006, Dr. Horst Steinmüller of Linz AG presented first results from this pilot to an interested audience at EAWAG Duebendorf, Switzerland.


Details of the ecosan concept implemented at SolarCity, Linz


In the 88 appartments and the school, urine and black/greywater have been collected separately since 2004, using separation toilets built by Roediger. For urine, a collection system is in place. Black- and greywater will be treated in a compost filter, followed by constructed wetlands, to be built this summer (2006). Ultimately, the urine should be reused in agriculture while the treated black and greywater should be discharged to a nearby stream. The material from the composting filters will be composted and reused in horti- or agriculture.

The whole reuse-part of the system, however, is still only a plan. The legal framework in Upper Austria still poses two severe problems to the project: 1. The Upper Austrian soil protection law does not allow the spreading of human urine on soil. 2. The law on wastewater disposal demands a centralized collection of wastewater in densely populated areas. Both laws put the whole concept in question.

The responsibles at Linz AG decided to be pragmatic. Currently all collected urine and all the treated wastewater is sent to the sewer, only to be treated again in Linz's big central wastewater treatment plant. "We are trying to see the advantages", Steinmüller said with a smile. Now they can experiment at their leisure without having to obey the Austrian discharge legislation. The setup allows to run the system in various ways. E.g., urine can be added to the wastewater - to add nitrogen -, the constructed wetlands can be run with varying wastewater loads, different types of composting filters and other pretreatment systems can be tried out. A true pilot, so to speak.

While producing results and with their help, Linz AG hopes to find a solution with the authorities that will ultimately allow to implement urine reuse and wastewater discharge.


First results & feedback

 Fig 2: Public school and nursery at SolarCity, Linz, Austria
Source of photo: see references

Having the above mentioned limitations and the incomplete state of the wastewater system in mind, it is evident that the performance of the toilets is really the only part of the system that allows some first conclusions. After almost two years of operation, a survey about the toilet performance was conducted.

The 88 appartments equipped with urine separation are inhabited by, as Steinmüller termed it, "normal average of Linz's younger population". Only 10% of them moved in because of the pilot project. Therefore, the group of users can be seen as more or less representative.

From about 60% of all appartments the filled out questionnaires were returned. User satisfaction about the toilets in general was good - some liked it, some disliked it, most were indifferent. An almost Gaussian distribution, as Steinmüller said. Only 11% reported problems with the toilets, most of which were due to wrong operation and could easily be solved by informing the inhabitants better.

The most interesting result of the survey was, in my view, that 77% thought the toilets could be improved. Many took the chance to propose improvements, often related to design issues. This clearly highlights that not only the whole system, but also the toilets themselves are still under development and can be seen as prototypes.

Some unexpected and even funny problems occured in the public school: In the toilets installed for grades 1 and 2, urine separation did not work properly, resulting in nuisance by odour. The reason: The toilets are simply too big for small children. Feces goes to the urine part of the toilet and is not flushed away properly from there, which leads to the typical stench of an uncleaned toilet. The special toilet seats that can be bought for small children - all parents will know what I mean - are not made for urine separation toilets and direct the feces to the wrong place, too.

Another fact is that technical devices installed in schools need to put up with some explorative assaults by curious school kids, to say it nicely.


Open questions


A big, yet unsolved question of this type of ecosan approach is how the safety of the final products, urine fertilizer and fecal compost, can be reached. If you are sick and swallow some medication it will ultimately end up in the urine, either as the original substance or as a metabolite. Human urine also contains hormones like estradiol or testosterone. Last but not least, there are substances from our food, such as caffeine.

Remainders of pharmaceuticals or traces of endocrine hormones (e.g., estradiol) in urine fertilizer can potentially interfere with organisms in nature, when the urine is released. This is not different to flushing it away to a wasterwater treatment plant. But the concentrations will be much higher in a urine fertilizer.

A number of questions arise from that:

  • How big is the risk these microcontaminants really pose?
  • How will they behave in nature, e.g., in soils?
  • How can they eventually be removed from the urine?
  • What are the relevant substances among the hundreds of different pharmaceuticals, hormones etc.?

An in-depth literature research funded by Linz AG is currently conducted at the Technical University of Hamburg-Harburg, Germany, aiming to build up a database of information about the behaviour of microcontaminants in wastewater, in WWTP and in nature. According to Dr. Steinmüller, it is their vision to allow access to this database also for other institutions. So far, about 70 papers have been analyzed.

Parallely, Linz AG seeks cooperation with universities and institutes to develop suitable technologies for the removal of microcontaminants from human urine. The experiments are still at the stage of lab-scale trials. Here, a larger network of contributors would certainly be of help.


Some personal remarks


The project at SolarCity is mostly financed by Linz AG, a large public service company, providing energy, telecommunications, transport and community services - basically every public activity in Linz (including swimming pools and public transport) and among many other things the local WWTP for about 950'000 PE.

Why would such a company engage in an ecosan pilot project? Considering their mere size, it is obvious that they can do it without stretching their bounds. According to Steinmüller, Linz AG sees this as part of its resonsibility towards society, being the second largest public service company in Austria.

This positive attitude towards rather new and still visonary ideas is remarkable to me. I like it and I wish we had more companies like them. Ecosan technologies have just done their first steps to becoming serious competitors. There's still a long way to go.




SolarCity Linz, general:

SolarCity Linz, disposal: [in German]

Linz AG:

Plan of SolarCity (in English):

Roediger, Separationstoiletten Ecosan:

Roediger Home:

Source of photos:

© 2006, International Ecological Engineering Society, Wolhusen, Switzerland