An overview of initiatives in Europe to recover phosphate from source
separated urine.
J.A. Wilsenach
Delft University of Technology, The Netherlands
J.A.Wilsenach@tnw.tudelft.nl
Phosphate rock is a limited natural resource and is in some instances contaminated with
heavy metals. Human urine is a potential source of phosphate. It could be used as
fertiliser or phosphorus can be removed (e.g. by crystallisation) as a secondary raw
material. Around 50% percent of the phosphorus in municipal wastewater originates
from urine. Whereas phosphorus in wastewater is present in low concentrations of
around 8 mg P/, the concentration in undiluted urine is around 800 mg P/. However,
there are many conditions before phosphate can be reclaimed from source separated
urine.
There have been many applications of human or
animal urine in history. The historical cycle
between agricultural produce and animal and
human excreta is well known. Less well known is
the use of urine in the textile industry to wash and
dye wool in the Dutch town Tilburg. Workers had to
bring their own urine in flasks to the factories (refer
picture). A book dating back to 1822 describes
processes where the addition of “buckets of urine”
is mentioned. At that time, urine was sold for 5c a
bucket. Of course the logistics, industrial scale and
people’s perceptions make similar practices
inconceivable today.
In the following paragraphs, a few modern European initiatives to collect urine
separately, with the potential of phosphate recovery, are discussed. The Dutch
foundation for applied water research (STOWA) is funding a study to investigate
possibilities of reclaiming minerals from municipal wastewater. A part of this study is the
compilation of an inventory containing information on different projects in this filed.
These projects (initiatives) are often more concerned with improving the total water cycle
and developing more sustainable wastewater treatment technology than with reclaiming
phosphate per se.
1.
Scandinavian initiatives
Sweden was the first country to manufacture modern urine separation toilets on large
scale. Several of these toilets were installed during the last decade.
1.1
Ecological villages
Definitions of a concept such as “ecological village” may vary considerably. In these
instances (discussed below) the concept implies inhabitants who adopt a way of living
that is deliberately changed from modern urban habits towards a more sustainable
lifestyle.
Björsbyn ecological village was built in 1994, 5 km north of the Lulea city centre
(Northern Sweden). It consists 17 houses (55 people) with urine separation toilets. Urine
is collected in tanks before being sprayed on farmlands near the village. Faeces goes
trough a septic tank and the sludge is composted and applied to grazing fields. “Grey
water” infiltration failed during winter due to freezing. During the study period, less than
half of the expected nutrients were recovered. This is due to problems such as leakage,
design of toilet and precipitation in pipes (pH = 8-9). Based on data from interviews, it
can be assumed that about 70% of the toilet visits occurred at home. Minerals recovered
from urine were approximately 3.3 g N/pe.d and 0.17 g P/pe.d, but some of the nutrients
will be found in the septic tank sludge. Water volumes needed for flushing urine were
higher than expected (due to poor toilet design) and lead to dilution of recovered
nutrients.
(Hanæus, Hellström, Johansson, 1997)
Understenshojden ecological village, within the city of Stockholm, has 44 apartments
with 160 inhabitants. All urine was separated at source and piped to two large collection
tanks. Quantities of the collected urine was close to that expected. 4.9 g N/pe.d, 0.42g
P/pe.d and 1.34 g K/pe.d were measured, which implies that around 50% of the minerals
in urine were not collected. It was expected that the remaining 50% would be excreted
away from the village, at offices or public places. Local organic farmers collected the
separately collected urine to spray it on their fields. Around 50% of toilet flush water was
saved with separation toilets. Urea rapidly dissociated to ammonia and carbon dioxide
and the pH increased to nine (measured in storage tank). This would have been an ideal
environment for phosphate crystallisation, of which no mention was made. It is uncertain
why this did not happen (in which case the measurements might have been different). It
should be noted that at high pH, ammonia evaporates, which means that much of the
nitrogen would be lost when sprayed on fields. Contamination of separated urine by
faecal material was very small.
(Jönsson, Stenström, Svensson and Sundin, 1997)
Munkesogaard ecological village, Roskilde (Denmark), consists of 20 houses with urine
separation toilets. The urine is piped to a central tank and collected by local farmers to
spray on their lands.
1.2
Research initiatives
A number of individuals are concerned with aspects of urine separation technology:
Jönsson et al, 1998, “Modelling the sewage system - evaluating urine separation as a
complementary function to the conventional sewage system” The study argues that
separation of urine and direct re-use as fertiliser is more energy efficient than the total of
removing nutrients in treatment plants and production of industrial fertiliser. Results
indicate that urine separation leads to decreased eutrophic effect, when compared to
conventional wastewater treatment where 60% of nitrogen is removed.
Hellström & Kärrman (1997) offered a comparative analysis of chemical exergy in
wastewater. Exergy can be defined as the useful part of energy that can perform
mechanical work. Inputs and outputs within three alternative wastewater treatment
systems were evaluated on basis of exergy. The three systems are: (1) conventional
using sludge as a fertiliser; (2) conventional framework, using sand filter beds, sludge as
a fertiliser and bio-gas production; (3) source separation using filter beds for treating
grey water only, faeces are used for bio-gas production and fertiliser and urine is
separated for fertiliser use.
Hellström, 1998, “Nutrient management in sewerage systems: investigations of
components and exergy analysis” The study presents results from different experiments
to improve nutrient management in sewerage systems. An exergy analysis showed that
urine separation technology might be a better alternative to conventional wastewater
systems. Hellström assumes that all collected urine can be used as fertiliser and
excludes the exergy consumed in producing the resources used in wastewater from the
analysis. It is unclear whether these are reasonable assumptions.
Karrmän, 1997, ”Analysis of wastewater systems, with respect to environmental impact
and the use of resources”. This thesis argues that urine separation systems are
favourable because of comparatively low use of natural resources and low degree of
eutrophication. An exergy analysis of alternative wastewater systems of Bergsjön (an
area within Göteborg) was performed. The study showed that the hypothetically
calculated exergy during operation would be lower for a separation system than for the
conventional alternative.
Carlander, Hoglund and Vinneras did a field experiment at Stockholm on the fertilising
value of source separated human urine. This four-year old project compares the
fertilising effect of human urine tot the effects of industrial fertiliser. Human urine is a
complete fertiliser with nutrient ratios N:P:K = 11:1:2.5. In 1998, crop yields from fields
fertilised with urine were identical to mineral fertiliser, both for fertilising before sowing
and during growth. (Sponsored by Stockholm Water Company and two housing
companies).
Ban and Lind, Göteborg University, are also doing research on struvite crystallisation
from human urine. The struvite will be tested as fertiliser under different conditions.
Petter D. Jenssen AN OVERVIEW OF SOURCE SEPARATION SYSTEMS
Department of Agricultural Engineering, Agricultural University of Norway
P. Jenssen et al.
A full-scale source separation system using vacuum toilets and grey water treatment in a
wetland
B. Vinnerås et al.
Environmental effects of urine separation in three different housing districts.
1.3
Commercial enterprises
Water Revival Systems (WRS)
WRS work with the design and construction of alternative wastewater and storm water
systems, specialising in urine separation systems. (Andersson and Ridderstolpe)
VERNA, Ekologi och Miljkonsult
VERNA provides consultancy services within the field of ecological wastewater
treatment with recycling technologies and is competent in urine- and black-water
separation.
2.
Novaquatis (EAWAG, Switzerland)
The Swiss Federal Institute for Environmental Science and Technology (EAWAG) is
located in Zurich. EAWAG's task as the national research centre for water pollution
control is to ensure that:
 Concepts and technologies pertaining to the use of natural waters are continuously
improved.
 Ecological, economical and social water interests are brought into line.
Within EAWAG, Novaquatis is a group of researchers concerned with fundamental
aspects of source separated sanitation. At the time of this report, no other group had
such a dedicated and thorough investigation into possibilities of source separation
technology. The research within Novaquatis integrates different fields of research to gain
knowledge of how to develop and implement new technology and avoid pitfalls.
EAWAG employs around ten people to take part in the Novaquatis project on a full time
basis. Some of many aspects of their research are:
1. Laboratory scale experimental work on treating separated urine and recovering
phosphorus, involving five people.
 P-removal/recycling by treating urine with membranes.
 Economical and ecological benefits (LCA) of P-recycling via urine.
In addition, they are building a network of different projects within Switzerland (pilot
projects, co-operation with soil and agriculture research groups).
2. Evaluation of consumer attitudes through discussion sessions with laymen and an online educational computer programme.
(http://www.novaquatis.eawag.ch/nomix_10/nomix.html)
3. Comprehensive evaluation of urine technology, including modelling of two scenarios
(urban - Winterthur and rural - Baden) where the ultimate question is: ”Does urine
separation technology constitute an overall improvement on current technology?”
4. Potential risks related to micro-pollutants (endocrine disrupters) in urine used as
fertiliser are being assessed.
5. Novaquatis assumes that all separately collected urine can be used as fertiliser. (This
will probably not be the case in the Netherlands.)
The Novaquatis internet address is: http/www.novaquatis.eawag.ch
3.
Otterwasser (Flintenbreite Eco-village, Lubeck, Germany)
R. Otterpohl (University Harburg Hamburg and Otterwasser) is developing more
sustainable water treatment techniques. One of these developments is an ecological
village (Flintenbreite) that was recently completed at Lubeck. The basic sanitation
concept at Flintenbreite involves:
 vacuum toilets collect faeces and urine
 bio-gas is produced on site and used as fuel
 nutrients from the bio-gas plant is collected and used as fertiliser in agriculture
Apart from R.Otterpohl, three other people at the University Harburg-Hamburg currently
work on concepts regarding “yellow water”, which might include aspects of phosphate
recovery.
Internet addresses are:
 R. Otterpohl’s company dealing with alternative sanitation:
http://www.otterwasser.de
 Eco-village Flintenbreite: http://www.flintenbreite.de/de/wasser2.html#was4
 Rural source separated sanitation at Lambertsmuhle:
http://www.otterwasser.de/homee.htm
4.
Austria
A new housing project in the city of Linz, called "solar city”, is underway in Austria. The
new housing estate will collect urine separately and constructed wetlands for treatment
of the "rest" of the wastewater (incl. the black water). There is also a market study on
how to introduce customers to separation toilets (maybe similar to Novaquatis’s
evaluation of consumer attitude). It is not yet sure if phosphate will be recovered from
the urine, or just used as fertiliser.
5.
Discussion
In most of the European projects, the assumption is made that urine can be used as
fertiliser (either directly, or in a treated form). One should note the following two
important restrictions:
1. Plants do not grow throughout the year, while people excrete urine every day. If urine
is returned to agricultural fields continually, groundwater and eventually surface water
will be contaminated.
2. The risks involved due to micro-pollutants in urine (hormones, pharmaceuticals) are
not yet completely understood.
Phosphate recovery could however make society more sustainable. One should
therefore also consider possibilities of recovering phosphate for use as a secondary raw
material. Raw materials such as coal, oil or phosphate rock are not renewable. The only
continual energy source is the sun. Even our renewable resources are naturally renewed
by solar power. Therefore the ultimate indicator of our level of sustainability is the way in
which we use energy.
Energy is contained in all chemical compounds as a potential to react with other
compounds, until a zero state is reached. This energy is called exergy or available work.
In this research the total exergy consumption of two alternative systems for reclaiming
phosphorus are determined.
 The first alternative is the conventional sewer/wastewater treatment system.
Sewerage is discharged to treatment plants where some of the “waste” compounds
are taken up in sludge (C, P and N) or released in the air (N2 and CO2), while the rest
is reclaimed by ion exchange and filtering.
 The second alternative is a system where urine is collected, transported and treated
separately. When urine is mixed with sewage, minerals are diluted and some of the
chemical exergy destructed. The separated urine can be used to form struvite
crystals. A portion of the urine is assumed to go to the wastewater treatment works
with other wastewater (wash water, rain water, faeces).
Two alternatives are illustrated in the figure below:
Chemical exergy flow of minerals (P) in wastewater
Food
Agriculture
Industry
Mining
(P)
Reclaiming
phosphorus
s
Excretion
Conventional
sewers
Source
separation
Wastewater
treatment
Wastewater
treatment
Reclaiming
phosphorus
Effluent
From the evaluation, it should be clear whether:
1) Separate collection and treatment of waste (water) products is a more sustainable
technique to reclaim minerals (such as phosphorus) than conventional sewers where
the minerals are reclaimed from lower concentrations?
2) Minerals reclaimed in either way reduce the current exergy loss of minerals that are
lost instead of reclaimed?
However, manure and urine from agriculture contains much more nutrients than human
urine (human urine in the Netherlands contains little more than 10% of the nutrients
when compared with live stock). Furthermore, manure and animal urine is locally
available and in a concentrated form.
6.
Conclusion
Many projects are initiated with the aim of improving sustainability in society. While this
is a worthwhile motive, it is unfortunate that many of these projects are often based on
trendy opinions. Technical, economic and social implications and health risks are often
neglected. However, experimental projects can still be of great value and our knowledge
of systems and alternatives may be increased by the “lessons learned”.
Only only a few groups, such as Novaquatis adopt pro-active holistic approaches. The
fundamental issues involved in these research programmes include health and safety,
wastewater treatment, mineral recovery, environmental benefits and consumer
perceptions.
Does the introduction of urine separation constitute an overall improvement in the water
system and society? This question not only concerns the possibilities of recycling
minerals (such as phosphate). It might be advantageous to collect and treat urine when
the closed cycles of minerals, water, health and environment are considered
simultaneously.
Urine separation could simplify wastewater treatment and reduce operational costs.
Although it can contribute only a small percentage, separated urine can still assist in
reclaiming minerals and protect finite natural resources. Thermphos can theoretically
recycle all the phosphates in municipal wastewater for non-fertilising phosphorus. There
may also be positive side effects such as improved surface water quality, reduction in
micro-pollutants and reduced effects of combined sewer overflows.
References:
Hanæus, Hellström, Johansson, 1997, A study of a urine separation system in an
ecological village in northern Sweden, Water Science and Technology, Vol 35 # 9
Jönsson, Stenström, Svensson and Sundin, 1997, Source separated urine-nutrient and
heavy metal content, water saving and faecal contamination, Water Science and
Technology, Vol 35 # 9
Jönsson, Dalemo, Sonneson and Vinnerås, 1998, Modelling the sewage system evaluating urien separation as a complementary function to the conventional sewage
system, paper presented at the Systems engineering models for waste management,
International workshop in Göteborg, Sweden.
Hellström and Kärrman, 1997, Exergy analysis and nutrient flows of various sewerage
systems, Water Science and Technology, Vol 35 # 9
Hellström, 1998, Nutrient management in sewerage systems: investigations of
components and exergy analysis, Doctoral Thesis, Lulea University of Technology
Karrmän, 1997, Analysis of waste water systems, with respect to envirenmental impact
and the use of resources, Doctoral Thesis, Chalmers University of Technology
Carlander, Hoglund and Vinnerås, Field experiment at Stockholm on the fertilising value
of source separated human urine, Conference report,
http://www.iees.ch/EcoEng991/EcoEng_A.html
Lind, Ban and Byden, Nutrient recovery from human urine by struvite crystalisation with
ammonia adsoprion on zeolite and wollastonite, Bioresource Technology 73 (2000)
Jenssen, An overview of source separation systems. Department of Agricultural
Engineering, Agricultural University of Norway,
http://www.nlh.no/Institutt/Departments.htm
Jenssen, A full-scale source separation system using vacum toilets and greywater
treatment in a wetland, Agricultural University of Norway,
http://www.nlh.no/Institutt/Departments.htm
Vinnerås, Environmental effects of urine separatin in three different housing districts.
Agricultural University of Norway, http://www.nlh.no/Institutt/Departments.htm
Andersson
and
Ridderstolpe,
http://swedenviro.com/wrs_en.html
Water
Revival
Systems
VERNA, Ekologi och Miljkonsult, http://swedenviro.com/ver_en.html
(WRS),