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Collection, storage, and utilisation of urine from Museumsgården on the island of Møn

Summary and conclusions

In the autumn of 1998, Storstrøm County initiated the project "Collection, storage and utilisation of urine from Møns Museumsgård" (the museum farmstead of Møn). A summary of the project report is presented below.

In order to clarify how urine can be recycled in Denmark, Storstrøm County initiated the project "Collection, storage and utilisation of urine from Møns Museumsgård Møns Museumsgård". The project was funded by the Municipality of Møn, and by the Danish Environmental Protection Agency through the "Action Plan for the Development of Ecologic Renewal of Towns and Wastewater Treatment". The initiators of the project were Møn Museum/"Museumsgården", Den Grønne Guide på Møn (the Green Guide of Møn), A & B Backlund ApS (a private limited company) and Storstrøm County. Together they developed and planned the project.

The wastewater from "Museumsgården" contains a high quantity of urine and a small quantity of unidentified substances, and this makes the separation of urine by way of source-diverting toilets and the utilization of nutrients reasonable. Contrary to a private house, there are many different users of the toilets at a museum. This fact makes it possible to test a segregating wastewater system under somewhat difficult circumstances.

One of the purposes of the project is to collect experience in the installation and use of a source-diverting toilet system, including a waterless urinal, at the "Museumsgården" and to compare this with experience from Sweden.

Another purpose is to examine the constituents of the urine, including whether the contents of nutrients, heavy metals, micro organisms, and xenobiotic organic substances will change during storage. Moreover, the urine collected was compared with other urine mixtures and fertilizers on the basis of these parameters.

Storstrøm County has not carried out its own test programme, as the Danish Environmental Protection Agency initiated the project "Assessment of the possibilities and limitations of the recycling of nutrients from town and country households " (Dalsgaard & Taarnow, 2001).

The toilet system at the "Museumsgården" was established in April 1999. Experience from the installation and operation was collected during the opening seasons 1999 and 2000, and partly during 2001.

The examinations include interviews concerning the installation and operation of the source-diverting toilet system. Apart from this, analytical results were prepared on the basis of the coordinated test programme of the Environmental Protection Agency concerning the content of nutrients in the urine collected, as well as heavy metals, micro organisms and xenobiotic organic substances.

The "Museumsgården" is described on the basis of the number of visitors and other relevant characteristics important to the quantity and quality of accumulated wastewater.

In this chapter, concentrated urine as a fertilizer is characterized. Compared to the content of other effluent flows from a household, human urine is contains the main part of the nutrients. Normally, human urine totals 1-1.5% of the household wastewater, but it contributes approx. 80% of the nitrogen, 55% of the phosphor, and 44% of the potassium in wastewater.

Although human urine contains most of the nutrients in household wastewater, urine contains only a small proportion of the total content of heavy metals. Heavy metals from human beings are mainly secreted through faeces.

Health risks related to the application of urine is generally not looked upon as connected to the urine itself, but to the mixture of urine and faeces, which has a high content of micro organisms. If urine is to be utilized as a fertilizer, it is crucial that the source-diverting sanitary systems are established in a way that cross contamination (the mixture of urine and faecal material) is kept at a minimum. Moreover, to secure a good concentration of ammonium and a high pH factor the supply of flush water must be limited; this is of great importance to the reduction of micro organisms during storage.

Today the "Museumsgården" is run as part of the Møn Museum. The "Museumsgården" is open from May 2^nd until October 31^st. On average, approx. 4,500 people visit the museum every year, of which 1/3 are children. The production of wastewater is relatively low. Prior to the project start, the annual water consumption was approx. 150 m³, of which 30 m³ are estimated to have been used outdoors. This consumption corresponds to the consumption of an ordinary household. The composition of the wastewater differs from ordinary household wastewater, as the majority comes from flushing toilets and washbasins.

As part of the project, the old porcelain bowls with flushing tanks placed under the ceiling have been replaced. The exact amount of flushing water for the old toilets is unknown, but it is estimated to be about 9 litres (approx. 2 gallons).

In the gentlemen's lavatory there has been a stand urinal with a stainless steel drain and with controlled, automatic flush from two cisterns. The urinal has had an automatic flush approx. every 15-20 minutes, using an unknown quantity of water.

With the exception of the sedimentation tank, the existing toilet system has been replaced by a source-diverting system. Four source-diverting, double-flush, porcelain closets as well as a waterless, gel-coated, fibreglass wall urinal have been established. The surface of the urinal makes the urine glance off. Inside the urinal there is a siphon, which constitutes an odour seal in combination with a sealing liquid.

The segregated urine/flush water of the urinal bowl is led into storage tanks made of polyethylene. The remaining wastewater is still led into the sedimentation tank. The cycle of the application of the tanks was planned to be 6 months' collection in tank 1, and after that 6 months' storage during the filling of tank 2. The two tanks are each emptied once a year at 6-month intervals. The capacity of the tanks, however, has turned out to be larger, i.e. a possible storage period of more than 12 months.

Systems for treating wastewater fall under the Environmental Protection Act and the Building Act. This chapter contains a short comment on the legislation relevant to the establishment of a source-diverting wastewater system. When the permission is given for the establishment of a wastewater system including the collection of human waste products in a collection tank, it must also be ensured that emptying, transportation and final disposal take place in a proper way.

No general test and approval conditions are laid down for urine-diverting toilets. Therefore, each installation must be granted separate approval. This also applied to the urinal at the time of establishment, but later a VA approval has been granted. The pipe installations of a wastewater system must be made in accordance with the Discharge Code DS 432.

Wastewater, including human waste products with agricultural value, may be used for agricultural purposes according to the Sludge Regulations (regulation no 49 of January 20^th 2000 on the application of waste products for agricultural purposes). The county may give permission to make use of these products. The applications of urine and other human waste products depend on the way they have been treated. Basically, they are comparable with night soil; but in case of further treatment of the products to the effect that they no longer may be considered as night soil, they can be used in farming and private gardening (according to the guidelines from the Environmental Protection Agency, no 5/1999 on the regulations regarding wastewater permits etc.). The treated end product may be compared with residual sludge regarding restrictions on use laid down for sanitary reasons (cf. appendix 3 of the Sludge Regulation).

The experience from the establishment of the source diverting wastewater system at the "Museumsgården", as well as the experience from the operation during the seasons of 1999, 2000 and part of 2001 is summarized in this chapter. No problems arose in connection with the establishment of the system or with adjusting the flush. Due to an error, the storage tanks for urine were not properly fixed when they were buried underground. The light tanks rose because of the water pressure, and they later had to be fastened. Moreover, at first the bracket connecting the shanks and the tanks was not properly sealed. This meant initial problems with water leaking in from the surroundings.

The overall experience has been positive – maybe even surprisingly positive, if the fact that there are many, different toilet users at the "Museumsgården" is taken into account.

No problems with the flush mechanism of the toilets have been reported, and no odour problems from the toilets have been observed. The staff have noticed no faeces in the small urine bowl or at the section between the urine bowl and the faeces bowl. This indicates that no major cross contamination has taken place.

The staff have observed that the toilets demand a little more cleaning than traditional toilets. The short flush has not been able to keep the urine bowl completely clean, using a flush of about 2 decilitres. Approx. every 3 weeks the staff have poured a mixture of water and acetic acid into the water seal to prevent it from choking, among other things because of the crystallization and deposit of salt.

To use the toilets correctly, sufficient instructions for use are necessary. This precondition has apparently been met, as printed instructions on the lavatory doors and walls tell how to use the toilets.

After 3 seasons, the inside surface of the urinal is intact and smooth, so that the urine still glances off. There are no visible remains of urine in the bowl. The surface has not been vandalized, and it has so far not been necessary to polish the surface with car-polish, as recommended by the manufacturer. Nor have there been any odour problems. Even though the manufacturer recommends replacement after 5,000 – 7,000 visits, or at least once a year, there has been no need for the siphon to be replaced since it was fitted in 1999.

No inquiry has been made into the visitors' experience from the toilet system of the "Museumsgården". Interviews with the staff and the impression of the Green Guide's conversations with visitors imply that the visitors have generally approved of the new system and have expressed their satisfaction with the way it works. Even during the busy annual fair day, with up to 600 visitors, the system functioned impeccably, without odour problems or other problems.

A few have expressed that they were not comfortable putting the toilet paper into a bin in connection with a "quick visit". In this case visitors can abstain from following the instructions and put the paper into the large bowl and activate "full flush" instead.

The special exhibition about the subject along with the establishment of the new system has proved a good idea. The exhibition has given rise to many formal conversations about toilet systems in general. It seems that the exhibition has reduced the problem of trying something so completely different.

During the season of 1999 (from May 2^nd – October 31^st) approx. 1,830 litres (about 40 gallons) of urine mixed with water was collected in tank 1. The number of visitors during the season was 4,320. During the period from November 1^st 1999 to September 1^st 2001, 2,640 litre of urine mixture was collected in tank 2; the number of visitors was 6,856. The analyses of the coordinating test programme have been carried out for the urine mixture in tank 1. Chapter 8 deals with the results of the analyses of the constituents of the urine mixture stored. The results are compared to the analyses of other fertilizers.

The urine mixture from the "Museumsgården" has a percentage of dry solid matter of 0.3384, and contains approx. 3,300 g nitrogen (N), approx. 135 g phosphorus (P) and approx. 1,250 g potassium (K). Potassium is normally the best indicator of the concentration of the urine mixture. If the ratio between urine and flush water is based on the concentration of potassium, there is a urine content of 35%, corresponding to a ratio of 641 kg of urine to 1,189 kg of flush water. The collected urine mixtures are not only diluted because of the flush water: it is not possible to retain the total quantity of urine in the source-diverting toilets. The percentage of collected urine through the source-diverting toilets on Møn is also unknown. Examinations of toilets in Swedish apartments have proved a collection percentage from 50 to 80 %(Jönsson et al., 200, Vinnerås, 2001). Further development of the toilets will probably result in the collection of a more concentrated fertilizer.

The test results from Møn have been compared to test results from urine tanks of similar source-diverting toilets in the rented dwellings at "Hyldespjældet" in Albertslund near Copenhagen, and from the Svanholm Estate. Moreover, they have been compared to a test from ten allotment garden houses equipped with source-diverting dry closets with little or no manual flushing. All the projects belong to theme 3 of the Action Plan. The analyses show that urine mixtures have a considerable content of nitrogen, and that the content of phosphorus is low – lower than in concentrated urine. The lowest content of phosphorus was demonstrated in the urine mixture from Møn.

The nutrient content of the urine mixture from the "Museumsgården" is compared to the content in concentrated urine and to residual sludge, compost, and liquid manure, used as fertilizers. The content of nutrients (N, P, K) in the urine mixture is "thin" compared to the other fertilizers, but the low concentration of dry solid matter makes the urine mixture most suitable for spreading through sprinkling systems.

As part of the coordinated test result programme, the content of xenobiotic heavy metals and organic substances in the urine has been tested. The results have been compared to the content in the urine mixtures from the other diverting systems, including concentrated urine, and to results from similar analyses of other fertilizers. The results prove that the content of heavy metals and xenobiotic substances in urine mixtures is low. Thus, on the basis of dry solid matter, the content in concentrated urine and in urine from the "Museumsgården" is down to thousandths of the marginal values which apply to the spreading of residual products allowed for agricultural purposes (according to regulation no. 49 of January 20^th 2000).

The analyses moreover show that the content of heavy metals in the urine mixture is considerably lower than in other fertilizers. The concentration of Cadmium (Cd) in the urine mixture, in relation to the dry solid matter from the "Museumsgården", constitutes only a couple of per cent of the concentrations found in liquid manure and only a couple of thousandths of the content in residual sludge and compost. The differences are more evident if the content is calculated in relation to the content of nitrogen and phosphorus, and is most evident for nitrogen.

The content of xenobiotic substances in the urine mixture, calculated on the basis of the content of nitrogen and phosphorus, is down to thousandths of the content in residual sludge and composted household waste. The content of PAH and NPE in liquid manure is at the same level as that in the urine mixture. This is not surprising, as the source of these substances is primarily the flush water.

The results of the microbiological analyses of the coordinated test programme were compared to the content of the urine mixtures in the other three projects under the theme. The number of Enterococci serves as an indicator of faecal pollution of the urine mixture. The quantity of Enterococci in the urine mixture from the "Museumsgården" had already been reduced to less than 10 per 100 ml after 2½ months. The quantity of Enterococci and Escherichia coli would typically fall to below the limit for detection after 3-4 months' storage of the urine mixture, with some individual modifications in the projects (Dalsgaard & Tarnov, 2001). The bacterial count of the urine mixtures, at 37º, also fell considerably during the first month of storage.

The disintegration rate of the bacteria depends on the pH and temperature conditions in the storage tanks. The pH should be min. 8.8, and the temperature 20^oC rather than 4^oC (Jönsson et al., 2000, Höglund, 2001). During the last part of the test period, the temperature of the storage tank rose, and the pH factors registered were not quite up to the mark. This may be due to the fact that the urine mixture has a relatively low concentration of urine.

The microbiological analyses show that no Salmonella or Camphylobactor have been found. After 2½ months' storage, the content of Enterococci in the urine mixture from the "Museumsgården" was less than 100/g. In this respect the urine mixture meets the current hygienic performance criteria, laid down in the sludge regulation (regulation no. 49 of January 20^th 2000 concerning waste generation for agricultural purposes). The treatment of the urine mixture, however, does not quite correspond to the definition of controlled sanitizing laid down in the regulation. These demands must be met before spreading.

Dalsgaard & Tarnov (2001) conclude that after 4 months' storage of separately stored urine mixture a considerable reduction in bacterial infectious matter is obtained. "Utilization of stored urine as a fertilizer seems to constitute an insignificant risk of bacteria-based gastrointestinal infection with animals and human beings in the handling of urine, and in the consumption of urine-fertilized crops".

The presence of the parasite Chryptosporidium parvum (Dalsgaard & Tarnow, 2001) was demonstrated, whereas the parasite Giardia duodenalis was not found in the urine mixture from the "Museumsgården". The Danish Environmental Protection Agency has, among other things for this reason, started an analysis of risks of the collected urine (Linda Bagge, personal information).

In this chapter, a number of examples and experience from installations of source-diverting toilet systems in various types of housing in Sweden is introduced in order to be able to compare with the Danish experience. The application of urine in Sweden, as well as the recommended regulations concerning the utilization given by the Smittskyddsinstitutet (epidemiological institute) in Stockholm and the Swedish Agricultural University, SLU), are discussed.

Here, some of the important questions related to the recycling of urine are discussed, i.e. the reliability and efficiency of the waste water systems in relation to the collection of urine, the concentration of nutrients in the urine mixture, as well as the problems concerning cross-contamination. An important subject is the quality of the nutrients collected in the urine mixture concerning both the content of nutrients, xenobiotic substances, and micro organisms.

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