Arne Backlund (Corresponding author) A & B Backlund ApS, Ordrupvej 101,DK-2920 Charlottenlund, Denmark Tel. +45 39633364 Fax +45 39636455 E-mail backlund@backlund.dk Annette Holtze Storstrøm County, Technology & Environment, Parkvej 37, DK-4800 Nykøbing F. ABSTRACT Storstrøm County and A & B Backlund ApS have co-operated on a project to collect experience and to examine Denmark's earliest evapo-transpiration bed with no outlet, situated in Storstrøm County. Results from the project Danish EPA M226-0025 “EXPERIENCE AND EXAMINATIONS FROM AN EVAPOTRANSPIRATION BED WITHOUT DISCHARGE AT TAPPERNØJE” are presented in this paper. The bed has worked very stably since 1992. The water balance has been calculated to estimate the evapo-transpiration of the bed. The content of nutrients in the wastewater, and nutrients, heavy metals and organic compounds in the soil have been analysed. Steam production of the willows has been estimated. A & B Backlund ApS is engaged in further development of the systems. Key words: #Willowevapotranspirationbeds, #willowvegetationfilter, #wastewatertreatment, #ecologicalengineering, #ecologicalsanitation

1. WILLOW EVAPO-TRANSPIRATION BEDS
WITHOUT DISCHARGE - FOR HANDLING
OF HOUSEHOLD WASTEWATER
Figure 1 The evapotranspiration willow bed at “Marjatta” Storstrøm county
Arne Backlund (Corresponding author)
A & B Backlund ApS, Ordrupvej 101,DK-2920 Charlottenlund, Denmark
Tel. +45 39633364 Fax +45 39636455 E-mail backlund@backlund.dk
Annette Holtze
Storstrøm County, Technology & Environment, Parkvej 37, DK-4800
Nykøbing F.
ABSTRACT
Storstrøm County and A & B Backlund ApS have co-operated on a project to collect
experience and to examine Denmark's earliest evapo-transpiration bed with no outlet, situated
in Storstrøm County. Results from the project Danish EPA M226-0025 “EXPERIENCE AND
EXAMINATIONS FROM AN EVAPOTRANSPIRATION BED WITHOUT DISCHARGE
AT TAPPERNØJE” are presented in this paper. The bed has worked very stably since 1992.
The water balance has been calculated to estimate the evapo-transpiration of the bed. The
content of nutrients in the wastewater, and nutrients, heavy metals and organic compounds in
the soil have been analysed. Steam production of the willows has been estimated. A & B
Backlund ApS is engaged in further development of the systems.
Key words: Willow evapotranspiration beds, willow vegetation filter, wastewater treatment,
ecological engineering, ecological sanitation

2. EXPERIENCE AND ANALYSES FROM DENMARK'S EARLIEST
EVAPOTRANSPIRATION BED WITH NO DISCHARGE
In Denmark there are about 50-100 willow evapotranspiration beds, primarily used in
individual houses. The "Pilehuset", a shared living complex, established the earliest one in
1992 as part of ”Marjatta”, an establishment for disabled persons, situated in Tappernøje in
Storstrøm County. Since 1992 the willow bed has received and evapo-transpired
approximately 1 m3
of wastewater per day from eleven people, exclusive of rainwater falling
on the bed (1).
THE CONSTRUCTION OF THE WILLOW EVAPO-TRANSPIRATION BED
Figure 2 The construction
In principle, the bed is like a container planted with willows at the top, and with a waterproof
geo-membrane, 0.7 mm LDPE at the bottom and along the sides.
PilerenseanlægWillow bed
tictank
EfterklaringsbrøndFinal sedimentation Sand GeomembranGeomembrabebraneraneanenee Fibertexretex
Inlet from septict.
16/32 singels 20 cm
Willows
Raw soil 70 cm
Humus 30 cm

3. Figure 3 Laying down the LDPE
It receives wastewater from a sedimentation tank by gravity to spread at the bottom of the
bed through a Ø 160 mm pipe with Ø 100 mm holes at intervals of 5 m. The surface is 707 m2
(64 m2
/p) and the depth 120 – 135 cm. The layers above the plastic membrane consist of 10
cm of sand, 10 cm of gravel, 70 – 85 cm of raw earth by both the inlet well and the outlet
well, with 30 cm of humus at the top. A fibre textile separates the raw soil and the distributing
layer in order to prevent roots from entering the pipe.
Figure 4 Gravel and fibre textile
The cubic content has been calculated to be 690 m3
above the fibre textile and 150 m3
under
it. The density of planted willows was about 3 - 4 plants/m2
(1).
EXPERIENCE AND EXAMINATIONS
*The construction and establishment of the bed as well as the experience concerning working
stability and operation demands have been described.
*The mass balance for water has been worked out.
*The content of nutrients in the wastewater has been measured.
*The contents of nutrients, heavy metals and organic compounds in the soil have been
measured.
*A budget for nutrients has been drawn up.
*The annual growth of the willows has been estimated.
*The growth of different clones has been discussed (1).
RESULTS
*The working stability of the bed is excellent.
*The evapo-transpiration of the bed has been very good, 1,310 – 1,370 mm/year.
*Up to 60 percent of the stored and evapo-transpired water was rainwater.
*There are no indications of the heavy metals being a limiting factor for the future handling of
the soil.
*Salt can be a limiting factor for growth and evapo-transpiration, but it can be removed
during summer time at low water levels.

4. * The application of diverting toilets can reduce the amount of sodium chloride and the
surplus of nutrients led to the bed (1).
FUTURE R & D
*The application of bred, optimalised-growing willow clones with an even larger evapo-
transpiration potential in order to minimise the surface and costs of the bed.
*Experiments with discharge of rainwater from the surface before contact with the
wastewater, in order to minimise the volume, the surface and the costs of the bed.
*Experiments with raising the porous volume in the beds from approximately 35 % to 80 %.
*Experiments with the growth and evapo-transpiration from willows growing under the above
conditions.
*Estimation of critical salt levels.
NEW TEST PROJECTS
Two beds have been established in 2001 according to the principles of the rainwater
discharge and of clones bred. One is established in Denmark, and one in Germany.
REFERENCES
1. Holtze, A., Backlund, A. 2001: Erfaringer fra og undersøgelser af pilerenseanlæg i
Tappernøje. Storstrøms Amt. ISBN 87-7726-328-6
Holtze,A., Backlund,A. 2001: Erfaringer og undersøgelser af pilerenseanlæg i Tappernøje.
Økologisk byfornyelse og spildevandsrensning 17, 2001. Miljøstyrelsen.
www.mst.dk/udgiv/Publikationer/2001/87-7944-756-2/html