Planted Filter: A Modern Reed-bed System – TLS #58

This article originally appeared in TLS #58.

by Rene Kilian – Denmark

Save money on your black and grey water while protecting the environment!

Reeds and iris clean the wastewater in the planted filter.

All properties without sewage facilities in rural areas of Europe must meet minimum standards for wastewater treatment. It can be expensive joining on to the main sewage lines. A planted filter’ – a modern kind of reed-bed system with vertical waterflow – has low operating costs and is an inexpensive alternative.

Approximately 30 of these filters have been built in Denmark. The systems are planted with wetland plants, and occupy around 16m2 per dwelling.

The system complies with the latest Danish standards, which are stricter than the European standard.

Along with this, environmental impact is reduced and the homeowner can save money on sewage connection and payments.  The investment can be paid for through savings in less than five years, when compared to a standard sewage connection. Here is an example.

Reuse of treated wastewater Søren Raffnsøe built his own straw-bale house, went about it in a way that was as environmentally and economically friendly as possible. The way that water comes in and out of the house has been considered in a holistic manner, and is the first of its kind in Denmark.

The house has its own planted filter to treat wastewater. The system is only 8m2 because the house has a composting toilet.

The planted filter is a biological-cleaning system. The system, designed by René Kilian, is an effective alternative to a sewage connection. The system can even be integrated into a garden where it could resemble a garden bed growing with thatching reeds, iris and bullrushes.

Figure 1. A recycling system with the planted filter where water is reused in the washing machine and garden. 1. Sedimentation Sedimentation tank for grey wastewater only. The source of the water may vary depending on local codes or regulations but might include water from bath, washing machine and kitchen. 2. Pump well with a level controlled pump. 3. Reed bed system or constructed wetland. 4. Tank for treated wastewater and treated rainwater. 5. “Green” pipe for reuse water to washing machine and garden. 6. Water vitalizer in drinking water pipe. 7. Fine filter for treatment of rainwater. 8. Untreated rainwater toward sand catcher and infiltration unit. 9. “Black”’wastewater from toilet to compost container. 10. Urine from toilet to urine container Design by Kilian Water Ltd., Denmark

The recycled water becomes so clean that you can reuse it to flush the toilet, wash clothes and water the garden. As compost toilets don’t use water, Søren uses the water only in his washing machine and garden. See Figure 1.

Along with this, he saves 50 percent in his usage of drinking-quality water. To collect the excess recycled water, he has made a little pond in the garden, where there is an extra cleaning process that created a habitat for plants and animals. The drinking water itself is also special. He has installed a ’vitalizer’ in his drinking water pipes. This revitalizes the water so it attains the same quality as spring water.

Payback in less than five years

A planted filter of 16m2 suitable for a normal household, will cost around 60,000 Danish kroner/$11,083.80 USD. Connection to public sewage costs one household around 40,000 kroner/$7,389.21 USD. The investment can be paid back in less than five years, as you can save on annual wastewater bill payments. Ongoing costs for a planted filter are 0 kroner /m3; there is just a government tax of 1.60 kroner /m3. Costs for sewage are approximately 35 kroner /m3. This means a dífference of nearly 33.50 kroner / m3. With an average consumption of 170m3 per year, a household would save around 5,700 kroner/$1,052.96 USD per year, or 140,000 kroner/$25,862.20 USD after 25 years.

The planted filter at 8m2 in front of the newly built straw-bale house.

If you chose a reuse system in addition to this, and saved 50 percent on water consumption, you save 7,000 kroner/$1,293.11 USD per year. After 25 years, you will have saved 175,000 kroner /$32,327.80 USD. With the correct wastewater solution, you can really save money and protect the environment.