What is it?

Filter marshes have been used for many years to purify wastewater. In recent decades, German researchers drew inspiration from these wetlands to develop artificial filter marsh technology. These built ecosystems now treat a wide range of wastewater, including municipal, industrial and agricultural effluents.

What is it used for?

Filter marshes provide an effective and environmentally friendly alternative to septic tanks, leaching fields and sewer systems:

  • As self-sufficient systems, they require little maintenance.
  • Their installation and operation cost less than traditional methods.
  • They do not require any chemicals and little or no energy from external sources.
  • They provide a habitat for wildlife and beautify the landscape.

The vast majority of artificial filter marshes treat domestic wastewater, but they can also purify effluent from fish farming, paper mills, dairy farms, landfills and mining operations.

How is it made?

A typical filter marsh consists of a basin with or without a substrate (soil or gravel), a wastewater intake system and a purified water output system. Plants (floating or rooted) play an essential role. Their roots, and particularly the microorganisms associated with them, promote the breakdown of numerous pollutants.

There are several types of filter marshes, which are suited to specific uses and regions. Hybrid filter marshes combine many of their best features, allowing users to benefit from the many purification mechanisms.

Until recently, the common reed (phragmites australis) was the star plant in filter marshes, but it is no longer allowed in Quebec because of its invasive nature. Fortunately, researchers have identified other extremely effective plants, including cattails

In Quebec

For 20 years, the Biosphère on Montreal’s Île Sainte-Hélène has treated its wastewater by means of the plants and microorganisms found in the outdoor basins where the water collects.

Photo: Vista Photo

In the world

Le Baluchon inn, in Saint-Paulin, has treated all its wastewater with filter marshes since 2007. A total of 135 m3 of water per day flows into three large basins covered with plants.

Photo : Jacques Brisson

The village of Roussillon, in France, uses filter marshes to treat the wastewater produced by its residents, who number 300 in the winter and up to 1,320 in the summer tourist period. Its marshes were designed to handle the large seasonal variations.

Photos: Jacques Brisson