The ordinary passer-by in the Sint-Pieterstraat in Ledegem might notice at a good moment; At the height of a piece of West Flemish farmland, opposite an elongated ribbon of houses, a seventy meter long box with flowers has been constructed in a canal. Wild catnip, blue geraniums; plants with fleshy roots, ending in fine hairs, which branch up to a meter in the soil. And in doing so, they rid the inhabitants of a problem that had taken on more and more pungent forms. It stunk there. To poo.
People in several places in Flanders are bothered by this ‘odor nuisance’, as the mayor of Ledegem Bart Dochy calls it. Almost half a million homes are not connected to the sewer system – in the Netherlands there are still about eight thousand. This is due to the famous Flemish ribbon development. That makes sewage expensive.
In municipalities such as Ledegem, West Flanders, wastewater often ended up in large tanks in gardens. And fourteen houses on Sint-Pieterstraat discharged their wastewater in a medieval canal.
Ledegem would get a pressure sewer system. Wastewater is first collected in tanks and then pressed through high-pressure pipes to the treatment plant. “But actually I didn’t believe in it,” says the mayor. Construction would take a long time. “And because of the drought I thought it would be better to keep water in place. Knowing that we have to meet European water guidelines by 2027, I was very happy when I met Wouter Igodt two years ago.”
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Igodt, a 43-year-old landscape gardener from the area, had already been discussing a system for purifying water with plants for twelve years. He did this in ponds that he built in people’s homes with reed, but it had to be done smarter and more efficiently.
Moving water
In 2016, Igodt was allowed to participate in a Dutch-Flemish collaboration to develop sustainable waste water facilities in the outlying areas. And that is necessary, now that the European directive is approaching. Igodt: “You would prefer to keep waste water on site, at a better quality. This benefits the soil and biodiversity. All that water doesn’t have to be moved all the time anyway. That just costs energy.” So Igodt tinkered with a helophyte filter that can be installed on site. Man allows nature to solve its problems.
Two years ago he installed a helophyte filter for a restaurant in Kuurne. The Flemish Environment Agency VMM, the regulator for air, water and soil, was skeptical. “It’s easy with sewers; pipes go into the ground and you don’t see them anymore,” says Igodt. “But that changes when an installation comes above the ground. At the VMM they mainly want to know: who is going to manage and maintain that?”
It is the bacteria that purify the water
Wouter Igodt landscape gardener
Nevertheless, one and a half years ago, Dochy teamed up with Igodt and his company to construct a helophyte filter for the Sint-Pieterstraat. The municipality paid a part itself, and used money from a pot from the Flemish government to combat drought.
In Ledegem, especially the stench, something had to be done quickly. With the construction of traditional pressure sewers, that would have to wait until 2032. Igodt’s system was there in three weeks. Dochy also saw financial opportunities. “Flanders had already allocated 1.8 million euros for pressure sewerage in the Sint-Pieterstraat,” he says. “I want to use that money for Wouter’s filter, which costs less than a third in total; 540,000 euros.”
Anyone who takes a look at the Sint-Pieterstraat in Ledegem has no idea of the technology that is hidden in the gigantic planter. The layman sees only flowers, bees and butterflies. But next to the driveway to a strip of land, under a manhole cover, lies a system that costs more than a sports car.
Sticky household fats
The waste water from the homes is collected in a buried pre-settling tank. Solid particles sink and everything that remains liquid overflows into a pump sump where sensors measure values such as oxygen content and temperature before two pumps bring the water to the planter. That’s where the magic happens, says Igodt. “In cross-section you first see plants from top to bottom. Then a layer of lava rock from Germany. This is a porous rock to which household fats stick. Below that you have a layer of 70 centimeters with our substrate. This is a material that we already researched eight years ago, and which enables plants to take root very well. It ensures optimal cooperation between roots and bacteria, in the top layer with (aerobic) and the bottom layer without oxygen (anaerobic). It is the bacteria that purify the water.”
Seventy yards away, on the other side of the filter, a faint trickle of crystal-clear water flows out, cleared of feces and other noxious substances. That water is also measured just before the exit of the filter. Igodt publishes the results in real time on a website. In this way he hopes to convince the VMM and other Flemish municipalities of his system. After a broadcast on Flemish TV he already received 75 applications.
Mayor Bart Dochy has allowed him to continue building. A little further on will be two large planters with helophyte filters that will ensure that another sixteen homes and a café no longer cause odor nuisance. Dochy is convinced that the Flemish authorities will come up with money, because Igodt’s solution is faster and cheaper than traditional sewerage. And also contributes to the solution to a current problem: the ongoing drought.