
Constructed wetlands and phytoremediation: using plants (plus the microbes around their roots) to strip nutrients, organic matter, and some pollutants out of wastewater as it flows through gravel, soil, or shallow ponds.
Can you believe plants can turn toilet wastewater into clean, usable water? It sounds crazy, but it’s 100% possible — no chemicals just nature!
80% of the world’s wastewater goes untreated and most people don’t even know this, but it’s a serious problem. The good news is that the solution is simple and scalable.
Here’s how it works:
1 Plants are placed in a special system filled with gravel. They grow and prepare to clean the water.
2 The magic happens under the surface – as the water flows, plant roots and bacteria remove waste and harmful substances.
3 Clean water flows out! Safe for irrigation, flushing toilets, or returning to nature.
Imagine if every building treated its own wastewater. We could save millions of litres and restore biodiversity at the same time.
Cattails are a classic example, but there are many other species used in these systems to clean wastewater. Here are some of the main groups and examples:
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Reeds and rushes
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Common reed (Phragmites australis). Widely used in horizontal and vertical flow reed beds to treat domestic wastewater and sewage; roots provide huge surface area for bacteria that break down pollutants.aquatiris+1
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Bulrush / soft rush (e.g. Scirpus spp., Juncus effusus). Good at removing nutrients like nitrogen and phosphorus and stabilising the substrate.kellogggarden+1
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Iris and similar ornamentals
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Yellow flag iris (Iris pseudacorus) and related species. Used because they tolerate nutrient-rich water, help remove pollutants, and look attractive in “garden wetlands.”aquatiris+1
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Floating aquatic plants
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Duckweed (Lemna spp.) and azolla (Azolla spp.). Research shows they are particularly effective at taking up nitrogen and phosphorus from wastewater.phys+1
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Water hyacinth (Eichhornia crassipes). Very efficient at absorbing nutrients and some heavy metals, used in lagoon systems—but invasive in many regions, so must be controlled.oas+1
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Other wetland and marginal plants
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Carex sedges (Carex spp.). Often used alongside reeds and rushes in constructed wetlands.aquatiris
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Water mint (Mentha aquatica) and similar species, which can help reduce bacterial contamination in small-scale systems.kellogggarden
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In practice, designers usually combine several of these plants in layers (gravel beds, shallow pools, planted margins) to target different pollutants and make the system more robust.








