What they did falls under phytoremediation — a process that uses plants to remove pollutants from soil, water, and air. A sustainable and cost-effective alternative to traditional remediation methods, phytoremediation was successfully tested in many locations and is being used at several sites connected to the Superfund program.
In the context of wastewater treatment, phytoremediation schemes can be used to remove pollutants and nutrients from wastewater, reducing the need for traditional energy-intensive and expensive treatment processes.
|Phytoremediation can be applied in situ, which means that the plants are grown directly in the contaminated soil or water, or ex situ, which means that the plants are grown in a separate container or bed and the contaminated soil or water is pumped through the system. |
The choice of approach depends on the specific contaminant, the site conditions, and the desired outcome.
4 Phytoremediation Schemes for Wastewater Treatment
Constructed wetlands (CWs) are engineered systems that use natural processes to treat wastewater. They consist of a shallow basin filled with gravel and sand, and a variety of wetland plants. Wastewater flows through the system, and the plants and microorganisms in the soil remove pollutants.
Floating Treatment Wetlands
Floating treatment wetlands (FTWs) or islands are small artificial platforms that allow aquatic emergent plants to grow in water that is typically too deep for them. The plants are grown on a floating mat that sits on the water’s surface.
The processes that make Floating Treatment Wetlands effective at cleaning fresh water. Source: IISD
Subsurface Flow Wetlands
Subsurface flow (SF) wetlands are similar to constructed wetlands, but the wastewater flows through a layer of gravel and sand beneath the surface. The plants and microorganisms in the soil remove pollutants, and the treated water is collected in a drainage layer beneath the gravel and sand.
The water flow path through a subsurface flow constructed wetland. Source: ResearchGate
Free Water Surface Wetlands
Free-water surface (FWS) wetlands are similar to constructed wetlands, but the water surface is exposed to the atmosphere and direct sunlight. Most natural wetlands are FWS systems, including bogs (primary vegetation mosses), swamps (primary vegetation trees), and marshes (primary vegetation grasses and emergent macrophytes.)
Plants for free-water surface flow constructed wetlands. Source SA’AT (2006
Moving Past Wetlands
Phytoremediation can be used to treat a wide range of contaminants, including heavy metals, organic pollutants, and radioactive materials. It is a cost-effective, environmentally friendly, and sustainable approach that takes advantage of the ability of plants to concentrate elements and compounds from the environment and metabolize various molecules in their tissues.
The various types of wetlands are just one way of applying it: some others include phytoremediation of Cd-contaminated farmland soil via various Sedum alfredii-oilseed rape cropping systems; bioremediation of Leachate-Contaminated soils with microorganisms; and more.