How Wetlands and Natural Systems Purify the Water We Depend On

Field report

Preventing water pollution in the first place would be best. But as we face mounting environmental challenges, natural purification systems can help us find a path forward.

Natural water purification is a fascinating area to explore if you are interested in ecology, wetlands, and habitat restoration. This is the process by which wetland plants, soil microbes, and natural filtration clean contaminated water, soil, or air. There is a wide range of natural processes that can be harnessed to purify the waterways we depend on.

We all know that human development often comes at a cost to the environment. Many rivers, lakes, and wetlands have been severely degraded by human activity — and polluted by industry, agriculture, and poor waste management. But the good news is that natural purification systems can be utilized to remove or reduce pollutants and restore waterways that have already been damaged.

Here are a few examples of natural water purification, which serve as illustrations of what wetlands can do.

Purifying Through Wetland Plants

The first interesting thing to look at is how wetland vegetation captures and breaks down pollutants naturally. TheEverglades filtration marshesis one example of how the biological process of plant uptake can be harnessed to strip excess nutrients from water at a landscape scale.

Cattails, reeds, and rushes are being sought as powerful living filters for the removal of excess nitrogen and phosphorus from agricultural runoff, and simultaneously produce habitat for fish, waterfowl, amphibians, and other wildlife, as well as other benefits such as flood control, shoreline stabilization, and carbon storage.1At constructed wetlands in the UK, for example, they are looking at how reed beds turn polluted mine drainage into clean water.2Seagrass meadows are also being explored for their potential to filter coastal waters and trap carbon.3

Natural purification also involves using soil microorganisms to break down other waterborne contaminants. Biofiltration through sand and gravel layers is now used in place of chemical treatment in many water systems to remove organic pollutants from runoff. Microorganisms living in the root zones of wetland plants degrade contaminants into harmless compounds. This is one of the most effective biological techniques currently available to remediate polluted waterways.

A range of natural enzymatic processes can also be used within treatment systems to reduce the number of harmful pollutants within a watershed. (Natural enzymes have also been discovered which could help to combat other forms of pollution — there is a oil-eating bacterium, for example.)

In the wider environment — along riverbanks and around agricultural fields, there are also other natural solutions that can help clean the water. Planting more riparian buffer strips can help to filter runoff before it reaches streams. But mosses have been shown to be effective indicators of water quality in mountain streams. And certain moss species are considerably more capable of absorbing heavy metals from flowing water than other plants.4.

Nitrogen, phosphorus, and sediment are trapped by wetland soils and plants, offsetting many tonnes of pollutants per year. This has led to the creation of constructed treatment wetlands — designed marsh systems used as "nature's kidneys for degraded landscapes," already employed across the United States, Europe, China, India, and Australia.

One constructed wetland is said to be equivalent to 275 acres of natural marsh — not only filtering water but also ridding it of harmful substances and recharging groundwater. Placement of these systems close to agricultural sites and along degraded rivers will help clean up the water that we drink.

Purifying Water

Natural purification using soil bacteria is being increasingly used in the decontamination of polluted groundwater using biofilters and permeable reactive barriers. And surface water can be decontaminated using constructed wetland methods using plants and microorganisms. Aquatic invertebrates such as freshwater mussels are also being investigated for their ecological functions and potential for natural water filtration in contaminated streams5.

Water can also be cleaned through the agency of riparian buffer zones and floodplain wetlands6. Rain gardens and other green infrastructure features can capture runoff from hard surfaces like parking lots and prevent contamination of nearby streams. Using wetland plants for water purification is known as phytoremediation.

Purifying Soil

Certain fungi can also be used in habitat restoration and soil remediation. Using mushrooms for remediation is often referred to as mycoremediation. Many studies have been published to emphasize the role of fungi in the remediation of contaminated soils by the process of biodegradation, biosorption, and bioconversion.7

Hyperaccumulator plants can also be grown on polluted sites (phytoremediation) to extract heavy metals and other pollutants from the soil.8By recognizing the ability of certain specific plants to accumulate toxic substances, landscapes that have been polluted can be restored.

Nature is a wonderful thing. Often, it can deliver all the solutions we need to repair the damage humanity is doing and has done. While there is still a lot of work to be done, it is clear that natural systems offer hope that we can clean up some of the mess we have made.

Of course, working out how we can avoid damaging and degrading wetlands and waterways in the first place is of vital importance. We cannot become complacent in reducing pollution. But as we face a future of growing water challenges, natural solutions can certainly help us find a pathway forward.

Wetlands International. "Natural Water Purification through Wetland Ecosystems." 2019.

Vymazal, J. "Constructed Wetlands for Wastewater Treatment." Water, vol. 2, 2010, pp. 530-549.

Duarte, C.M., et al. "The Role of Seagrass in Coastal Protection." Frontiers in Marine Science, 2021.

U.S. EPA. "Wetlands: Natural Water Quality Improvers." EPA 843-F-21-001.

Vaughn, C.C. "Ecosystem Services Provided by Freshwater Mussels." Hydrobiologia, vol. 810, 2018, pp. 15-27.

(Mitsch & Gosselink [2015]; Kadlec & Wallace [2008]; Vymazal [2011]; Zedler & Kercher [2005]).

U.S. Fish and Wildlife Service. "Wetlands Status and Trends." 2022 Report.

https://www.tums.ac.ir/1394/06/03/79%20(Lorestani).pdf-jnouri-2015-08-25-11-50.pdf