A Closer Look at Nature’s Water Purifiers


From chemicals to plastics, it’s no secret pollutants end up contaminating streams, lakes, rivers and oceans worldwide, making water toxic both for the long-term ecosystem, and humans. 

According to the World Health Organisation, at least 2 billion people worldwide drink water from a source contaminated with faeces. And the reasons for water pollution are myriad: organic contaminants can be anything from viruses to bacteria, and chemical pollution can be caused by industrial runoff into waterways, or agricultural runoff from pesticides that cause an overflow of nitrates and phosphates.

With the pressing need for long-term solutions, many are looking at the role low-tech initiatives have in tackling this environmental problem. Namely, remediation approaches that are a little bit closer to home – thanks to nature. And whilst we are busy building hydration solutions, it’s worth taking a closer look at the way nature’s water purifiers are a step forward in tackling polluted water for now.

Floating Purification Islands

A significant consequence of water pollution is the growth of harmful algal blooms that spread across lakes. These masses of algae carry water-borne toxins that disrupt the ecosystem they inhabit. They also act as an impenetrable layer on top of the lake, blocking any oxygen or sunlight for the aquatic life below. 

According to the Food and Agriculture Organization of the United Nations, nitrates – a substance particularly harmful to infants – are the most common chemical contaminants in the world’s groundwater aquifers.

In Fish Fry Lake near Montana, United States, high levels of nitrates and phosphorus – a common ingredient in fertilisers and animal waste – caused this same overgrowth of algae, making the lake devoid of much life. And in South Delhi, India, the Hauz Khas Lake was threatened by masses of pollutants from sewage plants, also leading to large growths of algal blooms, as well as a significant decrease in size from 125 acres to a mere 15. 

And it’s not just lakes. According to the Food and Agriculture Organization of the United Nations, nitrates – a substance particularly harmful to infants – are the most common chemical contaminants in the world’s groundwater aquifers. It is estimated that 38 percent of the European Union’s water bodies are under pressure from this type of agricultural pollution. 

The solution for both Fish Fry and Hauz Khas lakes was an arguably simple initiative: floating rafts with plants – or in other words, makeshift wetlands, sometimes called nature’s own purifiers

The way these small floating wetlands naturally purify water is in absorbing the nitrates, phosphates and other heavy metals that create algal blooms in the first place. In Delhi, the Delhi Development Authority worked together with an environmental engineer to treat the contaminated lake, focussing on a process of filtration, absorption and uptake of nutrients into the wetland plants. The wetlands are also sustainably constructed out of recycled wire mesh, drainage pipes and used water bottles on which the plants are placed. All of which work to filter the water naturally.

It is a local approach that has also been picked up in Brooklyn. In a sustainable effort to tackle the polluted waterway of the Gowanus Canal, a “floating island” was also constructed, made up of bamboo, woody plant material, water hyacinth rope, shredded plastic, coconut matting and oak cork.


The connection between deforestation and diminishing clean water supplies can be highlighted in the Green Belt Movement, a grassroots initiative that has planted 51 million trees since 1977. 

Targeting land in Kenya that had become increasingly arid from trees being cut down, the Green Belt Movement began a tree-planting program, in which locals were taught how to plant tree seedlings. 

 “If you destroy the forest then the river will stop flowing, the rains will become irregular, the crops will fail”
–  Professor Wangari Maathai.

An empowering initiative for locals, tree-planting encouraged more water for what were becoming rapidly dried-up streams. And most importantly, a lot of that water was clean and purified, filtered from tree to stream, thanks to trees serving as natural sponges that collect and filter rainfall. 

In Comoros, East Africa, however, there is no resolution as of yet for their water supplies. Despite receiving more annual rainfall than most of Europe, deforestation has threatened their once-thriving rivers. The water trees and plants would normally collect and feed back into both the ground and rivers, is dwindling. Which emphasises how the planting of trees, whilst low-tech, is crucial to both guarantee clean water and upkeep the natural water cycle that maintains water levels. 

Aquatic Life

The least scalable of water-cleansing measures might be aquatic life. More specifically, the Chivita snail found in the Bacalar lagoon, Mexico. 

A lagoon famed for its seven different colours, Bacalar owes much of its clarity to this particular inhabitant: a herbivorous and detritivorous snail that eats dead organic matter and naturally cleanses the lagoon, keeping its waters clear. 

The Chivita snail has in recent years, however, become endangered due to being overfished, resulting in questions as to whether a 10-year ban should be implemented by the Mexican government, and whether an increase in aquaculture farms should be encouraged.

And whilst the lagoon for now remains crystal clear, what’s not clear is whether Bacalar will be a future example of water pollution as a consequence of human action. 

Aquatic Plants

Thriving on the water’s surface, aquatic plants can play a key role in environmental protection and upkeep, particularly when it comes to metal contaminants.

Toxic heavy metals such as mercury – which, according to the World Health Organization lead to negative effects in the kidney – can be reduced by aquatic plants like water hyacinths. In fact, water hyacinths are even recommended to remedy industrial wastewater, domestic wastewater and sewage effluents. Recognised as having a sophisticated ability to tolerate an extremely polluted environment, they absorb contaminants like mercury, as well as copper and lead. 

Similarly, duckweed is also known to eliminate a variety of heavy metals, as well as diminish nitrogen from ponds by absorbing and taking up ammonia. It can also easily inhibit the growth of algae and fungi in different ponds – a potential prevention of the algal blooms that occurred in Delhi and Montana, for example.

By removing heavy metals through absorption, contaminants in wastewater are effectively mitigated through aquatic plants, which underlines their innovative potential in water cleansing.

By Lauren — May 7, 2020
The information contained in this article is provided for educational and informational purposes only, and should not be construed as health or nutritional advice.

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