Science Behind a Constructed Wetland To Treat Sewage - (E)

Freshwater is scarce very scarce. In times to come, it may become more precious than gold if humanity cannot control its pollution. Over seventy percent of Earth’s surfaace is covered with water, but only 2.5% of this is freshwater. In this episode, we visit Neela Hauz, a lake in New Delhi that was restored to its near-pristine glory using the ecological principles of treating sewage through a technique called the constructed wetland approach. Conserving freshwater is critical since most land-based life depends on freshwater availability. Urban settlements generate a lot of polluted water, which gets channelled into sewage. One way to clean up sewage is by using sewage treatment plants that are expensive to construct and need lots of electricity to run and maintain. Scientists have developed an ecological environment-friendly solution to clean sewage water using a constructed wetland. Here raw sewage is passed through a natural storage pond, and then the solid waste is removed. Subsequently, the water flows down a channel merely using the force of gravity. Here pebbles and barriers create small rapids which help aerate the water, and the biological oxygen demand is controlled by naturally adding oxygen to it. This water can then flow through a patch of plants, aptly called a constructed wetland since humans plant it. Here the roots and the community of plants passively filter the water. Aquatic plants like Typha, Phragmites, Salvinia, Sedges along with Blue-Green Algae, Green Algae and Mosses help clean the water. In addition, Molluscs and tiny insects also play a role in cleaning the water. This system needs no input of electricity and is very environment friendly. At Neela Hauz, almost one million litres per day of sewage is converted from its stinky black condition to near-transparent water, and it has been functioning since 2016. An ecosystems approach for treating sewage, but can this experiment be replicated on a large scale? Watch the episode to know more!

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