New Delhi’s Hauz Khas Lake now flows dirt/pollution free thanks to Floating Wetlands

The Covid-19 pandemic raised the need for water as a defense against the virus but in India, 98 million people are still deprived of access to clean water. Slums in India portray a dark truth about water bodies where the lack of sensible drainage systems allow solid and liquid waste from households to collect in a pit or a water body. As urbanisation claims India by the root, it is estimated that 70% of surface water in India is unfit for consumption.


This story swims around the historic 13th century Hauz Khas lake that over the years had declined to a stagnant pool of algae-covered, foul smelling water. When Tarun Sebastian Nanda, a civil-environmental engineer, returned to Delhi from London, he came with a vision to create an impactful change. The solution came to him in the form of floating wetlands, a unique concept that revolves around plants. He started his own company EVOLVE.


In Hauz Khas Lake, the putrid smell of the water decayed by sewage, human waste and pollution was unbearable to walkers, visitors and workers. Viciously growing algae on the surface prohibited sunlight from penetrating into and purifying the lake. EVOLVE decided to bring a change to this and build a better India by using wetlands. The Floating Wetland Concept follows the idea of phytoremediation and uses various plants to remove and stabilise pollutants in land, air and water. The wetlands come in two variants: floating wetlands for lakes and ponds, and constructed artificial wetlands that are used in private farms or urban slums to treat and recycle wastewater in drains and sewage. The wetlands mimic nature to act as sentinels against various kinds of pollution.


His passionate efforts in rallying for this cause introduced him to social activist Debayani Panja. Their wetland project has been largely successful through a unique publicly funded and citizen-led project. Floating wetlands were introduced in the dirtiest pockets of the Hauz Khas lake under the “Adopt an Island” program. These allowed members of the public, schools, corporates, etc. to become a part of the revival tale of Hauz Khas Lake. These are designed using up-cycled plastic and topped with bio-media and various wetland plants.


Floating Wetlands: Floating Wetlands are a natural cleansing process where the float is made of recycled wire mesh, plastic bottles and reed-plants. The cozy little mesh is manually created and then pushed into the dazzling lake where impurities and algae lurk unchecked. The dangling roots of the plant creep over the edge and into the water where it acts as a perfect magnet for impurities that get sucked by their roots. Due to budget restraints, the team adapted two existing drains and converted them to water purifying wetland ecosystems to treat the incoming as well as the water ecosystem in the lake. This was the first time that a dirty drain was enabled such a clean transformation in a country that has several such on the loose.


EVOLVE has also installed a floating solar aerator or purifier combined with primary, secondary and tertiary treatments into one unified system while using faecal-sludge drying beds, vertical and horizontal subsurface flow wetlands, surface flow wetlands and wetlands that change their function depending on the lake level and incoming water lows. They have also contributed to the only public sewage water treatment infrastructure that has been partially built by citizens.


The inlet wetland in the lake has been operational since February 2019 and is currently filtering all the incoming partially treated and raw sewage. It traps all floating sewage and suspended particles which has helped with the removal of nearly all the odour and waste matter from the incoming water supply. It is also the first time in Delhi that a floating solar aerator has been installed in a water body and a boat helps the team cross the lake for maintenance or repair.


Constructed or Artificial Wetlands are meant for drains and sewers that require division of land to create channels. It includes laying inlet pipes and any additional design before filling it with water and vegetation. Sewage and drains get their own constructed wetland in areas that do not require additional digging and natural ways to clean the water are explored. Constructed wetlands include inlet filtering, creating bunds and channels to allow flow of the water, and a pond around which they make these natural cleansing resources.


The first ever wetland in Delhi that treated a lake in a slum dwelling was created by Tarun Sebastian Nanda in 2014, and later became a model solution that was replicated by various authorities across the city.


The floating wetlands process has been tweaked over the years to make it vandal and thief resistant and Hauz Khas Lake project is today Delhi’s largest lake revival project. EVOLVE's method has also been adopted by the Delhi Jal Board who have begun to take cognisance of the issue on a larger scale. Tarun Nanda’s hopes to revive and clean waterbodies is not just a boon for the people but also for wildlife that no longer have to tread the dirt in Hauz Khas Lake.