Follow the water down.

Scroll to travel through a system that cleans what a wetland leaves behind.

The drain

The drain.

Twenty minutes from our school is a village called Chhilora. It has no drainage channel at all. Every time a field is watered, the fertiliser and pesticide the crop did not absorb washes into the shallow water that hand pumps draw from, and into the village pond.

Irrigation water running off a field along an open earth channel — Flood irrigation: whatever the crop doesn't take runs off.

What that does

What that does.

Children drink from those hand pumps before school. We collected that water and had it tested. It came back with sulphate, lead, pesticide and insecticide in it. The pond had turned green and the fish were gone.

A team member collecting a water sample from a village hand pump — Sampling a hand pump

A village pond covered in green algae — The pond, gone green

The wetland

The wetland.

Constructed wetlands are the affordable answer, and the government is already building them. Plants, gravel and bacteria clean water with no electricity at all. But a wetland only does half the job.

The wetland design is the work of CEMDE, University of Delhi. Our part is the stage that comes after it.

A wetland channel with water flowing over a low weir

The gap

What the wetland misses.

Phosphorus
Feeds algae until ponds turn green.
Ammonia in winter
The wetland's bacteria slow down in the cold.
Heavy metals
Stored in the mud, not removed, and rain can wash them out again.
Pesticides and medicines
Pass straight through.

Bed one

Bed one — zeolite.

Soaks up ammonia. It works by chemistry, not bacteria, so it keeps going through winter.

Bed two

Bed two — ferric oxide.

Just rust. It holds on to phosphorus, arsenic and lead, and when the bed is swapped out those metals leave the site instead of building up in the mud.

Bed three

Bed three — biochar with titanium dioxide.

Charcoal full of holes too small to see, which traps pesticides and medicine residues.

The beds are raised and open to the sky. We believe sunlight falling on the titanium dioxide breaks apart what the charcoal has trapped, so the bed cleans itself instead of becoming someone else’s waste.

That is still a hypothesis. We are testing it now, with sun-exposed beds against identical beds kept in the dark.

Clean water out

Clean water out.

This is the stage that catches what the wetland misses.

Vedant and Teerthoraj pouring water through the SPARC prototype outdoors — The first prototype column, being tested outdoors.

Walk through it yourself

Try the simulator.

Open in a new tab

Drag to look around, scroll to zoom, W and S to move along the drain.

In our own words

Watch it.

Taking it to the experts

What a wetland scientist wrote to us.

Written feedback

Inspiring Young Minds Through Nature-Based Solutions

Two talented Class XI students, Teerthoraj Chatterjee and Vedant Agrawal, accompanied by their mentor, Mr. Vivek Bhardwaj of Brainz Edu World, Meerut, visited Neela Hauz Biodiversity Park to learn about nature-based solutions for sewage water treatment.
During their visit, both students showed remarkable curiosity and a keen interest in understanding the Constructed Wetland System (CWS). Their thoughtful questions reflected their understanding of the system and their genuine enthusiasm for exploring practical, nature-based approaches to water treatment.
I explained how they could replicate a similar system on a smaller drain in Meerut, monitor its performance, and evaluate its effectiveness in improving water quality. We also discussed the possibility of conducting further experiments by incorporating a charcoal layer at the final stage of filtration to study its impact on various water quality parameters.
It was encouraging to interact with such bright young minds who are eager to connect scientific knowledge with practical environmental solutions. With the right guidance and experimentation, students like them can play a meaningful role in promoting sustainable water management and environmental conservation.

Yasir Arafat

Scientist-B, Biodiversity Parks Programme
CEMDE, University of Delhi