In the early months of the COVID-19 pandemic, handwashing advisories echoed across homes, hospitals, and hostels. Clothes were washed more often. Buckets filled faster. Laundry loads increased. Detergent use surged.
While most of us were focused on staying safe, Prof Kasturi Dutta found herself thinking about something else: where was all that soapy water going?
“During COVID, we saw a dramatic increase in washing, be it clothes or hands,” she recalls. “Reports were highlighting the sharp rise in surfactants entering wastewater systems. That is when we began thinking seriously about treating laundry-related wastewater specifically.”
The wastewater treatment system cuts surfactants and COD to ~1 ppm, meeting Bureau of Indian Standards safety limits for reuse. Photograph: (Divyani Kumari)
At the National Institute of Technology Rourkela (NIT Rourkela), where she serves as an associate professor in the department of biotechnology and medical engineering, that concern began to take shape. Today, near the campus dhobi ghat (traditional open-air laundry area), two large cylindrical tanks stand connected by pipes and wires, transforming detergent-rich wastewater into reusable greywater.
A question that began years before the pandemic
The idea behind this project had taken shape years before the pandemic.
During her postdoctoral research in Taiwan, Prof Dutta immersed herself in wastewater treatment. She worked on municipal systems and helped develop a locally built reactor that cleaned polluted liquid waste from household wastewater while also generating biogas. The work showed her that waste could be treated and turned into something useful at the same time.
When she joined NIT Rourkela in 2015, she brought that thinking with her.
In 2023, the opportunity to apply it arrived. Through CSR funding from the Higher Education Financing Agency (HEFA), the team received support to build and test a sustainable wastewater treatment model on campus. The funding focuses on promoting innovation and socially relevant technologies within higher education institutions.
The dhobi ghatproject became a practical way to turn that long-held vision into action by addressing an everyday water challenge on campus.
“We selected dhobi ghats as a focus area because water scarcity is a major issue and laundry workers require clean water to wash clothes properly,” says Prof Dutta. “The idea was simple: if we can treat and reuse laundry wastewater, we can reduce freshwater demand and provide a sustainable solution.”
What happens when detergent enters drains
It is easy to look at soapy water swirling down a drain and assume it disappears without consequence.
But laundry wastewater carries more than foam.
Detergents contain surfactants, phosphates, and sulphates. When this water enters drains untreated, it raises something called chemical oxygen demand, which refers to the amount of oxygen needed to break down pollutants in water. If that demand becomes too high, oxygen levels in lakes and rivers drop, putting aquatic life at risk.
On the NIT Rourkela campus, the dhobi facility uses about 1,400 litres of water each day. Until recently, much of that water would simply flow away. The storage tank that now collects wastewater from the dhobi ghat can hold up to 1,000 litres at a time.
A surge in detergent-laden wastewater during COVID led Prof Dutta to create a system that reuses dhobi ghat water, easing water scarcity during summer. Photograph: (Divyani Kumari)
To make use of this, the research team installed a pilot treatment system capable of handling 300 litres within 24 hours. In practice, the constructed wetland–microbial fuel cell system helps reuse between 500 and 1,000 litres of treated greywater daily.
Out of the 1,000 litres used each day, this translates to a reduction of roughly 85 to 90 percent in freshwater demand, depending on weather conditions and evaporation rates.
Just as importantly, the treated water meets safety standards. Surfactants and chemical oxygen demand are reduced to around 1 ppm, which falls within the permissible limits set by the Bureau of Indian Standards.
“Often in research, systems are either tested only in the lab or directly envisioned for massive facilities like the famous dhobi ghats of Mumbai,” Prof Dutta explains. “But jumping directly from lab scale to extremely large scale is difficult. Our approach was to develop a real-time, medium-scale system that could realistically be replicated.”
Inside the tanks: A constructed wetland in action
At first glance, the setup looks simple. Two black tanks sit beside the laundry area, connected by pipes. It does not resemble a high-tech laboratory installation. Yet inside, it works like a small, carefully designed ecosystem.
The system begins with an underground tank that collects wastewater from thedhobi ghat. From there, the water is pumped into two treatment units known as constructed wetland–microbial fuel cells. A separate tank stores the treated water once the process is complete.
Inside each unit, the layers are arranged with intention. Large graphite chunks form the base. Above them lie layers of gravel, sand, and soil. On the surface grow sturdy wetland plants, Canna species, selected because they can thrive in waterlogged and polluted conditions.
As the wastewater slowly moves through these layers, each one plays a role. Gravel and sand trap solid particles. The roots of the plants absorb certain pollutants. Microorganisms living within the lower layers break down detergent compounds.
Canna species were chosen for their resilience in polluted, waterlogged conditions and strong pollutant uptake ability.
Together, these materials and living organisms clean the water in a way that mirrors how natural wetlands purify water in the wild.
“In essence, the system is a mini artificial wetland built inside tanks,” says Prof Dutta. “Plants and bacteria work together to clean laundry wastewater, and special bacteria called electrogens also generate a small amount of electricity during the process that further helps with cleaning the water.”
Where microbes generate electricity
Hidden beneath the layers of gravel and soil is the part that sets this system apart.
The lower section of each tank has very little oxygen. This creates the right environment for a special group of bacteria known as electrogenic microbes. In simple terms, these microbes can produce a small amount of electricity while feeding on pollutants. This oxygen-poor region functions as what scientists call an anode, where these microbes grow and work.
As they break down organic waste in the detergent-rich water, they release tiny charged particles called electrons. These electrons travel through a wire to another section of the tank that has more oxygen, known as the cathode. That movement generates a small electric current, referred to as bioelectricity.
Plants and microbes clean laundry water, while electrogenic bacteria generate bioelectricity that indirectly helps with purification. Photograph: (Divyani Kumari)
In laboratory conditions, the system produced 1 volt and above. On campus, under real field conditions, the team has measured an average of about 600 millivolts. During winter, the voltage drops because lower temperatures slow down microbial activity.
“When we compared a regular constructed wetland with one integrated with a microbial fuel cell, we observed better pollutant removal in the integrated system,” says Prof Dutta.
At its core, the idea is simple. The microbes feed on pollutants present in the wastewater. As they do so, they help clean the water and generate a small amount of electricity in the process.
A living system that changes with the seasons
For Divyani Kumari, a PhD scholar and environmental microbiologist working under Prof Dutta, the system feels dynamic.
“I consider this entirely a living system, not a fixed artificial product,” she explains. “Microbes grow differently, plants behave differently, and the system responds dynamically to environmental conditions. Because of that, we cannot guarantee maximum output at all times, but we can ensure that the minimum purification standards are consistently met.”
The team continues to observe how the system performs over time. At present, the water remains inside the treatment units for 48 hours before being released. This duration, known as hydraulic retention time, allows the plants and microbes enough time to do their work.
A CW-MFC system combines wetland plants and electrogenic microbes to treat wastewater while producing bioelectricity. Photograph: (Divyani Kumari)
Seasonal monitoring is ongoing to understand how stable and efficient the system remains across the year. In the coming months, the researchers plan to test shorter retention periods of 24, 12, 6, 4, and even 2 hours to see how quickly the water can be treated without compromising quality.
Weather plays a role as well. In summer, warmer temperatures encourage faster microbial activity, which supports quicker treatment. In winter, when temperatures drop to between 3 and 10°C, the process slows. Even so, the treated water continues to meet the required quality standards.
From drainage to daily relief
The treated water remains greywater and is not potable. It is suitable for washing clothes, cleaning floors, gardening, and general utility use. Approximately 15 to 20 people, including dhobi workers and associated households, benefit daily from the recycled water system.
Pyarelal Rajak, who runs the campus laundry service, sees the difference each day. On busy days, he uses up to 2,000 litres of water. Summer months often bring shortages. “There was no way to store dirty water before; it would just drain away,” he says. “Now, wastewater from his dhobi ghatis collected and treated.”
“Kasturi mam and her PhD students worked very hard on this. Right now, the system is helping, I wish it were bigger to handle much greater demand,” he adds.
A pipe now connects the purification tank back to his washing area, creating a circular system where treated water flows back into use.
The road to replication
For now, the system remains rooted on campus.
No municipal authority or government body has formally signed on to replicate it yet. Still, the idea has begun to travel. Within NIT Rourkela, the project has drawn positive attention, and early conversations point towards the possibility of installing similar units in campus hostels as part of decentralised wastewater treatment.
Cost remains one of its strongest arguments. The full installation on campus cost approximately Rs 2 lakh, including the underground collection tank and supporting infrastructure. The treatment unit itself, the two tanks with their layered ecosystem and electrodes, costs around Rs 30,000.
The current CSR-backed funding will continue until 2026. After that, the team plans to apply for competitive research grants from government and private agencies to sustain and expand the work.
Its low installation cost and simple design make the system affordable, easy to maintain, and scalable. Photograph: (Divyani Kumari)
Prof Dutta sees the model as practical for wider use because it does not demand heavy capital investment or constant expert supervision.
“One trained caretaker could manage multiple units,” Divyani explains. The role would involve adding water in batches, releasing treated water after the defined retention period, checking plant health, and ensuring the system does not overflow. It requires attention and care, but not complex technical expertise.
With structured funding and institutional backing, the team imagines these systems installed in community laundry spaces and urban neighbourhoods where water stress shapes daily routines. The vision is simple: a decentralised, low-cost system that sits close to where water is used and ensures it does not go to waste.
Looking ahead
“Even if this system helps reduce only a portion of the water stress we are currently facing, that contribution would be significant,” says Prof Dutta. “Seeing it adopted at scale would be both professionally rewarding and personally fulfilling.”
For Divyani, the experience carries personal meaning. “It feels similar to installing a rainwater harvesting system,” she reflects. “There is a sense of responsibility and pride in conserving and reusing water. Even if it never becomes a commercial product, I would still be happy to implement it at a personal scale. That is my biggest takeaway.”
In a country where freshwater stress shapes daily routines, practical solutions matter. On one university campus, a system built with plants, microbes, and sustained research is already reducing freshwater demand by up to 90 percent in a small corner of Rourkela.
Sometimes, change begins at the edge of a dhobi ghat.
