Boson Whitewater — a water utility venture that converts treated water from sewage treatment plants (STPs) into high-quality potable water — has partnered with the non-profit Biome Environmental Trust to launch India’s first indirect potable water reuse project. This innovative initiative, located in Devanahalli, 40 kilometres northeast of Bengaluru, uses managed aquifer recharge to achieve sustainable water reuse.
According to the participants [of this project], the project produces 6.4 lakh litres of potable drinking water per day, adhering to BIS (Bureau of Indian Standards)-10500 standards. The clean water directly benefits thousands of residents in the Devanahalli municipality.
How does this work?
Simply put, treated wastewater from a sewage treatment plant is first pumped into Bagalur Lake, where it is diluted with rainwater. This water is then directed to Devanahalli’s Sihineeru Kere Lake through a pipeline, further diluted with rainwater, and subsequently filtered through the earth to recharge the aquifer. The water is then picked up from the aquifer through a dug well and shallow filter borewells, treated, and then supplied to the town residents.
Why is this an indirect potable water reuse project?
This project uses an environmental buffer like a lake for dilution with rainwater and/or a groundwater aquifer for earth filtration. This water eventually goes through a final treatment stage before it is supplied to residents.
What’s more, the project is part of a larger effort to rejuvenate 65 lakes in Bengaluru employing treated wastewater and rainwater.
According to the project, “It involves reviving an old well and digging borewells to access the aquifer, along with the installation of water treatment plants in two phases. Now, the system provides 6.4 lakh litres of water daily, helping supplement the domestic water requirement of 45,000 residents in Devanahalli. This was made possible through the collaboration of many organisations — including Carl Zeiss, Rotary South Parade Bangalore, and Wipro Foundation.”
Going further, it claims that the project is energy-efficient, using just 0.25 units of electricity per 1,000 litres, and follows the Union Government’s AMRUT 2.0 guidelines, thus serving as a model for future urban water management. In 2021, the Union Government launched the AMRUT 2.0 scheme to “augment infrastructure for water supply, sewerage and septage management and rejuvenate the water bodies aiming to improve the quality of life”.
Speaking to The Better India, Vikas Brahmavar, co-founder of Boson Whitewater, says, “For AMRUT 2.0, there are specific guidelines on making the project commercially viable and ensuring water quality, which means we’ve taken careful steps to maintain high water standards and an appropriate design. In terms of power usage, we cannot have a complex, elaborate treatment system that consumes a lot of power for water treatment.”
“We only use a few pumps to move water through the system, keeping power consumption low. Now, imagine if we had to use RO (reverse osmosis) and UF (ultrafiltration); it would become too complex in terms of power requirements. Since the water from the well and the shallow aquifer meets IS 10500 standards, we’re able to treat it with a simple four-stage treatment process to ensure safety, making it suitable for domestic supply,” he adds.
Vishwanath S, a civil engineer, water management expert and advisor at Biome Environmental Trust, notes, “Devanahalli town relies heavily on deep borewells for its water supply. Through this project, we aim to revive the local lake, recharge groundwater, and explore how a town can become self-sufficient by using both local water sources and treated wastewater. The project has the capacity to meet Devanahalli’s 5.4 MLD (million litres per day) water demand.”
[1 MLD (million litres per day) is equal to 1,000 KLD (thousand litres per day)]
“In Phase 1, a water treatment plant was installed to provide 240 kilo litres (2.4 lakh litres) of water daily. In Phase 2, the project expanded with the addition of four more filter borewells, a reconstructed 60 kilolitres (KL) sump, and a new 400 KLD water treatment plant. The system now delivers 640 KL (6.4 lakh) of water daily, benefiting the Devanahalli residents,” he adds.
Vikas notes, “Our vision is to create a sustainable third source of water by utilising every drop of wastewater generated in our cities.”
Now, let’s break down the project into its finer details.
How did we get here?
What Biome has been doing is this:
There was an old well near the Sihineeru Kere lake, estimated to be over 100 years old. Due to the lake’s dryness and lack of water seepage into the well, people started using it to dispose of debris. Biome, in collaboration with the local panchayat, cleaned out this well in 2020-21.
“Once the well was cleaned and treated wastewater was directed to the lake, the well, situated about 25 to 30 feet from the lake, began to fill as water seeped through the earth from the lake. This natural earth filtration helped fill the well. Biome then tested this well water, which met the IS 10500 standards. Over time, the Indian Institute of Science (IISc) got involved, recognising the water quality and exploring how to make it usable for the public. Since the well water filtered through the earth, it was deemed safe,” explains Vikas.
Thus, a two-phase project was initiated. The first phase, completed a year and a half ago, was designed to recover 200 KL (2 lakh litres) of water daily. Water from the well was processed through disk filtration, activated carbon filtration (with high iodine value), UV (ultraviolet light disinfection) treatment, and basic chlorine disinfection before being sent to a sump.
This sump also received deep borewell water. In that area, deep borewells, which reach depths of around 1,000 to 1,100 feet, often contain fluoride and other contaminants, making the water usable only for bathing and similar purposes. Water from the sump was pumped to the entire Devanahalli town, which requires about 5.4 to 6 MLD of water daily.
“Biome envisioned that by meeting just 10% of the town’s water needs, they could demonstrate a viable model for small towns across India. In this way, where lakes and wastewater are available, communities could effectively use such resources,” notes Vikas.
Phase 1 was installed in July-August 2023, followed by a year of testing. Once it proved effective, Phase 2 was launched in August 2024. Now, both phases are operational, supplying 600 KL or 6 lakh litres of water per day.
“As the next phase, we are planning to replicate this process at Doddakere Lake, a large lake with multiple unused wells currently filled with debris,” he adds.
Understanding the flow of water from lake to lake
Water is treated at the government-operated STP called Hebbal Nagawara Treatment Plant (HN Valley Treatment Plant). From this plant, it is pumped to Bagalur Lake through a pipeline and then from that lake it comes to Sihi Neerukere Lake. There’s a specific reason they do this.
“The lakes often dry up, and the only way to refill them is by pumping treated wastewater. Government-run STPs are required to meet certain qualities so that the wastewater they treat can be pumped into the lakes. Only if that quality is met, the treated wastewater is sent to the lake,” says Vikas.
But why does treated wastewater require further dilution by rainwater in both Bagalur Lake and Sihi Neerukere Lake?
“Whenever the treated water goes to the lake, during the rainy season there is always dilution from the rain, and Bengaluru probably gets 47 or 60 days of rain across various months. So, based on this rain, there is always dilution in the lake. So, we do not purposefully do it, but the idea of giving it to the lake is to dilute it with natural water,” he adds.
As explained earlier, treated wastewater that is further diluted with rainwater is diverted to Devanahalli’s Sihi Neerukere Lake. Here, it is further diluted with rainwater, and subsequently filtered through the earth to recharge the aquifer.
“The Sihi Neerukere Lake will dry up if no water flows into it. Devanahalli always had problems with drought. Back in 2015-16, this lake almost went dry. The local governing body asked the Government to send the treated wastewater to the lake because it would go defunct. That was the initial purpose,” he says.
After this treated wastewater is once again further diluted with rainwater, it is subsequently filtered through the earth to recharge the aquifer.
For Phase 2, they used something called a shallow aquifer.
“So, instead of digging a borewell at 1,000 feet, you dig a filter borewell (shallow aquifer) at a maximum depth of 50 to 90 feet. Here, well water seeps again through natural filtration and enters the filter borewell. Filter borewells are essentially shallow borewells with pores in the pipe for filtering, and the plan was for about six or seven filter borewells, I believe,” explains Vikas.
“Water then undergoes another level of earth filtration before reaching another sump,” he adds.
So, for the second phase, they use shallow aquifer water from the filter borewells, directing it to the sump. “We added a more advanced treatment plant, where the disc filtration is now fully automated. This system includes a higher-grade activated carbon filter, multiple UV systems in parallel, and chlorine disinfection, after which the water is sent to the sump,” he explains.
“Previously, the sump received deep borewell water high in fluoride, contaminants, and dissolved salts. Now, these issues have decreased due to the shallow aquifer water, and the psychological barrier is also gone since multiple levels of earth filtration are used, making the water safe to supply to the entire village,” he adds.
The water is then picked up from the aquifer through a dug well and shallow filter borewells, treated, and then supplied to the town.
“The water quality meets IS 10500 standards. The TDS (total dissolved solids) averages below 500 ppm, compared to 1800 ppm in deep borewells, and contains no fluoride, unlike deep borewell water. Making things better, Devanahalli residents don’t pay for the water since the local government body supplies it for free,” he says.
If a similar model is successfully replicated across the city, then Bengaluru could better navigate its perennial water shortage issue. Besides offering the opportunity to prevent flooding, these lakes offer buffer spaces for the city to use its wastewater efficiently.
(Edited by Pranita Bhat; Images courtesy Boson Whitewater)
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