Bengaluru struggles to reuse water that can’t be discharged

While the city receives 3,000 million litres of water every day from the Cauvery river, treated water is wasted without proper treatment, monitoring, and regulations for re-use.

Bengaluru: An apartment in North Bengaluru is facing a problem: its sewage treatment plant (STP) breaks down periodically, and residents have to put up with stinking toilets when the faulty STP sends untreated water into the apartment's dual plumbing system.

This happens in many apartments, especially those that lack the space, willpower and leadership to handle water treatment in-house. The Karnataka government has mandated that every project with more than 120 units must treat its own sewage. The number was 50 or more apartments at one point, and most smaller apartments struggled to handle it.

A member of the association of an apartment in North Bengaluru explains how this happens. 

“When a project comes up, the builder goes and submits the documents to the pollution control board. The board reviews the papers and grants permission. After the building is complete, the KSPCB grants consent for operation after inspecting the STP in a non-working condition, because not all units would have been sold by then.

“When more than 60-70 per cent of the units are sold, apartment associations are formed. The builders hand over the STP and wash their hands of the project. The residents struggle without knowing the technology and operational pitfalls,” he says.

Two to three years down the line, the apartment associations realise that the STP does not have enough capacity. By then, they are left to deal with the situation on their own. Under-capacity STPs are one of the biggest problems plaguing water treatment in apartments, he adds.

Sharing of expenditure and availability of space become the next big problems to address if the association wants to upgrade the STP. Most builders do not support any such step. Associations are left in the lurch, having to find various water treatment consultants and conduct trial-and-error.

“When marketing projects, builders ignore STPs. They do not even know what technology they will use. But once the project is fully operational, STP becomes the most important part of the project,” he adds. “There is no liability on the builder. The government should mandate a liability of 10 years on the builder as well.”

He explains how the treated water is handled. “Treated water should not be let into stormwater drains or the ground according to the rules. There are only two options for extra treated water left after flushing and gardening: You either give it to someone who wants to take it, or discharge it to the ground or stormwater drain.”

According to him, there is no reliable system for using treated water in construction. Some companies install treatment plants in communities and sell excess treated water, but they need takers, and the systems are yet to be developed.

Overcoming the problem: A positive story

Srinivasan Sekhar, a water consultant based in Bengaluru, who faced the same issue in his community, shares a success story: TZed Homes, a 4-acre villa community in Whitefield with 78 flats and 18 villas, faced similar problems: in 2008, the association was formed, the builder’s maintenance period had ended, and the residents were left in a lurch. 

They engaged an STP consultant and understood how an STP operates. A few residents took an active interest and built a robust system in which STP water is passed through many pre-filters, then to the Reverse Osmosis plant, which clears the borewell water for the community. The water is now used for drinking and cooking. “We have many prefilters and a UV filter to ensure that even if one of them does not function, others stand in and water quality does not get affected,” he says. 

If there is any issue with the water quality, people are asked to boil the water and use it, and the problem is quickly fixed. Chlorination is then done to clean the pipes. This happens rarely. The annual maintenance contract ensures weekly water quality checks.

“First use is for gardening, housekeeping, mopping the floors and car cleaning. The rest of it goes to the RO unit,” he says. Maintenance is minimal; we only need to change the filter media periodically. A filter in the entrance of the STP collects any plastic or nonbiodegradable items, which are separated,” Sekar adds.

Changing the mindset was a challenge, but the community accepted it when a few dedicated members bathed in the treated RO water output and drank it in front of everyone. The community does not need any water from outside, as it also has rainwater harvesting.

This system in T-Zed Homes became operational in 2012. However, thirteen years later, TZed Homes remains the only community in Bengaluru to use treated water for daily household needs. “There were other builders and communities interested, but the interest waned easily. It is about the mindset,” Sekar sighs.

It's all in the mindset

Tarun Kumar, a STP consultant based in Whitefield, says a builder was interested in using treated water to drink. He built the infrastructure, but the resident community did not accept it due to a mindset issue. 

“Three problems affect the treated water reuse in household needs: Technology has to be robust; It should be economical, and the mindset needs to be progressive,” he observes.

Suhail Rahman, founder of a Bengaluru-based developer company, who tried to implement a system to use treated water for drinking, agrees that the main challenge is the psychological barrier to using recycled water for purposes involving skin contact.

"We have had a project running for the last five years. The RWA has discontinued tertiary treatment for this reason. Two more projects are being implemented,” he adds.

“Technologies are available for really high-quality water. We need regulations to help overcome this barrier. Technologies that give real-time data on water quality parameters will bolster the confidence of the user,” he adds.

“Running a conventional STP is highly technical. It requires a dedicated manpower round the clock. Pumps and motors break down periodically. In case of failure of the standby motors, the STP stops functioning, leading to a foul smell in the area,” he explains the operational challenges in running conventional aerobic STPs.

Does the solution lie in technology?

Rahman says that anaerobic STP technologies are available that do not present these challenges. “They need no pumps or motors, and no need for electricity—therefore, no breakdown. It does not require a round-the-clock staff and does not use chemicals. Overall, it's like a set-it-up-and-forget-it system that requires minimum supervision. Whereas a conventional STP is like a toddler, it requires constant monitoring,” he explains.

Alternative technologies can be a solution to cost-conscious RWAs or builders, says Tarunkumar. He has developed a sewage treatment system that mimics a cow’s stomach, where bacteria break down the sludge and clean the water. The space needed is double the regular STP, but the advantages are many, he adds.

Tarunkumar says his patented system, developed with IIT, Jammu, has zero maintenance cost, low maintenance cost, and zero electricity cost. “The sludge needs to be removed once every two years. This can result in huge savings,” he adds. 

A conventional STP can cost Rs 45,000 per kilolitre, while his method can cost Rs 60,000. However, later, operational expenses can go up upto Rs 30-50 per kilolitre, while his method costs Rs 2 per kilolitre, explains Tarunkumar, adding that the scope for savings post-installation is greater and that no regular maintenance is needed.

Other major problems

There is another major problem: Bengaluru lacks trained STP operators. The Environmental Management and Policy Research Institute conducts need-based training for STP operators if more than 15 people are interested. But the sector is not organised enough to conduct such workshops.

This lack of training and the unorganised nature of STP operations have resulted in manual scavenging and even deaths due to carbon monoxide poisoning, because standard operating procedures were non-existent and safety protocols were not followed. This has only been counterproductive to the cause, due to community residents' fear of the risky nature of STP operations.

The quality of the treated water is not uniform either. Various technologies operate in different ways, and some firms refuse to share their exact methods of treatment and operation. This results in non-uniform water quality. The KSPCB officials tasked with monitoring water quality are unable to do it periodically due to a shortage of human resources.

Where does the water go?

Satish Mallya, president of Bangalore Apartment Federation, says more than 60% of the treated water is available in every project. Flushing needs about 30%, and 5% for gardening and other needs; the rest of it is available, and no one knows what to do with it. 

About 700 MLD water is available from private and public STPs, according to our research. The government now allows up upto 50% to be used outside the project, such as selling it to construction companies, data centres or IT parks for cooling solutions. However, no steps have been taken to make it happen,” he adds. 

“There are no dedicated pipelines laid or dedicated tankers provided to transport this water anywhere. The government has to educate, raise awareness, and create demand by mandating the use of treated water. We cannot do it; only the government has the power to do it. Someone has to create the market,” he explains. “Safety standards and Standard Operating Procedure (SOP) have to be created for treated water usage, as it has to be used immediately; it cannot be stored for long.”

Now the government is trying to discharge some of the water to a few lakes. For example, a tender was floated in March 2025 to lay dedicated pipelines to the Chikkathogur and Begur lakes, but the project's status is unknown. BAF has suggested to the government that the water be used to clean BMTC and KSRTC buses and to water parks.

So where is the water going? Many who spoke to DH admit that it is going to stormwater drains because it is not prudent to leave the treated water to the BWSSB sewage line. Thus, while the city receives 3,000 million litres of water every day from the Cauvery, water is wasted without the proper treatment, monitoring, and regulations for use.