Should rural India drink urban wastewater?

One of the many lakes in Kolar that are being filled with Bengaluru's wastewater, Kolaramma lake in Kolar district is seen here covered in water hyacinth. Photo sourced from Anjaneya Reddy.


  • Touted as a shining example of India’s ingenuity, KC Valley project transports Bengaluru’s secondary treated wastewater to parched rural neighbourhoods in Kolar district.
  • Scientists and activists are apprehensive of the long-term effect of using treated wastewater, that may carry toxic heavy metals, to recharge groundwater.
  • While sewage treatment plant data assure all is well, experts say the hasty implementation of the project without necessary prior studies to foolproof it was a myopic move.

It is early August and Kolar is shades of brown and green. Unexpected showers in the previous months have lifted the spirits of the farmers here. Called the land of silk, milk and gold, Kolar district, 70 km east of Karnataka’s capital city of Bengaluru is known for its enterprising farmers and a variety of agriculture they practice. Bengaluru owes the seamless supply of fresh vegetables and milk to the farmers of this region. Almost every house here has a farm adjacent to it and livestock milling about.

Briefly interjecting the everyday mundaneness of farm life in Kolar was Csaba Kőrösi, the president of the United Nations General Assembly who visited the Somambudi Agrahara Kere or Somambudikere (kere is Kannada for lake), one of the biggest lakes in Kolar, with the then minor irrigation secretary Mrityunjaya Swamy, early this year. At the sight of the lake, plump and pregnant with wastewater from Bengaluru, a visibly elated Kőrösi publicly praised Karnataka government’s ingenious project utilising Bengaluru’s wastewater to recharge Kolar’s groundwater.

Chandramma, a local, couldn’t fathom that the smelly lake filled with “galeeju neeru” (dirty water) from the neighbouring city merits a visit from important world leaders. All she knows is that since the time the wastewater has come to her backyard, the water-storage sump in her house demands a wash once a month as against an annual wash. The people of Kolar have grown so suspicious of the water that it is now blamed for every new malady. Chandramma’s son Vinay plucks a handful of mulberry plants from their farm to show the suliroga (local name of a certain pest) that’s causing the leaves and buds to shrivel up. “We did not have this issue before. This water is causing it,” he said, pointing to the lake.

Chandramma (left) and her son Vinay. They live near Somambudikere, one of the lakes in Kolar that carries the wastewater of Bengaluru and are unhappy with the quality of water they are getting now for drinking and agriculture. Photo by Arathi Menon
Chandramma (left) and her son Vinay who live near Somambudikere, one of the lakes in Kolar that carries the wastewater of Bengaluru. They are unhappy with the quality of groundwater they are getting now for drinking and agriculture. Photo by Arathi Menon/Mongabay.

Somambudikere, like many lakes in this acute water-stressed region, had remained dry most of the year until the Karnataka government executed the plan to fill a network of 134 lakes in the district with 440 MLD (millions of litres per day) of Bengaluru’s secondary treated wastewater. Until the project, called Koramangala-Challaghatta Valley (or KC Valley) project, was implemented, the wastewater was flowing into Tamil Nadu through Dakshina Pinakini and South Pennar rivers causing much discomfort to the neighbouring state. As a result of Karnataka’s damage control measure to reroute the treated wastewater back to its own parched lands, the KC Valley project took shape in 2018. KC Valley is one of the three valleys of Bengaluru, the others being Hebbal-Nagavara or HN Valley and Vrishabhavati Valley.

Touted as a success within a few years of its implementation with no concrete data to support the claim, KC Valley inspired a similar project providing 210 MLD treated wastewater from Hebbal-Nagavara valley to the neighbouring district of Chikkaballapur in 2020. Another, Vrishabhavati Lift Irrigation Project, was announced recently to lift 243 MLD treated wastewater for Bengaluru Rural, Bengaluru Urban and Tumakuru districts.

Kolar’s water issues go way back, need better understanding

The water woes of Kolar district go back decades. With no rivers flowing in the district, or at an accessible distance from it, ancient dynasties created tanks or lakes as surface water reservoirs. With a little over 3,000 lakes (Central Groundwater Board 2009), the undivided Kolar district, before Chikkaballapur district was carved out of it in 2007, accounted for the most number of lakes in the state.

The lakes, designed in topographical sequence facilitating runoff harvest from upstream to downstream reservoirs in a cascading manner, served multiple purposes such as water supply for domestic, livestock and agricultural uses and groundwater recharge.

Between 1972 and 2011, there was a shift from grasslands and rainfed crop lands to eucalyptus plantation and irrigated cultivation, which the lakes fell short of appeasing, revealed a 2020 study. This change in land use reduced surface runoff and groundwater recharge by 30% and the irrigation demand of the district increased from 57 mm in 1972 to 140 mm in 2011. Borewells that could go great depths in search of water became Kolar farmers’ new darling. The study noted that the extensive use of borewells increased groundwater abstraction by 145% in this period.

Women walk past Mustoor lake in Chikkaballapur. Photo by Arathi Menon
Women walk past Mustoor lake in Chikkaballapur. Photo by Arathi Menon/Mongabay.

Historically, a major part of the irrigated area was next to these lakes but ironically, not one was being used for irrigation towards the latter part of the century. As per the 2009 estimate, a net sown area of 3,604 sq km was fully irrigated by over 90,000 borewells in undivided Kolar.

Modernity failed to do what ancient wisdom did — keep agriculture sustainable. Changing climate with erratic rain and repeated droughts exacerbated Kolar’s water stress and more borewells, some as deep as 500 MBGL (metres below ground level) were dug.

As a solution to this mounting water problem, the Karnataka government sanctioned Yettinahole Integrated Drinking Water Project in 2014 designed to lift 24.01 TMC water from west-flowing streams and transport it to water-stressed regions including Kolar and Chikkaballapur about 300 km away at a cost of Rs. 12,912.36 crores. While this project was mired in multiple environmental issues, another environmentally unsound KC Valley project, a joint venture of Bangalore Water Supply and Sewerage Board and Minor Irrigation department, was launched.

Is KC Valley project an environmental disaster in the making?

Mongabay-India visited eight lakes — three in Chikkaballapur district and five in Kolar district — which are a part of the KC and HN Valley projects. Much of the eight lakes were seen covered with water hyacinth, considered one of the top 10 invasive species in the world. “This is a clear sign of eutrophication,” said Nirmala Gowda of Bengaluru-based think tank Paani, which studies Karnataka rivers and collects data on them. Eutrophication is the process by which a water body becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus, and can result in an increase in toxicity of the water body and a decrease in biodiversity.

These nutrients are good for plants and agriculture but oxidisation of nitrogen results in nitrates that are harmful to humans, warn scientists. “When you let the high nutrient wastewater into the lake, the groundwater gets recharged. As the water travels underground, nitrogen gets oxidised to nitrates which are carcinogenic and can lead to diseases like cancer and kidney failure,” said scientist T.V. Ramachandra, coordinator, energy and wetlands research group, Indian Institute of Science (IISc), Bengaluru.

A study by Ramachandra and team near the wastewater-filled Varthur lake of Bengaluru found traces of heavy metals in vegetables grown around it due to contamination. “While the BWSSB’s sewage lines are expected to carry only household wastewater and some amount of commercial effluents, the clandestine dumping of toxic industrial effluents into sewage lines has been reported from Bengaluru,” said Gowda.

Men with lines and rods catch fish at Mustoor lake in Chikkaballapur district. The quality of fish in these lakes filled with treated wastewater from Bengaluru has gone down. Photo by Arathi Menon
Men with lines and rods catch fish at Mustoor lake in Chikkaballapur district. Residents say that the quality of fish in these lakes, filled with treated wastewater from Bengaluru, has gone down. Photo by Arathi Menon/Mongabay.

A fierce critic of the KC Valley project, Ramachandra said that he had given clear directions to the government on its execution when the concerned departments approached him for guidance in 2015. “From our experience of Jakkur lake rejuvenation, I had suggested integrating wetlands and algal ponds with the lakes as a cost-effective tertiary treatment for secondary treated wastewater but the authorities overlooked this suggestion and went ahead with discharging secondary treated wastewater directly into the lakes,” he said.

The Centre for Sustainable Technologies, IISc which claims to be monitoring the water quality regularly, said that while the treated wastewater from Bengaluru is of superior standards, local sewage lines are connected to some of the lakes which are contributing to the nutrients in the lake. “Some human activities around the lake like bathing and washing clothes also add to contamination. We are working on fixing these issues,” said assistant professor Lakshminarayana Rao.

Treated water quality data suggests poor performance of STPs

The wastewater that reaches the sewage treatment plants in Bengaluru typically goes through two steps of treatment. First, is the primary treatment where the suspended solids are removed. The secondary treatment involves suspended aerobic processes using aerobic microbes to biologically remove contaminants from water. This biological process, when done properly, ensures that 90% of Biochemical Oxygen Demand (BOD) and suspended solids (SS) are removed from the wastewater. Secondary treatment, however, does not remove traces of heavy metals that may enter the water through industrial effluents.

Rao told Mongabay-India that the project uses Soil Aquifer Treatment (or SAT) system that enables the treated water quality to improve underground. “The treated wastewater from the city is already of superior quality that meets National Green Tribunal standards. It is further cleaned through rainwater runoff and the SAT system,” he said.

A detailed map showing the KC Valley project by Paani
A detailed map showing the KC Valley project by Paani.

A 2023 report by Rao and his team says that apart from improvement in daily groundwater recharge, the project has resulted in good quality groundwater due to higher ground infiltration and a rise in groundwater tables. The report goes on to say that the availability of groundwater significantly improved agricultural, milk and fish productivity in the region. Rao acknowledged that the region had witnessed unexpected heavy rainfall from 2020-2022 which has contributed to the improved quality of groundwater but believed even in the absence of rainfall, the quality of the water won’t be worsened due to the SAT system.

While SAT is a wastewater treatment method used widely, its performance depends on local hydrogeological conditions and has certain limitations like unsatisfactory filtration of organic micropollutants, a need to regularly monitor its performance to avoid hazards, and more, according to a study. In the absence of necessary data, it is not known fully if the hydrogeological conditions of the regions were studied before implementing the project and if regular monitoring is being done to ensure the system is functioning properly.

Chikkaballapur farmer Anjaneya Reddy (left) has been appealing to concerned authorities against the project highlighting the possible groundwater contamination due to recharging groundwater with secondary treated wastewater.
Chikkaballapur farmer Anjaneya Reddy (left) has been appealing to concerned authorities against the project, highlighting the possible groundwater contamination due to recharging groundwater with secondary treated wastewater. Photo by Arathi Menon/Mongabay.

All five STPs that supply wastewater to the KC Valley project are operated by Bangalore Water Supply and Sewerage Board (BWSSB) which has set up real-time monitoring of the water quality as per the directions of the Central Pollution Control Board in 2020. Paani analysed this data for seven months, from January to July 2023 every hour, for two crucial wastewater parameters, Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). Their findings indicated that while two of the five STPs, KC Valley-218 and KC Valley-30, didn’t report any data, two others, Kadubeesanahalli-50 and Bellandur Ammani Kere-90 STP, reported only 41% and 21% of the time respectively. The website says that the online data also showed the treated wastewater quality exceeding BOD and COD limits at various times indicating either reporting discrepancies or the STPs’ performance not meeting the required standards or both.

Residents unhappy with wastewater, agriculture affected

With a population of close to four lakhs, a majority of them employed in the agriculture sector, Kolar farmers have the traditional knowledge to decipher that the discoloured water from their water filters, the foul smell from the lake water in the absence of rain, the occasional mass fish deaths being reported in local newspapers, and declining crop production are all indicators of the poor health of water they are forced to accept.

The KC Valley project, of significant magnitude, has not had a long-term study of its potential impact on the environment or health. Delhi-based environment lawyer, Ritwick Dutta, who visited Kolar a year ago, said that since the transfer of water is considered an environmentally benign activity, there is no direct mention of it in the Environment Impact Assessment Notification. But a biodiversity impact assessment is mandatory as per the Biological Diversity Act 2002 which has not been done. “These are water bodies that are being recharged with wastewater. There is a chance of groundwater contamination which cannot be undone. At least three to four years of a thorough investigation into various aspects of potential contamination should have been done before the government implemented this. No prior study that fully rules out potential contamination was done,” he said.

When the concerned departments came under fire for not studying its impact on the environment from the high court in 2020, they set up a review committee to look into the environmental impact of the project. The committee gave a clean chit to the project. Anjaneya Reddy, a resident of Chikkaballapur and a litigant against the project since its inception, challenged the committee’s findings and filed a petition in the court alleging bias against a few members of the review committee. Reddy heads a farmers’ organisation called Shashwatha Neeravari Horata Samithi that has apprehensions regarding the long-term health and environmental impacts of the project.

Chikkaballapur resident Santosh takes his cattle for grazing near Kandavara lake in Chikkaballapur. These lakes filled with secondary treated wastewater from Bengaluru bear signages that warn residents against using the water directly for drinking and agricultural purposes or even washing hands. Photo by Arathi Menon
Resident Santosh takes his cattle for grazing near Kandavara lake in Chikkaballapur district. These lakes filled with secondary treated wastewater from Bengaluru bear signages that warn residents against using the water directly for drinking and agricultural purposes or even washing hands. Photo by Arathi Menon/Mongabay.

Seasonal lakes become perennial and thus, stagnant

Recycling and reuse of water, in industrial and agricultural sectors, is a common practice in India. Bengaluru’s treated wastewater has been filling up city lakes for decades. Cities such as Chennai and Hyderabad too have implemented projects involving treated wastewater. However, using secondary treated wastewater meant for groundwater recharge, finding its way into agricultural lands and drinking water sources with institutional support, is previously unheard of, contends Reddy. “Even the poorest in our cities use soaps, chemicals, surfactants, etc. for cleaning purposes which get mixed with wastewater,” he said. There is also the fear of traces of drugs eliminated through human waste that could find their way into the water. His argument is simple: “Give us good quality drinking water from rivers or water that at least matches the quality of rainwater.”

What is often overlooked in the conversation around the project is the perenniality of the lakes due to the constant supply of water. The water flow in the natural lakes is seasonal with dry periods facilitating desilting and cleaning. Kolar Zilla Parishad CEO Padma Basavanthappa expressed her concerns about the lack of provision for desilting which makes the water stagnant through the year. Rao said that the SAT system has holiday seasons where the lakes are dried on a rotational basis and cleaned which hasn’t been executed here due to unexpected rains in the last few years. He said it will be taken up soon.

If wastewater recharges groundwater, can pollution be far behind?

While the government maintains that the wastewater is meant only for recharging groundwater, the ground realities are somewhat different. Most of the lakes have huge signages at their entrances with instructions that the lake water is only for recharging and utilising it directly for agriculture or drinking or even washing hands is not permitted. However, multiple borewells are seen on the lake beds giving one enough reason to suspect potential borewell contamination.

At Uddappanahalli village in Kolar district we meet farmers Harsha and Balu. Balu who is the water manager (traditionally called neeruganti, watermen in charge of managing water supply) of the village, informed that the lake water seeps into drinking water borewells near them. Harsha alleged the soil is getting degraded due to continuous irrigation using borewell water supplied to them. “The crops are of inferior quality now,” he said. According to Harsha, a fisherman who was given the tender to catch and sell fish there, abandoned it due to poor quality of fish. “Earlier, when you cut open the fish, it used to be white and pink in colour, but now it is black. We can’t eat this fish anymore,” said Harsha. Hemalatha, a 17-year-old commerce student who lives near the lake said the drinking water emits a foul smell even after using a filter.

Kolar farmer Harsha (left) and waterman Balu say that the drinking water is contaminated affecting the soil and fish health. Photo by Arathi Menon
Kolar farmer Harsha (left) and waterman Balu allege that the drinking water is contaminated, affecting the soil and fish health. Photo by Arathi Menon/Mongabay.

Yellamma, a daily wage labourer from Raichur who works at a park near Kandavara lake in Chikkaballapur does not buy the fish from the lake or drink the borewell water. There are multiple water ATMs in both districts that provide reverse osmosis (RO) water at Rs 5 per 20 litres. Groundwater in this region has a history of fluoride and uranium contamination and the water ATMs were established to provide safe drinking water to the villagers. For Yellamma who earns Rs. 450 as daily wage, buying drinking water isn’t always practical.

Dutta said that those involved in the conception and implementation of the project suffer from a classic case of not-in-my-backyard syndrome. The idea of sending urban wastewater to rural areas for groundwater recharge is ethically and practically flawed. “There shouldn’t have been any compromise on tertiary treatment of water if it had to be supplied to rural areas. Even with tertiary treatment, a long-term study to understand the potential impact couldn’t have been compromised,” he said. Gowda of Paani fears that KC Valley project, hailed as a shining example of India’s ingenuity, is slowly turning parched Kolar into a polluted one.


Banner image: A drone shot of water hyacinth-infested Kolaramma lake in the Kolar district of Karnataka. The Karnataka government’s KC Valley project fills lakes or tanks in the water-stressed region of Kolar with secondary treated wastewater from Bengaluru to recharge groundwater. Photo from Anjaneya Reddy.


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