Why India Needs To Urgently Rehaul Sewage Treatment Plans

The result?

More than half of the rivers in India are highly polluted, and many others are at levels considered unsafe by modern standards. In a study in 2018, the Central Pollution Control Board (CPCB) found that about 13% of 351 river stretches on 323 rivers were severely polluted and 17% were moderately polluted. And it is the disposal of domestic sewage from cities and towns that is the biggest source of pollution of water bodies in India, the CBCB has found.

According to the World Bank, 21% of communicable diseases are linked to unsafe water with contaminated water a major contributor to diarrhoea, opportunistic infections, and malnutrition, globally leading to around 1.7 million deaths each year. Over 90% of these fatalities occur in developing nations, with nearly half being children.

Sewage in India is a growing problem. According to the Center for Science and Environment (CSE), wastewater generation will increase by about 75–80% (54-58,000 MLD) by 2050. That would result in a figure that is approximately 3.5 times the country's existing installed treatment capacity, highlighting an urgent need to significantly scale up wastewater treatment infrastructure, the CSE report says.

Experts say India needs a better system of sewage treatment that is decentralised, nature-based, and more suited for filtering pollutants that are common in India.

Water pollution in India

The 2018 CPCB study monitored river water quality using Biochemical Oxygen Demand (BOD) as an indicator of pollution. Apart from high BOD, they found high levels of Chemical Oxygen Demand (COD), heavy metals, arsenic, fluorides and hazardous chemicals in many places, especially in the groundwater in these regions.

Even the Ganga, considered holy in India--and where many take a dip--is in a dire state, with mounds of rubbish strewn along the riverbanks and in the water. According to the CPCB, in the first week (January 12-20) of the 2025 Kumbh Mela--a religious gathering--at Prayagraj, the level of faecal coliform varied between under 1.8 and 49,000 MPN, the most probable number, per 100 ml for the Ganga; and between 2,000 MPN and 33,000 MPN, per 100 ml for the Yamuna. According to the norms of the Ministry of Environment, Forest and Climate Change (MoEFCC), this often exceeded the maximum permissible limit for bathing water of 2,500 MPN per 100 ml and the desirable level of 500 MPN per 100 ml.

As per third party inspection in 2019, 71% of towns along the Ganga were directly disposing their waste into the river, because they lacked proper municipal waste plants.

South Asia produces just about 7% of global wastewater despite a population share of 24%, whereas the 5% of people living in North America account for 20% of global wastewater production, as per these 2021 estimates of wastewater produced globally.

Yet, India accounts for 17% of the world’s scattered municipal waste, while “70% of potential leakage of municipal solid waste into aquatic environments occurs in China, South Asia, Africa, and India”, Adriana Gomez Sanabria and Florian Lindl of the Pollution Management Research Group in Austria estimated in a 2024 study published in the journal Nature.

Access to safe water can improve with better wastewater management

India has 1,486 cubic metres (m3) of annual per capita freshwater availability, making it ‘water stressed’, a Ministry of Jal Shakti press release in 2024 said. A country is classified as ‘water stressed’ when its annual per-capita water availability is below 1,700 m3 per capita per year, and as ‘water scarce’ when the availability is below 1,000 m3 per capita per year. However, the water availability in many regions of the country may vary due to high temporal and spatial variation of precipitation, another government press release from 2020 noted.

There are 163 million Indians who lack access to safe drinking water, especially in urban areas where water resources are under significant pressure due to increasing demand.

The average water supply in urban local bodies in India is 69.25 litres per capita per day (LPCD) against the benchmark of 135 LPCD, as per Central Public Health and Environmental Engineering Organisation.

Water pollution worsens India’s water crisis by contaminating available sources, making them unsafe for consumption.

India’s rivers receive about 100 times more sewage per capita from urban than rural populations. Treating this wastewater could help India mitigate water stress, IndiaSpend had reported in April 2025.

But southern Asia has the lowest rates of used water collection, treatment and reuse globally.

For instance, even as 24 out of 34 districts experience water shortage in Maharashtra, only 4% of wastewater in Maharashtra is reused. This is contrary to the State Water Policy (2019) which says that “a minimum of 30% of recycled water should be reused to reduce freshwater demand within five years”.

And this is not limited to Maharashtra, According to NITI Aayog, less than 1,000 MLD of treated wastewater is currently being reused in India. This accounts for just 3% of the total treated wastewater and only about 1% of the total wastewater generated in the country.

India’s efforts at sewage treatment

According to Swachh Bharat Mission (SBM) 2.0 guidelines from 2021, Indian cities with less than 100,000 population require 13,000 MLD of STP capacity for which SBM budgeted Rs 79,983 crore ($9.3 billion) between October 2021 and October 2026. This includes construction of STPs, interceptor and diversion drains and procurement of desludging vehicles.

Source: SBM 2.0 operational Guidelines, 2021

Cities with a population of over 100,000 are covered under the AMRUT 2.0 mission, launched in 2021 for building sewerage and septage management projects and water conservation reforms. The aim is to recycle treated wastewater to meet 20% of the total urban water demand and 40% of industrial water demand at the state level. The budget for this programme is nearly Rs 3 lakh crore which includes a Union government share of Rs 76,760 crore. Of this, Rs 27,600 crore has been earmarked for sewerage and septage management projects for five years.

Under AMRUT 2.0, 592 sewage/septage projects have been approved so far, for 6,739 MLD sewage treatment capacity. Of this, 2,093 MLD capacity is for recycle/reuse. We have asked the Ministry of Housing and Urban Affairs about the current status of these projects, and will update the story when we receive a response.

The Union budget allocated Maharashtra, which has the country’s largest urban population, Rs 9,310 crore under AMRUT 2.0. In September 2022, the National Green Tribunal (NGT) reportedly imposed fines amounting to Rs 12,000 crore on Maharashtra for not managing solid as well as liquid waste, and thus causing harm to the environment. According to the report submitted by the Maharashtra Pollution Control Board to the NGT, Rs 7,040.71 crore was allocated for used water management projects as of September 2022. However, between August 2022 and June 2024, sewage treatment capacity increased by only 545 MLD, while sewage generation rose by 788 MLD. Of 414 urban local bodies, only 41 cities had STPs as of January 2024, while 270 have upcoming STPs.

In Mumbai, the failure to adequately treat wastewater and prevent leakages is evident not only in the severe pollution of all four of its rivers, but also in the city’s growing dependence on ecologically damaging supply-side solutions, said Rishi Aggrawal, a Mumbai-based environmentalist and founder of Mumbai Sustainability Center (that runs Safai Bank of India for waste management). One such example is the proposed Gargai dam--a greenfield water storage project that will require the destruction of a pristine forest ecosystem and the felling of nearly half a million trees. “It reflects a systemic failure,” Aggrawal said, pointing out that “instead of fixing existing inefficiencies, we continue to push for projects that come at an enormous ecological cost”.

To support river conservation, the Ministry has been assisting States and Union Territories by offering financial and technical support to reduce pollution in designated river stretches. This is done through the central sector scheme Namami Gange for rivers within the Ganga basin, and the centrally sponsored National River Conservation Plan for other rivers.

Under the Namami Gange Programme, the government has sanctioned 161 sewage management projects at Rs 24,581 crore for creation and rehabilitation of 5,501 MLD sewage treatment capacity and laying 5,134 km of sewerage network. However, by 2022, only about 32% of the total sewage treatment capacity had been created or rehabilitated. The progress on sewer network laying was better with 81% completion.

IndiaSpend has reached out to the National Mission of Clean Ganga and the MoEFCC for the latest data on progress of the mission. We will update this story when we receive a response.

Toxic foam in a polluted river near Pune

Is India’s sewage management strategy working?

Effluents from STPs in India are legally required to meet water quality standards, with the permissible limit for BOD set at 10 mg/L for metro cities & 20 mg/l for other cities. However, the Ministry of Jal Shakti mandates a much stricter BOD level of 3 mg/L or less for water to be considered safe for ‘outdoor bathing’.

As a result, even if an STP discharges water with a BOD of 10 mg/L--well within legal discharge norms--it can still raise the overall BOD of the receiving river, especially during low-flow conditions. This prevents the river water from meeting the required bathing water standards.

If the treated effluent contains excess nutrients or pathogens, it further deteriorates water quality. The situation is exacerbated as many STPs underperform, releasing untreated or partially treated wastewater or bypassing treatment altogether, thereby compounding river pollution.

As per the Performance Evaluation of Sewage Treatment Plants in Ganga Front Towns by CPCB in 2019, Ganga front towns generate 3,558.5 MLD of sewage, but the total installed capacity was 1,956.7 MLD, of which 1,064.2 MLD was utilised, indicating a 45% treatment gap. The CPCB had told the local government in Delhi that disinfecting equipment in STPs needs to be upgraded as, of the Delhi Jal Board’s 38 monitored STPs, only two were complying with the standards of fecal coliform.

Infrastructure for urban sanitation systems is poorly planned and implemented. “In places like Lucknow and Kanpur, large STPs based on Upflow Anaerobic Sequential Batch Reactors technology are unable to recover energy from sewage,” said Depinder Kapur, an independent water, sanitation and hygiene (WASH) consultant based in Delhi. “These systems were marketed as modern solutions, but they’re not suited to India’s context--especially when the sewage is highly diluted with water. To generate energy, you need to hold the wastewater for at least 36 hours. How do you hold hundreds of millions of litres a day in these plants in Lucknow and Kanpur, for that long, from diluted sludge? It’s just not feasible.”

Part of the problem lies in how sewage generation is estimated. The standard assumption is that 80% of supplied water returns as wastewater, but real-world discharge often exceeds projections. A 2016 paper by Raghu Dayal in Economic and Political Weekly cited CPCB data showing actual measured wastewater discharge into the Ganga was 6,087 MLD--123% higher than estimated.

Flawed projections result in poorly planned infrastructure.

“STPs are typically designed for a 25-year horizon assuming gradual increases in sewage flow. This results in oversized infrastructure that lacks adequate sewage load in the present, leading to underutilisation or complete non-functionality,” Kapur said. “New STPs are sometimes built next to older ones, and sewage is diverted from old to new plants temporarily to show they are ‘functioning’ for inauguration. This diversion leads to old plants becoming defunct, increasing maintenance burdens and costs.”

In addition, STPs might not be removing certain contaminants effectively.

For instance, the ability of STPs to remove pharmaceutical contaminants from water is varied, with efficiency ranging from 12.5% to 100%, as per a March 2017 study on pharmaceuticals and personal care products in Indian water bodies.

According to the World Health Organization (WHO), Antimicrobial resistance (AMR) is one of the top global public health threats. Most existing wastewater treatment processes globally are incapable of removing antimicrobial-resistant bacteria. Antibiotic residues have been found in river water samples across India, particularly in four key rivers--the Cooum in Chennai, the Gomti (Lucknow), the Yamuna (New Delhi), and the Zuari (Goa) along with antimicrobial resistance genes in the mass bathing sites of the Ganges.

“In low-income countries like India, where the underprivileged population depends directly on surface water for consumption”, it is even more important to remove such resistant bacteria from the water, said a 2022 study.

“We must realise that if there is a problem in the way our STPs are not able to function as per norms and remove organic load, how will we even reach the level of addressing AMR?” said Kapur. He added that removing pharmaceutical contaminants or resistant bacteria requires advanced treatment technologies. But “even if the government installs an additional AMR treatment system, it won’t work unless the basic sewage treatment functions are first fixed. These kinds of add-ons often become tokenistic without addressing core operational failures”.

Often, STPs remain non-functional because operators are not paid, or the technology installed does not fit the local context, Kapur said.

He highlights a common issue in infrastructure development: the lack of consideration for local feasibility factors like land availability and sewage flow patterns. For instance, he explains that STPs are built and they don’t get sewage from houses because they are not connected to the sewerage system. Households that had septic tanks are expected to change their internal plumbing to accommodate for a sewerage connection, a cost that households are unwilling to bear.

This issue is not limited to rivers--when such effluents flow into lakes, they can similarly degrade water quality, leading to increased nutrient loads, algal blooms, and reduced suitability for recreational or ecological use. For instance, Bengaluru sends its STP-treated waste water to fill its large lakes in the city as well as for agriculture in neighbouring districts, Kapur said.

Way ahead

Solutions must be adopted according to the local topography, weather, land cost, economic value and long-term sustenance.

The nature of urbanisation, its link with rural areas and agriculture, will decide the type of centralised or decentralised sanitation systems possible for a city, said Kapur.

A range of hybrid nature-based systems can be adopted for decentralised sewage treatment--in which an STP serves a set of colonies and the municipal corporation bears the responsibility for running and operating the plant. These are less energy intensive, use mostly organic materials and employ natural filtration approaches. However, their implementation in India is limited. Large dense unplanned settlements need to treat their wastewater locally and reuse the treated wastewater for construction works, for filling reservoirs to provide cooling and recharge of groundwater in their vicinity, Kapur explained.

One example of a wastewater treatment approach comes from Odisha. Odisha implemented a wastewater management model combining a sewage system for large cities and Faecal Sludge & Septage Management for small and medium towns. The state created and operationalised 13 STPs in six bigger cities and 112 faecal sludge treatment plants across all the 115 urban local bodies.

Overall, the journey from pilot approval to state handover took 40 months, including delays caused by Covid-19, says eGov Foundation, whose technology is used in the project. This, along with adoption of low-cost technology and engagement of local community groups in the management of FSTPs, helped improve water quality in 17 out of the total of 19 polluted river stretches to non-polluted between 2017 and 2023, according to the CPCB.

“Nature-based or hybrid solutions--like wetlands, biofilters, or soil-based decentralised treatment--can be effective in theory,” said Kapur. “But their implementation is severely limited in Indian cities due to space constraints, political priorities, and a lack of integrated urban planning.”

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