HYDERABAD: Crores of public money have been spent on sewage treatment plants (STPs) across Hyderabad to revive its fast-degrading lakes. Yet the latest pollution data shows the strategy has failed to halt the decline, with untreated and partially treated sewage continuing to flow into several waterbodies, raising questions about how STPs are planned, designed, operated and monitored.
Data released by the Telangana Pollution Control Board (TGPCB) shows lake water quality across the Hyderabad Metropolitan Area remains critically poor. Of the 185 lakes, at least 23 have dried up completely, while dissolved oxygen (DO) levels in 25 lakes have fallen below 1 milligram per litre — a level at which aquatic life cannot survive. WHO guidelines recommend DO levels of 5–6 mg/l to sustain healthy ecosystems.
Key indicators such as DO, biochemical oxygen demand and heavy metal concentrations point to persistent sewage inflows despite the presence of STPs. In Mir Alam Tank, Kotha Cheruvu in Alwal, Pedda Cheruvu in Khajaguda, Kamuni Cheruvu and Banjara Cheruvu, oxygen levels have dropped far below acceptable limits. Even Hussainsagar and Durgam Cheruvu, often projected as showcase urban lakes, record DO levels of just 1.1 to 2.7 mg/l.
Recent lake rejuvenation projects linked to nearby STPs have also failed to yield improvements. Bathukamma Kunta in Amberpet, restored by HYDRAA in October 2025, recorded a DO level of 0.6 mg/l in September, which fell further to 0.3 mg/l in October, TGPCB data shows.
Environmentalists say the issue lies not in the number of STPs, but in the flawed model behind them. Donthi Narasimha Reddy, environmentalist and policy expert, told TNIE that sewage management continues to be treated as an afterthought in urban planning.
“When permissions are granted for buildings and layouts, sewage systems should be planned and implemented simultaneously. Instead, due to a lack of space, STPs are constructed inside or along lakes. With no proper sewage disposal system in place, wastewater is diverted into lakes, leading to pollution,” he said.
Narasimha Reddy pointed out that many STPs are designed without factoring in future population growth and rising sewage generation. “Land should be earmarked for STPs in advance. Area-specific sewage plans must be mandatory at the stage of granting construction permits,” he said.
Operational constraints further limit STP effectiveness. Most plants in Hyderabad are designed with fixed capacities of 10–15 million litres per day (MLD). During monsoons, stormwater mixes with sewage, pushing inflows beyond capacity and forcing operators to bypass treatment. In dry months, inflows often fall below minimum operating levels, leading to shutdowns. “As a result, STPs function efficiently only for limited periods, while untreated sewage enters lakes for the rest of the year,” said environmentalist Madhulika Choudhary.
“Lake protection cannot be done by one agency in isolation. Sewage diversion, stormwater management and enforcement involve multiple departments. If agencies work in silos or publicly blame one another, the system will fail,” she said.
Choudhary pointed out that creating new authorities without clear roles and accountability had only compounded confusion. “Taxpayers end up funding multiple agencies that pass responsibility instead of delivering results,” she added.
She also criticised capacity planning. “Plants are designed on current sewage estimates without factoring in growth. A lake receiving 40 MLD of mixed sewage and stormwater may get an STP designed for just 15 MLD. Within a few years, the capacity becomes grossly inadequate,” she said.
Maintenance failures worsen these structural flaws. In several areas, pipelines feeding STPs are clogged with plastic waste, construction debris and sludge, preventing sewage from reaching treatment plants.
HYDRAA officials acknowledge that STPs alone cannot revive lakes unless sewage diversion works are end-to-end. “Even where diversion channels exist, they are often ineffective. In many locations, untreated sewage still flows into lakes. In some cases, STPs themselves are not functioning optimally,” a senior HYDRAA official told TNIE.
The agency has also flagged instances where sewage diverted from one lake is discharged into another, merely shifting pollution. Proposals are under consideration to install real-time sensors at STP outlets and key inflow points to monitor water quality and trigger inspections. However, incomplete separation of stormwater and sewage continues to overwhelm treatment systems during heavy rainfall.
“Technically, we call them lakes, but in reality, many have turned into sewage bodies,” the official added. “Diversion alone is not a solution. STPs must be established where required and, more importantly, must function consistently. The infrastructure exists in many places; the issue is ensuring it works as intended,” he said, acknowledging DO readings as low as 0.3 mg/l in some restored lakes.
Meanwhile, the HMWSSB maintains that lake-centric STPs are a recent intervention. Managing director K Ashok Reddy said that until recently, nearly 90% of the city’s STPs were located along the Musi river. “Very few plants were built near lakes. We have now begun constructing 39 new STPs near lakes under schemes such as AMRUT. Once completed, lake water quality will improve,” he told TNIE, adding that the work would take about a year.
Ashok said all operational STPs are linked to online monitoring systems and inspected by the PCB. “At present, 45 STPs are functional, and the remaining units will be integrated shortly,” he said. On capacity planning, he said the Water Board follows a master plan that accounts for sewage generation, future population projections and area-specific needs. He acknowledged that stormwater and sewage still mix in parts of the city. “Around 80% of Hyderabad has separate networks, but some areas still use common lines. GHMC is implementing a stormwater master plan to address this,” he said.
PCB officials concede that while lakes are not meant to hold potable-quality water, persistently low oxygen levels point to excessive organic loading and failure of sewage management systems.
Lakes below DO levels of 1 mg/l
Bathakamma Kunta (Amberpet) - 1 STP (339 MLD)
Langar Houz lake - 1 STP (1.25 MLD)
Mir Alam tank - 3 STPs (41.5 MLD, 5 MLD, 10 MLD)
Pedda Cheruvu (Khajaguda) - 1 STP (7 MLD)
Nalla Cheruvu, Uppal - 1 STP (86.5 MLD)
Safilguda lake - 1 STP (0.6 MLD)
Dissolved oxygen levels of Durgam Cheruvu: 2.7 mg/l, 2 STPs
Dissolved oxygen levels of Hussainsagar: 1.1 mg/l
Hussainsagar has three STPs. In 2022, HMDA initiated tenders to upgrade these three STPs to double their capacities (5 - > 10 MLD, 20 - > 40 MLD, 30 - > 60 MLD).
