Lok Sabha Question No. 1299 (UNSTARRED), answered on 2025-12-08
Subject: Pollution in Thenpennai River
Ministry: ENVIRONMENT, FOREST AND CLIMATE CHANGE
Asked by: Thiru Dayanidhi Maran, Thiru Dr. S Jagathratchakan

## GOVERNMENT OF INDIA

## MINISTRY OF ENVIRONMENT, FOREST AND CLIMATE CHANGE

## LOK SABHA UNSTARRED QUESTION NO. 1299

TO BE ANSWERED ON 08.12.2025

## Pollution in Thenpennai River

## 1299. THIRU DAYANIDHI MARAN: SHRI S JAGATHRATCHAKAN:

Will the Minister of ENVIRONMENT, FOREST AND CLIMATE CHANGE be pleased to state:

- (a) whether the Government is aware of untreated sewage discharge from Karnataka into the Thenpennai river, and the estimated volume of sewage entering in to the river on a daily basis;
- (b) the  official  estimate  of  daily  volume  entering  Tamil  Nadu  along  with  the  assessed impact on downstream districts-Krishnagiri, Dharmapuri, Thiruvannamalai, Villupuram and Cuddalore- including incidents of toxic foam, water contamination and public-health risks;
- (c) the status of compliance by Karnataka and the Central Government with the National Green Tribunal (NGT's) directions on preventing sewage discharge into the Thenpennai, including dates of action-taken reports submitted.
- (d) whether the Government has conducted or reviewed water-quality testing at inter-State entry points and downstream reservoirs, and if so, the details and the current status thereof; and
- (e) the remedial and enforcement measures taken under the National River Conservation Plan to prevent further contamination and safeguard drinking water, agriculture and ecosystems in Tamil Nadu?

## ANSWER

## MINISTER OF STATE  IN THE  MINISTRY OF  ENVIRONMENT, FOREST AND CLIMATE CHANGE (SHRI KIRTI VARDHAN SINGH)

(a) to (e) To  monitor  the  pollution  of  water  bodies  in  the  country,  Central  Pollution Control  Board  (CPCB)  in  association  with  State  Pollution  Control  Boards  (SPCBs)  and Pollution Control Committees (PCCs) has established a Water Quality Monitoring Network under the National Water Quality Monitoring Programme (NWMP). Currently, water quality monitoring is carried out at 4922 locations in the country.  It is the primary responsibility of States/Union Territories (UTs) and Urban Local Bodies to ensure required treatment of sewage and industrial effluents  to the prescribed  norms before discharging into the rivers and other water bodies. The Central Government has laid down standards for the quality of treated sewage and treated industrial effluent to be discharged into rivers and these standards are enforced by State Pollution Control Boards/Pollution Control Committees (SPCBs/PCCs).

As per the information provided by Karnataka State Pollution Control Board (KSPCB), the total estimated quantity of sewage generated in the Thenpennai river catchment area is 1329 MLD. Presently, Bengaluru Water Supply and Sewerage Board (BWSSB) is having 26 STP's with installed capacity of  958.5 MLD & is treating 830 MLD sewage and 12 STP's are reported to be under proposal.

Further, It is reported by KSPCB that KSPCB is monitoring the river water quality at Mugalur bridge once in a month regularly apart from various locations along river Thenpennai. As per the analysis report of river Thenpennai submitted by KSPCB, the river water quality meets the criteria  'E'  (Irrigation,  Industrial  Cooling,  Controlled  waste  disposal)  category,  as  per  the Designated Best Use Water Quality Classification set by the Central Pollution Control Board (CPCB).

Hon'ble National Green Tribunal (NGT) vide order dated 18.12.2024 in Original Application No. 1374/2024 (Principal Bench) while hearing the issue of Toxic Foam in Tamil Nadu's Hosur after Dam Discharges Surplus Water, on suo-moto basis,  directed all the respondents to file their responses before the appropriate bench of the Hon'ble Tribunal and transferred the case to Hon'ble NGT Southern Zone, Chennai. Subsequently, the case was re-numbered as O.A No. 14 of 2025 (Southern Zone).

In compliance of the Hon'ble NGT's order dated 18.12.2024, CPCB submitted  report dated 01.04.2025, in which, while referring about the  report prepared for  'Polluted River Stretches for Restoration of Water Quality - 2022'  for identification of polluted river stretches in the country, it is stated that  the "Dakshina Pinakini along Mugaluru" stretch is identified as one of the  Polluted  River  Stretch  (PRS)  along  Mugaluru  under  Priority  I,  as  the  maximum  BOD observed as 111 mg/L during the period 2019 & 2021. The location is downstream of Bengaluru city in Karnataka.

CPCB - Regional Directorate, Bengaluru monitors water quality at Karnataka-Tamilnadu interstate  location  at  river  'Thenpennaiyar'  at  Chokkarasanapalli  Bridge  under  National  Water Quality Monitoring Programme  (NWMP)  on  quarterly  basis.  The  location is further downstream of Bengaluru city in Karnataka

The officials of CPCB, Regional Directorate, Bengaluru along with officials of  Karnataka State Pollution Control Board and  Tamil Nadu State Pollution Control Board (TNPCB) carried out sampling of six locations at River Thenpennai, namely, Channasandra bridge (01), Mugaluru bridge (01) in Karnataka State, Chokkarasanapalli (01), Kelavarapalli dam (dam water/upstream, downfall near gate/downstream, Mitteganahalli bridge/ Marasandra) (03) in Tamil Nadu State on 28.10.2024. . The assessment  of water quality data for the  year 2024 indicates that Dissolved Oxygen (DO) is observed as BDL (less than 0.3 mg/L), pH in the range of 7.24 - 8.1, Bio-chemical Oxygen Demand (BOD) in the range of 17 - 52.4 mg/L and Fecal Coliform in the range of 2,80,000 - 79,00,000 MPN/100 ml.

Further, as per the information provided by KPCB, pursuant to the directions of the Hon'ble NGT in O.A No. 111/2020, the Chief Secretary to the Government of Karnataka has filed action taken/compliance reports  dated.  01.04.2025,  20.08.2025  and  13.11.2025 before  the  Hon'ble NGT, Chennai Bench.

As per input provided by TNPCB,   The Thenpennai River stretch is not covered under the National River Conservation Plan (NCRP). However, as per NGT (SZ) order dated 20.07.2020, regular water-quality monitoring at the Tamil Nadu entry point is carried out under National Water Quality Monitoring Programme. Further Government of TamilNadu reported that they have installed Real Time Water Quality Monitoring station at Thenpennai River for real time monitoring  of  the  river  water.  TNPCB  coordinates  with  CPCB  and  upstream  agencies  for regulatory compliance and improvement of river water quality.

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