CHENNAI: Two out of three rivers that originate in Karnataka and flow into Tamil Nadu are polluted. More than Cauvery, its tributaries Thenpennaiyar and Arkavathi are highly polluted, carrying loads of Karnataka sewage. This was revealed by the Central Pollution Control Board (CPCB), which filed a joint monitoring report before the Supreme Court on Monday. The report was submitted in connection with a case filed by Tamil Nadu in 2015 to restrain Karnataka from letting untreated sewage and industrial effluents into the rivers.
The report, a copy of which is available with Express, says a joint monitoring was done for nine months from September 2017 to May 2018. Water samples were collected every month from specific locations to ascertain the level of pollution in the rivers when they enter Tamil Nadu from Karnataka. The samples were taken from Ajjibore (river Cauvery), Chokkarasanapalli (river Thenpennaiyar) and the Arkavathi river. Four parameters, including Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), pH and Fecal Coliform (FC) were analysed.
The joint monitoring and analysis of samples revealed that the Cauvery at Ajjibore was meeting the water quality criteria limits for eight months with respect to the indicator of organic pollution measured as BOD, however, exceeding criteria limited in May 2018. The bacteriological pollutant faecal coliform was found to be exceeding limits in October 2017 and May 2018, while Dissolved Oxygen (an indicator of health of the river) was meeting the standards during all the months. Therefore, Cauvery was described as ‘clean’.
However, the Thenpennaiyar and the Arkavathi were found to be polluted. Especially, the Thenpennaiyar is highly polluted as samples revealed high values of BOD, faecal coliform and very low concentration of dissolved oxygen during all the nine months. Arkavathi showed high pollution of BOD in December 2017 and May 2018 and faecal coliform during September, October 2017 and May 2018.
CPCB said the Karnataka government has to review the design standards of sewage treatment plants (STPs) and effluent treatment plants (ETPs) and improve strict standards for treatment of sewage and effluents. The board also said the option of installation of real-time water quality monitoring stations at the inter-state borders of the Cauvery and Thenpennaiyar should be considered by both the States. Besides, Karnataka was asked to prepare a comprehensive plan of action for restoring water quality in the Thenpennaiyar and the Arkavathi.
“Polluted river stretches are identified in both the States. Details of polluted rivers and the cities and towns that discharge wastewater was communicated to Pollution Control Boards. However, for regular follow up action, it may be appropriate to form a committee comprising officials from both the States,” the CPCB recommended.
Findings of CPCB
A joint monitoring was done for 9 months from September 2017 to May 2018
Cauvery’s tributaries, Thenpennaiyar and Arkavathi, carry loads of Karnataka sewage
Samples from Thenpenaiyar revealed high values of BOD, faecal coliform during all the nine months
Arkavathi showed high pollution of BOD in December 2017 and May 2018