Chennai: Buckingham Canal near Napier Bridge the most polluted stretch, finds TNPCB

CHENNAI: It is no secret that the Buckingham Canal running through Chennai has become a sewage stream already. But the most polluted stretch of the British-era canal is at the confluence of the canal with Cooum River and Bay of Bengal, an analysis revealed.

Cooum river is already the most polluted river in the country with Biological Oxygen Demand of more than 340 mg/L.

As per the analysis conducted by the Tamil Nadu Pollution Control Board (TNPCB), several parameters have exceeded in the sample collected from the canal near Napier Bridge. Conductivity, chloride, total dissolved solids (TDS), sulphate and hardness levels were higher in the sample collected near Napier Bridge than the samples collected from other 5 different locations of the canal. Magnesium, BOD (Biological Oxygen Demand), fluoride and iron also exceeded the TNPCB standard for drinking water quality near Napier Bridge.

In other five locations such as opposite to IOCL (Indian Oil Corporation Limited) in Tondiarpet, opposite Chennai Higher Secondary School in Patel Nagar in Kodungaiyur, opposite waste processing center in Navalur, Kannagi Nagar near Captain Cotton Canal and Old Washermen near Otteri Nullah Canal out, parameters such as BOD, fluoride and iron only exceeded the standards. The analysis covered around 9km of the canal from IOCL and Napier Bridge.

A TNPCB report said that apart from IOCL, there is no industrial activity along the 9km stretch of the Buckingham Canal suggesting that the pollution is mainly due to discharge of domestic sewage.

As against the drinking water standards of 500 to 2,000 mg/L of TDS, sample near Napier Bridge had a TDS of 5,560 mg/L. Presence of Chloride and sulphate was recorded as 2,599 mg/L and 555 mg/L respectively against the specifications of 250 to 1000 mg/L and 200 to 400 mg/L. Conductivity level was at 9,810 microsiemens per centimetre.

To put it in perspective, of the six samples collected, the sample in Patel Nagar had a TDS of 1,094 mg/L – second highest after Napier bridge. Sample taken near Navalur had 550 mg/L of chloride and the sample collected at the same spot showed conductivity of 2,060 – also the second highest levels. Hardness level near Napier bridge was 1,200 mg/L against the standard of 200-600 mg/L.

Even as the levels of BOD is the one of the parameters that determine the suitability of any water body for life to thrive, the entire 9km stretch of the Buckingham Canal have BOD levels upto 248 mg/L (at Navalur) as against the standard specification of 3 mg/L.

However, the BOD was relatively lesser near Napier bridge where BOD of 50 mg/L was observed. On the other hand, samples collected near IOCL and Patel Nagar had a BOD of 154 mg/L and 190 mg/L. (BOD) is a measure of how much oxygen is used by microorganisms to break down organic matter in water. High BOD levels can stress, suffocate, and kill aquatic organisms. Chemical oxygen demand (COD) ranged from 144 mg/L to 896 mg/L in the six locations.

However, the TNPCB claims that apart from the disposal of treated sewage from sewage treatment plants at Saidapet, Kotturpuram, Perungudi and Sholinganallur, there is no effluent discharge by industrial activity along the stretches of Buckingham Canal and Adyar river, but TNPCB has not clarified on the source of the higher levels of pollution.

While the Buckingham Canal on the northern side exceeded the parameters, a separate analysis conducted on the 500 m stretch on either side of Chepauk MRTS station also revealed higher levels of pollution. The BOD levels in the stretch were found to be at 72 mg/L.