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TN's Cooum river 80% dirtier than sewage
20 Aug 2008, 0441 hrs IST, Ajitha Karthikeyan,TNN
CHENNAI: It s known to be the city s smelly eyesore, so it should hardly come as a surprise that the Cooum river is a killer water body with high toxic content. But a recent study by the Tamil Nadu fisheries department shows that the river, when flowing within city limits, has more toxins than even a sewer.
The value of biological oxygen demand (BOD) which determines how fast biological organisms use up oxygen in a water body is usually taken as a measure of how clean a river is. Clean rivers have a BOD of below 1 milligram per litre (mg/L), moderately polluted rivers have a BOD value in the range of 2 to 6 mg/L. Municipal sewage, if efficiently treated by a three-stage process, should have a value of about 20 mg/L or less. Cooum's BOD value near Napier Bridge is 36 mg/L. That would make the river the citys biggest sewer and 80% more polluted than treated sewage. |