From Lifeline to Liability: Mahananda River’s Decline Sparks Outcry

Once a vital water source and ecological artery for Siliguri, the Mahananda River is now teetering on the brink of environmental collapse. A recent assessment by the ICAR-Central Inland Fisheries Research Institute (CIFRI), Barrackpore, has sounded the alarm over alarming pollution levels in a 2.1 km stretch near Janta Nagar, exposing the river’s deteriorating health and the looming threat to public safety.

The study reveals that untreated industrial effluents, medical waste, and domestic sewage are being directly discharged into the river. The Biochemical Oxygen Demand (BOD) level has reached 2.4 mg/L, a clear indicator of high organic pollution. Even more concerning is the Total Coliform Count of 280 MPN, far exceeding safe limits and pointing to severe bacterial contamination from faecal matter.

BOD (Biochemical Oxygen Demand) – principle revolves around the amount of dissolved oxygen consumed by microorganisms while breaking down organic matter in a water sample under aerobic conditions. Essentially, it measures the oxygen required for bacteria and other microorganisms to decompose organic material present in water at a specific temperature over a set time. This measurement is crucial for assessing water quality and the impact of pollutants on aquatic ecosystems.

Sources of BOD include leaves and woody debris; dead plants and animals; animal manure; effluents from pulp and paper mills, wastewater treatment plants, feedlots, and food-processing plants; failing septic systems; and urban stormwater runoff.

Typical Scale of BOD Results (result in mg/L):

<1: pristine water; 1 – 2: very good; 3 – 5: moderately clean; 6 – 9: somewhat polluted;

100+: very polluted; 200 – 600: untreated sewage; 1000+: food processing waste.

Total Coliform Count – is a measurement of bacteria, specifically coliforms, found in a water sample. These bacteria are often used as indicators of the general sanitary condition of water and food. While not all coliforms are harmful, their presence suggests the potential for other disease-causing organisms to be present.

Water quality monitoring plays an important role in modern intensive fish farming management. Advancements in new sensor technologies, automated controls, and data telemetry now allow for unprecedented monitoring capabilities to strengthen insights in designing mitigation and management strategies.

Coliform Bacteria in the family Enterobacteriaceae:

Residents living along the riverbanks report that the water, once used for household needs, has become visibly murky and foul-smelling. “We used to rely on this river for daily chores. Now, it’s a health hazard”, said a local resident.

Environmentalists blame unregulated small-scale industries and the absence of sewage treatment infrastructure for the crisis. “This is a textbook case of urban neglect,” said one expert, warning that the upcoming monsoon could spread contaminants downstream, endangering biodiversity and communities alike.

The Siliguri Municipal Corporation has already halted city-wide water supply from the river, distributing packaged drinking water as a temporary measure. However, experts stress that long-term solutions are urgently needed. These include:

• Establishing decentralised sewage treatment plants
• Enforcing strict industrial effluent regulations
• Conducting regular water quality monitoring
• Launching public awareness campaigns on river conservation

Without certain swift and coordinated action, the Mahananda River may soon cross an ecological tipping point — from which recovery could be nearly impossible.