Incident

Alleged discharge of hazardous effluents from Numaligarh Refinery Limited into Dhansiri River in Golaghat, Assam.

Complaint by

Apurba Ballav Goswami an Assam-based environmentalist.

Reported To

Central Pollution Control Board citing violations of CPCB norms under Environment (Protection) Rules, 1986.

Analyzing Agency

AGT Biosciences (OPC) Private Limited.

Date of Sample Collection

March 11, 2025

BOD Level

18.0 mg/L (Permissible limit: 15.0 mg/L) Indicates high organic load causing oxygen depletion in water.

COD Level

142.0 mg/L (Permissible limit: 125.0 mg/L) Suggests high load of oxidisable pollutants.

Oil & Grease

11.5 mg/L (Permissible limit: 10.0 mg/L) Can block oxygen exchange & smother aquatic life.

Ecological Risk

Threat to fish species like mahseer & catfish, possible creation of hypoxic zones, damage to benthic fauna.

Broader Impacts

Bioaccumulation, reproductive failure & long-term food web disruptions across aquatic & terrestrial predators.

Demands by Activist

Independent investigation, long-term biodiversity & water quality monitoring & strict enforcement of environmental norms.

Main River of

Golaghat District (Assam) & Dimapur District (Nagaland)

State(s)

Assam & Nagaland

Length

Approximately 352 km

Catchment Area

~1,220 sq.km

Type

Perennial river

Origin

Laisang Peak, near Intanki National Park, Nagaland

Initial Flow Direction

Northwesterly for 40 km from source

Next Flow Direction

Turns northeast for approx. 76 km up to Dimapur

Final Flow Direction

Turns northward beyond Dimapur till Golaghat; then northwest to join Brahmaputra

Confluence

Joins Brahmaputra River at Dhansirimukh in Assam

Major Tributaries

Doyang River (right bank), Chathe River

Key Locations Along Course

Intanki National Park, Dhansiri Reserved Forest, Dimapur, Golaghat

Districts Traversed

Dimapur (Nagaland), Karbi Anglong (Assam), Golaghat (Assam)

Terrain & Topography

Flows through hills, forests, floodplains & agricultural zones

Eco-sensitive Zones

Flanked by Intanki National Park (Nagaland) & Dhansiri Reserved Forest (Assam)

Ecological Importance

Rich biodiversity with species like mahseer, catfish, otters, kingfishers; home to riparian flora like reeds & bamboo

Human Uses

Drinking water, irrigation, inland fishing, traditional livelihood

Cultural Significance

Revered by local tribal communities; forms part of socio-ecological landscape

Environmental Concerns

Sand mining
Encroachments
Urban industrial pollution
Oil refinery effluent (NRL case in 2025)

Recent Environmental Issue (2025)

Alleged discharge of hazardous effluents from Numaligarh Refinery Limited, exceeding CPCB norms (BOD, COD, Oil & Grease), threatening aquatic life & river ecology

Strategic Significance

Tributary of Brahmaputra; critical to Northeast India’s hydrology & biodiversity

Environment (Protection) Act

1986

Ministry of Environment, Forest & Climate Change (MoEFCC)

Umbrella legislation
Empowers Central Government to take all necessary actions for protecting environment
Enables standards for effluent discharge

CPCB’s effluent standards are issued under this Act

Water (Prevention & Control of Pollution) Act

1974

Central Pollution Control Board (CPCB), State Pollution Control Boards (SPCBs)

Regulates discharge of pollutants into water bodies
Establishes Water Quality Standards
Consent is mandatory for industries to discharge waste into water

NRL requires consent to operate & discharge effluents under this Act

Air (Prevention & Control of Pollution) Act (indirectly linked via ETP emissions)

1981

CPCB & SPCBs

Controls emissions from industrial operations, including gaseous emissions from ETPs (indirect impact on water through atmospheric deposition)

Not directly applicable to Dhansiri but relevant to integrated pollution control

EIA Notification (under EPA, 1986)

First issued 1994, most recent in 2006

MoEFCC

Mandates Environmental Impact Assessment for refineries
Requires Environmental Clearance (EC) for new/refurbished projects
Public hearing & scrutiny of environmental risks

Any expansion or modification in NRL operations should comply with this

National Green Tribunal (NGT) Act

2010

National Green Tribunal

Provides a mechanism for expeditious disposal of environmental cases
Penal provisions for environmental damages
Public access to file grievances

Concerned citizens like environmentalist in Assam can move NGT

Factories Act (Section 41B & C)

1948 (amended)

Ministry of Labour & Employment

Requires hazardous industries to have on-site emergency plans; safe handling & disposal of wastes

Safety, emergency preparedness at industrial sites like NRL

CPCB Norms for Petroleum Refineries (Effluent Discharge Standards)

Under EPA, 1986

CPCB

Specific limits for BOD (15 mg/L), COD (125 mg/L) & Oil & Grease (10 mg/L) for refineries

Violated in Dhansiri case: BOD (18), COD (142), O&G (11.5)

Biological Diversity Act

2002

National Biodiversity Authority

Protection of biological resources, endangered species & riverine biodiversity

Fish like mahseer, endangered aquatic species threatened by hypoxia & toxicity

Wildlife Protection Act (applicable if protected areas like Intanki NP or Dhansiri RF are impacted)

1972

MoEFCC, Forest Department

Prohibits pollution or destruction in protected areas

Important if effluent affects ecosystems adjacent to PAs

PRACTICE QUESTION

Q. Which of following laws in India provides legal basis for setting industrial effluent discharge standards for petroleum refineries?

a) Water (Prevention & Control of Pollution) Act, 1974
b) Environment (Protection) Act, 1986
c) Biological Diversity Act, 2002
d) National Green Tribunal Act, 2010

Answer: (b)

Explanation:
Environment (Protection) Act, 1986 is umbrella legislation under which Central Pollution Control Board (CPCB) sets detailed environmental quality & emission/effluent standards for industries including petroleum refineries. Though Water Act (1974) regulates water pollution & requires industrial consent to discharge, specific standards like BOD, COD & oil & grease limits are issued under EPA, 1986.