Assam Green Activist Raises Red Flag Over Refinery Effluents in Dhansiri River: An Assam-based environmentalist has sounded the alarm over potential ecological threats stemming from alleged hazardous effluent discharge by Numaligarh Refinery Limited (NRL) into the Dhansiri River in Golaghat district. In a formal complaint submitted to the Central Pollution Control Board (CPCB), the activist warned that the discharge poses a serious risk to the river’s delicate ecosystem, which supports diverse aquatic life and sustains local communities. The concern highlights growing apprehensions about industrial pollution in ecologically sensitive regions of Assam.
Numaligarh Refinery Limited (NRL)’s reported hazardous effluent discharge into the Dhansiri River in Golaghat district has alarmed an Assam environmentalist. The activist informed the Central Pollution Control Board (CPCB) that the discharge threatens the river’s sensitive environment, which supports diverse aquatic species and local residents. Concerns about industrial contamination in ecologically vulnerable Assam are mounting.
Effluent Standards Violated
In his letter to the Member Secretary of the Central Pollution Control Board (CPCB), environmentalist Apurba Ballav Goswami referenced a scientific report prepared by AGT Biosciences (OPC) Private Limited. The report is based on the analysis of a water sample collected from the effluent treatment plant of Numaligarh Refinery Limited (NRL) on March 11, 2025. According to Goswami, the findings suggest potential violations of CPCB’s effluent discharge norms, raising red flags about the refinery’s environmental compliance and its impact on the surrounding ecosystem.
Environmentalist Apurba Ballav Goswami used an AGT Biosciences (OPC) Private Limited scientific report in his letter to the CPCB Member Secretary. On March 11, 2025, Numaligarh Refinery Limited (NRL) collected a water sample for analysis at its effluent treatment plant. The findings show CPCB effluent discharge standard violations, raising concerns about the refinery’s environmental compliance and impact on the ecosystem, according to Goswami.
BOD, COD, Oil Levels Exceeded
According to the letter submitted by Apurba Ballav Goswami, the laboratory analysis revealed that the effluent sample collected from Numaligarh Refinery Limited (NRL) exceeded the Central Pollution Control Board (CPCB)‘s permissible discharge limits set under the Environment (Protection) Rules, 1986. The Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and oil and grease content in the sample were all found to be higher than the prescribed standards for petroleum refineries. These violations, the letter warned, pose serious risks to aquatic life and threaten the long-term ecological health of the Dhansiri river, a vital water body in Assam’s Golaghat district.
Apurba Ballav Goswami’s letter stated that Numaligarh Refinery Limited (NRL)’s effluent sample exceeded the Central Pollution Control Board (CPCB)’s Environment (Protection) Rules, 1986 discharge limits from laboratory analysis. BOD, COD, and oil and grease concentration in the sample exceeded petroleum refinery limits. According to the letter, these transgressions endanger aquatic life and the long-term ecological health of Assam’s Golaghat district’s Dhansiri river.
River Biodiversity at Risk
| Parameter | Test Result | CPCB Permissible Limit | Exceedance |
| Biochemical Oxygen Demand (BOD) | 18.0 mg/L | 15.0 mg/L | Yes |
| Chemical Oxygen Demand (COD) | 142.0 mg/L | 125.0 mg/L | Yes |
| Oil and Grease Content | 11.5 mg/L | 10.0 mg/L | Yes |
Environmentalism activist Apurba Ballav Goswami found alarming levels of contaminants in Numaligarh Refinery wastewater. BOD was 18.0 mg/L, COD was 142.0 mg/L, and oil and grease content was 11.5 mg/L, all surpassing the Central Pollution Control Board (CPCB) regulations of 15.0 mg/L, 125.0 mg/L, and 10.0 mg/L. High levels of pollution in the Dhansiri River might deplete oxygen, kill fish, and destroy the river’s ecosystem and communities.
Toxic Danger to Aquatic Life
Fish species such as mahseer and catfish, commonly found in the Dhansiri River, require dissolved oxygen levels above 4–6 mg/L to survive. However, environmentalist Apurba Ballav Goswami warned that elevated Biochemical Oxygen Demand (BOD) in the river, coupled with a high Chemical Oxygen Demand (COD) of 142.0 mg/L, indicates the presence of a toxic mix of oxidisable pollutants from industrial discharge. This not only reduces oxygen availability but also risks creating hypoxic zones that can lead to fish mortality, suffocation of benthic organisms, and a collapse of the aquatic food chain. He further added that the oil and grease content, measured at 11.5 mg/L, forms a surface film on the water, which blocks oxygen exchange, coats fish gills, and smothers aquatic plants, compounding the ecological damage.
Mahseer and catfish in the Dhansiri River need dissolved oxygen over 4–6 mg/L to survive. However, environmentalist Apurba Ballav Goswami warned that the river’s high BOD and COD of 142.0 mg/L indicate a dangerous mix of oxidisable contaminants from industrial discharge. This reduces oxygen availability and risks hypoxic zones that can kill fish, suffocate benthic creatures, and collapse the aquatic food chain. He stated that the 11.5 mg/L oil and grease concentration generates a surface layer on the water that limits oxygen exchange, covers fish gills, and suffocates aquatic vegetation, compounding ecological damage.
NRL Discharge Dispute
Environmental activist Apurba Ballav Goswami has urged the Central Pollution Control Board (CPCB) to initiate a comprehensive investigation into Numaligarh Refinery Limited’s (NRL) effluent treatment systems and assess the cumulative environmental impact on the Dhansiri River. He emphasized the need for long-term monitoring of water quality and aquatic life, citing repeated violations of discharge norms. In response, NRL strongly denied discharging any untreated effluents into the Dhansiri, clarifying that all generated effluents are treated within the refinery and recycled. The company stated that only stormwater, monitored for compliance, is occasionally discharged—not into the Dhansiri River, but into the Kalioni River, located approximately 6 km away.
The Central Pollution Control Board (CPCB) should investigate Numaligarh Refinery Limited (NRL) wastewater treatment facilities and their cumulative environmental impact on the Dhansiri River, according to environmental activist Apurba Ballav Goswami. He stressed the need for long-term water quality and aquatic life monitoring due to frequent discharge violations. NRL denied releasing untreated effluents into the Dhansiri, saying all effluents are treated and repurposed at the refinery. The company said only stormwater, checked for compliance, is occasionally released into the 6 km-away Kalioni River.
FAQ’s
Who raised the concern about pollution in the Dhansiri River?
The concern was raised by Assam-based environmentalist Apurba Ballav Goswami, who submitted a formal letter to the Central Pollution Control Board (CPCB).
How credible is the testing agency?
AGT Biosciences is a registered private entity known for conducting environmental analysis. However, further verification by CPCB or state pollution boards may be required for regulatory action.
Which regulations are allegedly being violated?
The findings suggest a breach of CPCB norms set under the Environment (Protection) Rules, 1986, and subsequent guidelines for petroleum refinery effluents.
Why is high BOD a concern for rivers?
High BOD means more oxygen is being consumed by microorganisms to break down organic matter. This reduces dissolved oxygen, leading to stress or death in aquatic species, especially fish.
Which fish species are at risk in the Dhansiri River?
Species like mahseer and catfish, which are common in the Dhansiri, are at risk. These fish need oxygen levels above 4–6 mg/L to survive.
What is the main concern raised by the activist?
Goswami cited reports showing excess levels of pollutants such as BOD, COD, and oil & grease in the river, suggesting potential violations of CPCB norms. He called for long-term monitoring of water quality and biodiversity in the Dhansiri River.
