CHENNAI: The three-month soil remediation trials carried out by Hindustan Unilever Limited (HUL) in the now-defunct thermometer factory at Kodaikanal failed to achieve even the ‘liberal’ 20 mg/kg mercury clean-up standard. Environmentalists suspect that the trials may have liberated more mercury to the environment than was recovered.
While the Union Ministry of Environment, Forests and Climate Change recommends a remediation target level of 6.6 mg/kg, HUL’s alleged failure to meet the 20 mg/kg standard is raising several questions over the quality of soil remediation and retort process being adopted by the company. The trials were conducted between August 16 and November 18. This included soil washing and retorting. Totally, 87 tonnes of soil was processed during the trials.
The findings from soil washing trials reveal that in soils with mercury concentration less than 100 mg/kg only 70% of the total soil meets the 20 mg/kg remediation standard. When mercury concentrations range from 100 mg/kg to 250 mg/kg, the success rate comes down between 50 and 60%.The retorting trials encountered several problems, including “material conveyance issues, thermal expansion and vapour leak.” The data relating to retort trials involving 10 batches of contaminated soil reveal that retorting failed to achieve the 20 mg/kg target in 80 per cent of the batches.
Noted environmentalist Nityanand Jayaraman said a careful analysis of the information provided by HUL and TNPCB reveals that the trial run was not merely a failure, but may have mobilised more mercury into environment than it recovered.“Calculations based on information provided by Unilever and TNPCB reveal that the trial remediation process resulted in zero recovery of mercury and a significant mobilisation of mercury from the soil to the environment, air and water media,” he said.
According to the Stop Work Criteria adopted by HUL, vapour readings above 0.025 mg/m3 trigger high protection respirators, and all work needs to be suspended at levels above 0.05 mg/m3. Air quality data presented by TNPCB finds that air mercury levels in three out of five workspaces inside the factory exceeded the safe workplace mercury vapour levels of 0.05 mg/m3 prescribed in the Factories Act. The Soil Wash Area recorded a reading of 0.1 mg/m3 – two times higher than levels at which work has to be stopped. Jayaraman added that a bulk of the mercury has been transferred from the soil to the water medium, even as the Scientific Experts Committee and TNPCB have focused their attention only on retort.
“Of the total of 2717.12 gm of mercury contained in the combined soil of two batches – SW06 and SW07, less than 20 per cent was concentrated in the fine soil fraction. More than 65 per cent of the mercury – i.e. 1774.38 grams of mercury – was released into water and air. This is nothing but a mini environmental disaster,” he alleged. Despite repeated requests, no data has been presented on the mercury released into the Pambar Shola during the trials.
Kodaikanal resident Navroz Mody, who is also a member of Local Area Environment Committee and the person who exposed illegal dumps of mercury lanced broken thermometer glass in 2000 that laid foundation for the case, said this is a clear case of HUL using substandard remediation process and lobbying for relaxed clean-up standard.
Shweta Narayan, legal researcher and activist, said it is bizarre to see TNPCB and Scientific Experts Committee agreeing to Unilever’s request for permission to submit a plan to upscale soil remediation work despite the total failure of the three month-trial remediation.
HUL denies charge, says trials a success
In an e-mail response to Express, HUL spokesperson said the company has been able to achieve the soil remediation standard of 20 mg/kg as directed by TNPCB and said the argument that 20 mg/kg is a liberal standard was incorrect. “TNPCB and SEC with the help of leading scientific experts have arrived at the standard of 20 mg/kg. The clean-up process followed by HUL is based on best practices adopted globally. Available technologies have been evaluated by NEERI and soil washing and retorting were adopted as the best option for the site. For the soil remediation trials, a pilot soil washing and retort plant was set up and used during the three month trial period. The remediation equipment met the remediation trial objectives.
25 batches of soil were washed and sieved through six grades. Soil washing as a means to concentrate mercury in the fine fraction of soil was a failure. Bulk of the mercury transferred to the water medium trigger concerns about release into Pambar Shola.
- Remediation target levels of 20 mg/kg attained only 50 to 70% of times when feed concentration was less than 100 mg/kg, and not at all if it exceeded 100 mg/kg
- Retorting failed to reduce mercury concentration below target level of 20 mg/kg in 8 out of 10 trials
- No information given on mercury levels in waste water and treated water
- No information given on mercury levels in Effluent Treatment Plant sludge
- Mercury levels in ambient air exceeded safe level of 0.025 mg/Nm3 in 4 out of 6 work spaces. It exceeded Stop Work level of 0.05 mg/m3 in three out of six work spaces, and reached a dangerous high of 0.1 mg/m3 in one work space
- “Treated soil” with mercury levels below 20 mg/kg was backfilled in violation of Detailed Project Report, which requires treated soil to be sent offsite to Total Storage Disposal Facility
Scientific Experts panel has agreed Unilever to submit an up scaling plan for final remediation to 20 mg/kg ignoring the trial remediation failure