The study found degradation of crude oil was achievable using low-cost non-toxic agro-residues
A grave ecological concern has emerged in recent times: A surge in oil extraction through offshore drilling that has resulted in spillage of oil — accidentally or due to negligence. Industrial effluent discharge, waste burn-out and other manmade disasters polluting the marine environment are among other concerns.
Cleaning up of the oil spillage from the oceans without damaging the marine ecosystem is becoming an increasingly challenging task. The National Institute of Ocean Technology (NIOT) has developed an eco-friendly crude oil bioremediation mechanism technology using consortia of marine microbes wheat bran (WB) immobilized on agro-residue bacterial cells.
Bioremediation can be defined as any process that uses microorganisms or their enzymes to remove and or neutralize contaminants within the environment (i.e., within soil and water) to their original condition.
During the study, nine different hydrocarbon-degrading bacteria extracted from the ocean sediment and collected from a depth of 2,100 metres, were used.
These hydrocarbon degrading bacteria don’t depend on hydrocarbon for survival, but have a metabolic mechanism where they use petroleum products as carbon and energy source and thus, help cleaning up oil spills.
It was found that complete breakdown and degradation of crude oil was achievable using wheat bran marine bacterial consortia (which are low-cost non-toxic agro-residues) immobilised on low-cost nontoxic agro-residues bacterial cells in an environmentally sustainable manner.
It was also found that they were more effective in their immobilised state than the free bacteria cells in degrading the oil spills, in addition to being more versatile and resistant to adverse conditions.
The NIOT study found that immobilised bacterial cells had better oil degrading capacity than the free bacterial cells. They could remove 84 per cent of the oils within 10 days. The free bacterial cells degraded a maximum of 60 per cent of the crude oil at optimised conditions.
These findings evinced their efficacy in treating accidental bulk discharge of oil in marine environment through non-toxic clean-up technology.
In marine ecosystem, hydrocarbonoclastic deep sea microbial consortium (two or more group of bacteria) plays an important role in breaking down oil in the event of a spill. The microbial community serves as energetic primary degraders of complex mixture of petroleum hydrocarbons into various aldehydes, ketones and acidic metabolites.
Petroleum is a mixture of natural gas, condensate, and crude oil (viscous liquid mixture) consisting mainly of thousands of hydrocarbon compounds.
The present world crude oil production exceeds three billion tonnes a year, about half of which is transported through the sea routes. This, in turn, increases the risk of accidental oil spillage.
Oil spills have the potential to cause huge environmental damage: they end up accumulating in sub-surface sediments transferring the toxic organic materials to the marine food chain.
Deepwater horizon drilling accident was the largest accidental oil spill disaster in history that took place on April 20, 2010, releasing 779 million litres of crude oil into the Gulf of Mexico.
An oil spill accident at East China Sea on January 6, 2018 released more than 136,000 tonnes of volatile petroleum products.
The Ennore oil spill occurred outside the Kamarajar Port in Ennore near Chennai in Tamil Nadu on 28 January, 2017, when an outbound empty tanker BW Maple collided with an inbound loaded oil tanker Dawn Kanchipuram releasing at 9.9 million gallons (37,000 m3) of oils into Bay of Bengal.
An oil spill accident at East China Sea on January 6, 2018 released more than 136,000 tonnes of volatile petroleum products. Deepwater Horizon drilling accident was the largest accidental oil spill disaster in history that took place on April 20, 2010 releasing 779 million litres of crude oil into the Gulf of Mexico.
The recent MV Wakashio spill off Mauritius — about 1,000 tonnes of oil spilled into a sanctuary for rare wildlife after the Japanese ship struck a coral reef on 25 July, 2020.
Mixtures of hydrocarbons released to the surface of marine waters are widely dispersed into different depths and end up in sediments due to oil-particle aggregation, severely affecting the local marine environment.
Led by G Dharani, the research team comprised A Ganesh Kumar, N NivedhaRajan and R Kirubagaran of NIOT, Union Ministry of Earth Sciences. The research work was published in the Journal of Marine Pollution Bulletin.
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