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Bioremediation: Cultivating microbes to clear our oil mess

Read time: 2 mins
10 Apr 2018

Researchers from National Institute of Technology, Durgapur and Indian Institute of Technology Kharagpur in West Bengal, with support from Department of Biotechnology, Government of India,have shown that the one way to efficiently deal with oil sludge, is to cultivate suitable microbes using nutrients, which then disintegrate the contaminants in the sludge.

Our world today is powered by fossil fuels, the source of which is the crude oil pumped out of the ground. India, which imports all its oil, alone imported around 4.5 Billion gallons per day of crude oil last year. Once petrol and other fuels like diesel, kerosene are removed, the remaining sludge is still ripe with chemicals like hexane, benzene, fluorine and naphthalene. Petroleum Industries worldwide generate about a billion ton of petroleum sludge each year. If left untreated, the sludge could cause severe environmental hazards, like pollution and poisoning of ecosystems.

Some microorganisms like Bacillus, Coprothermobacter, Rhodobacter, Pseudomonas, Achromobacter etc are known to degrade hydrocarbons. Bioremediation involves employing such microorganisms to degrade hydrocarbons in our petroleum sludge. The researchers suggest two ways of achieving efficiency with bio remediation: biostimulation and bioaugmentation.

Biostimulation involves stimulating the bacteria by suitably altering the environment in which they grow. In this case, the researchers used nutrients like nitrates, phosphates, or a mixture of the two to stimulate the growth of microorganisms which then degrades the waste sludge. However this process depends on the ability of the native and endemic microorganisms to degrade the sludge quickly, which often isn’t the case.

To aid the native microorganisms, the researchers suggest using bioaugmentation- a process of introducing other microorganisms that can do the job faster. The petroleum sludge can be home to millions of colonies of bacteria and other microorganisms. Of these, to successfully degrade the contaminants, fermentative, hydrocarbon degrading, sulfate-reducing, CO2-assimilating and methanogenic (methane producing) microorganisms are required. Although native microorganism already present in the sludge can have these properties, to accelerate the degradation, biosurfactant producing and hydrocarbon utilizing indigenous Bacillus strains were introduced along with the native organisms.

The study showed a 46-55% higher rate of degradation was observed with the addition of nutrients or after biostimulation and and 57-75% reduction of contaminants with the addition of the bacillus strains. The researchers believe “nutrients induced community dynamics and metabolic interplay” could be the reasons for the accelerated bioremediation. According to the researchers, “This study recommends the addition of nutrients along with potential endogenous hydrocarbon degraders in the sludge for the bioremediation of otherwise recalcitrant petroleum refinery waste”