A thick oily tide from the sea lapped at the coast of several fishing hamlets in north Chennai, a day after two cargo ships, one of them an oil tanker, collided off Kamarajar Port.
Several dead turtles and hatchlings coated with the black oil were washed ashore and discovered among the boulders.

Cause of the accident
Of the two ships, coming from Mumbai with a full load of petrol and diesel collided with an LPG tanker.

Oil Spill containment measures taken immediately
Since there was a spill from the oil vessel, the Ennore Kamarajar Port authorities placed containment booms around the ships. A Pollution Response team from the Coast Guard reached the spot and plan to employ bio-remediation techniques to control oil spill.

It refers to the cleaning of environment with the help of living organisms. Living organisms range from micro-organisms to different species of plants. For eg: Bacteria help in decomposition of organic waste. Certain plant species such as mustard helps in absorption of poisonous elements such as selenium.
Bioremediation usually takes a longer time period. However, bioremediation effectively discriminates between pollutants and the required nutrients.

Strategies of Bioremediation
1. In situ bioremediation techniques
It refers to the treatment of waste at its site. These techniques can assist in the degradation of adsorbed fuel residuals, but also assists in the degradation of volatile organic compounds. In-situ bioremediation techniques are:

a. Biosparging:
Biosparging is an in situ remediation technology that uses indigenous microorganisms to biodegrade organic constituents in the saturated zone. In biosparging, air (or oxygen) and nutrients are injected at high pressure to increase the biological activity of the indigenous microorganisms and enhance their decomposition activity.

b. Bioventing:
Bioventing is an in situ remediation technology that uses microorganisms to biodegrade organic constituents adsorbed in soils in the unsaturated zone. Bioventing enhances the activity of indigenous bacteria and simulates the natural in situ biodegradation of hydrocarbons in soil by inducing air or oxygen flow at low pressure into the unsaturated zone and, if necessary, by adding nutrients. In conventional bioventing systems, oxygen is delivered by an electric blower to subsurface wells.

Note: Saturated zone requires injection of air and nutrients at high pressure and unsaturated zone requires injection of air and nutrients at low pressure.

c. Bio augmentation:
Micro–organisms are imported to a contaminated site to carry out degradation of organic waste.  For instance, Oil Zapper (explained earlier)

2. Ex-Situ bioremediation techniques
Ex–situ refers to the transfer of contaminated material for treatment to some other site. Ex-situ bioremediation techniques are:

1. Land farming
Contaminated soil is spread over a prepared bed. The soil is periodically tilled to stimulate growth of micro-organisms for degradation of organic waste.

2.Bio pile
Bio-pile is a hybrid of Land farming and Composting. Excavated soils are spread over a prepared bed, formed into compost piles and enclosed for treatment.

Moisture, heat, nutrients, oxygen, and pH are controlled to enhance biodegradation. An irrigation/nutrient system is used to pass air and nutrients through the soil. Soil piles can be up to the height of 20 feet. They may be covered with plastic to control runoff, evaporation and to promote solar heating.

Treatment time is typically 3 to 6 months, after which the excavated material is either returned to its original location or disposed off.

The treatment area is generally covered or contained with an impermeable lining to minimize the risk of contaminants leaching into an uncontaminated soil.