Aquatic Pollution and Coastal Management

Unit 6 : Oil pollution

6.5.Control of Oil Pollution
Some common methods to control the oil pollution from marine areas and other bodies of water are briefly described below:

Mechanical Containment
The oil spills spread rapidly in the form of slicks which can be contained by means of some mechanical barriers. One such method is the use of floating containment barriers or booms. These are made up of relatively compatible plastic materials, such as polyethylene, polyurethane, polyvinyl chloride, nylon, neoprene, epoxies and polypropylene and contain inflated sacs at regular intervals for floatation. Any floating or spreading oil can be contained in them from where it can be removed by some other means.

Another technique is the use of bubble and current barriers which involves the generation of a surface current in opposite direction of spread of the oil by means of spray nozzles or by generating bubbles at a depth. A simple bubble discharger can be constructed with a submerged pipe with numerous air discharge pores along its length. Its major use is at oil loading terminals where it encircles them to protect the spread of spilled oil.

Dispersion Agents
The natural process of emulsification of oil in the water can be speeded up by spraying chemical dispersants on the oil slick from ships or aircrafts. However, dispersants are not effective against heavy oils and weathered oil and some of these chemicals may be toxic to life and can consume oxygen during their biodegradation. Dispersants are useful for treating small quantities of fresh oil.

Slick Lickers
A variety of slick lickers have been developed in which continuous belt of absorbent material dips through the oil slick and is passed through rollers to extract the oil. Slick lickers can deal with only a small quantity of oil and are useful in harbours and shelter waters polyurethane foams, polyethylene fibres, shredded polystyrene foam, wood cellulose fibres etc can also absorb oil.

Sinking Agents
The use of these agents is made only in deep waters where no fish catch is usually made. These agents are oleophilic and hydrophilic in nature with a high density. [The examples are: chalk treated with stealic acid, barite treated with latex, asbestos, carbonized treated sand, treated-fly ash etc.]

Burning Agents
Burning can provide a rapid disposal of a large quantity of oil in short period. However the volatile substances from the oil are rapidly evaporated leaving behind the oil which requires some support for combustion. A few agents supporting the combustion are straw, cellular glass beads and silage treated fume silica. All these substances work as wicking agents and can support combustion.

Biodegradation/ Bioremediation
Several components of the oil can be degraded by the micro-organisms. A number of experiments have demonstrated the possible use of bacteria in producing single cell protein from certain oil industry wastes. However the use of bacteria in natural degradation of oil in sea is still under experimental stage.

Bioremediation
This can be achieved by spraying the stranded oil with nutrients (nitrates and phosphates) to increase the bacterial degradation of the oil.