Response techniques when the cargo has been released

Reducing the vapours emitted by evaporators

In port areas, two techniques may be employed to reduce evaporation and restrict the spreading of vapours. The first involves reducing vapours using water spray curtains, which dilute the toxic cloud, reduce the concentration of gas and limit the size of the danger area. This is effective on hydrophilic• products. The second technique involves spreading a
layer of foam over the pollutant to reduce its evaporation rate.

Containment and filtration of dissolvers in water

When a soluble substance is spilt in a port or harbour, it is sometimes possible to contain the pollution by shutting off the doors of a drydock facility or the sluice gates•. The pollutant can then be treated using mobile truck-mounted units. These units are composed of high flow rate pumps which send the polluted water through large filter cartridges that retain the pollutant.

Recovery of sinkers

In coastal or port areas, sinking substances can be recovered on the bottom by dredging. This mud and sediment mechanical a excavation• technique is implemented by vessels or a barges• equipped with a a dredge• which may simply consist of buckets or be fitted with pumps. The waste collected is loaded onto the vessel to be treated in specialized centres on land.

Containment, recovery and dispersion of floaters

The response equipment used for persistent floating products (vegetable oils and viscous chemicals) are inspired by those existing for oil pollution, but are preferably made of materials resistant to the chemicals in question.

Containment and recovery: when floating substances form a sufficiently thick and continuous slick, they can be contained by deploying floating booms then recovered using a skimmers• if the sea and weather conditions allow.

Dispersion: dispersants are products which speed up the natural dispersion of pollutants in the water column, by taking advantage of wave agitation. They help to fragment slicks into a multitude of microdroplets spread throughout the water column, which speeds up their breakdown and bioassimilation in the marine environment. Because of dispersants'
mode of action, their use is regulated. They should not, for instance, be used in areas where dilution levels are too low.

Trawling: if the pollutant is a paste, it can be recovered offshore using trawl nets• towed by a single or pair of vessels.

Sorbents: these products can be used in coastal or port areas on small-scale spills. They are solid materials used to retain floating substances by sorption, in order to facilitate their subsequent recovery.

On land clean-up: when large quantities of vegetable oil agglomerates are washed up on difficult access sites (riprap•, pebble beaches), manual recovery is necessary. If the areas affected are sandy beaches, specialized equipment such as sand screeners• can be used.

When the oil on the shoreline is liquid, the area can be cleaned at low tide by flushing• with cold water. The effluent• is recovered and settled, before pumping off the oil.