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This publication is available at https://www.gov.uk/government/publications/how-to-use-oil-spill-treatment-products-and-equipment/oil-spill-treatment-product-types-health-and-safety-and-training
Dispersants are chemicals that, when applied to oil floating on the surface of the sea, greatly increase the rate of dispersal, and therefore breakdown, of the oil. Dispersants are categorised into:
- Type 1: Hydrocarbon solvent-based dispersant used undiluted
- Type 2: Concentrates, diluted 1:10 with seawater before use
- Type 3: High efficacy concentrates used undiluted
Dispersants assist the natural process where the mechanical action of the sea can break down oil into small droplets. Some of these will be dispersed and diluted by the water’s movements. Dispersants can offer substantial protection to seabirds and mammals, and can also protect coastline environments by dispersing the oil before it comes ashore. Dispersants will temporarily increase hydrocarbon concentrations and can increase the hazard to water column and seabed dwelling resources including some important fishery (in particular shellfisheries) interests.
Dispersants can be very effective in preventing damage to wildlife and recreational amenities in coastal areas. However, by increasing the volume of oil in the water column, they may also adversely affect the quality of commercially exploited fish and shellfish, and the marine environment in general.
Dispersant use may also have a harmful effect in shallow waters where there is limited scope for the dispersed oil to be diluted. Their use is regulated in sea depths of fewer than 20 metres or within 1 nautical mile of such depths. The use of a dispersant and other oil spill treatment products must be approved in such areas. You would normally be advised on whether their use was suitable in deeper, offshore waters – in particular protected areas that are offshore or near sensitive or vulnerable species and habitats.
Before using dispersants you should consider the type of oil involved and its degree of weathering and dispersion into the water column. Sea, weather and temperature conditions also need to be considered, as well as the volume of oil spilt.
Light oils such as middle distillates like gasoline, kerosene and diesel fuel should not be treated with dispersants. These oils are more toxic than the heavier oils and if dispersed into the water column rather than left to evaporate are more likely to harm marine organisms within the water column.
Dispersants can successfully treat light crude oils, light residual fuel oils and lubricating oils. Their use on heavy residual fuel or crude oils is unlikely to be effective and should generally be avoided.
Before deciding to use a dispersant or other product, a judgement is made between the possible effects of using the product and the consequences of allowing the oil to remain untreated.
The Marine Management Organisation (MMO) will consult fisheries scientists and those who have expertise in the marine and coastal environment of the area concerned. In particular, statutory nature conservation agencies must be consulted. It is essential that a judgement is made as quickly as possible, as many types of oil quickly become resistant to treatment due to weathering.
Provided a dispersant is approved at the time of its manufacture, it may continue to be held in stock and used for the treatment of oil spills even if the approval has expired.
Stockholders are required to arrange for 1 sample from each bulk tank to be retested for the product’s ability to do its job (efficacy) every 5 years.
Where dispersants remain sealed in the manufacturer’s original packaging, the initial retest can be carried out after 10 years. After that initial period retesting must continue every 5 years.
Stored products are tested for efficacy using the same standard laboratory-based procedure for dispersant approval as described in Annex 1 to Appendix A WSL Report LR448 (PDF, 157KB). Some loss of efficacy is allowed. The pass rate is set at 75% of the original minimum standard of efficacy. Contact MMO for more information on the retesting requirements.
These are chemicals used to separate oil and water. They can be used with dispersants when the type of oil prevents chemical dispersion. Some dispersants also act as demulsifiers.
3. Surface cleaners
Surface cleaners are chemicals that, when applied to oil covered hard surfaces, increase the rate of dispersal from the surface, aiding cleaning.
4. Bioremediation products
Bioremediation accelerates the natural degradation process through adding nutrients, micro-organisms, or both. Products improve how oil breaks down by containing, or improving the growth of naturally occurring, oil-degrading bacteria. The process takes time and the bioremediation agents may be diluted.
Sorbents absorb oil and are usually in the form of powder, granules or beads. They are either absorbent (they take some liquid into themselves) or adsorbent (forms a layer on the surface of the oil) materials and can be synthetic or natural, packaged or loose. It is important to identify waste disposal routes for the used and oily materials.
Degreasers are used for cleaning grease from machinery of ships and marine structures.
7. Burning oil in situ
The Maritime and Coastguard Agency’s (MCA) National Contingency Plan clearly states that it is not considered a viable option in UK waters as it causes atmospheric pollution.
8. Health and safety
Dispersants should always be used in line with the manufacturer’s supplier’s instructions. In addition to these, a number of regulations apply.
Safety during the use of oil dispersants is regulated by Control of Substances Hazardous to Health Regulations (COSHH) and the associated approved codes of practice, although these regulations do not apply to ships’ crew. The regulations apply to hazardous substances as defined and require employers to:
- perform a risk assessment
- control exposure, so far as is reasonably practicable, by means other than the use of personal protective equipment (PPE)
Product containers should be clearly labelled and the suppliers’ labels should not be changed or obscured. The labelling should be chemical resistant and weatherproof, and preferably fixed to the container in 2 places to avoid being obscured when containers are stacked.
Dispersants will normally need to be maintained at a constant temperature, preferably in the range -10 to +30 degrees Celsius. Changes in storage temperature can encourage condensation to form, to the detriment of the contents and container.
Dispersants stored in plastic containers should be kept out of sunlight.
Where dispersants are kept in bulk tanks, a log should be kept of the contents and use.
If products are changed, or a new batch is introduced into a bulk tank, the tank must be completely drained and flushed clean before being refilled.
Products must be retested periodically to ensure continuing efficacy. Dispose, in strict accordance with the suitable waste disposal regulations, of any that do not meet 60% of the original minimum standard of efficacy.
Be aware that the contents of partially filled containers can deteriorate quite quickly. Never mix products, either in storage or during application, unless the manufacturer’s or supplier’s instructions state how to mix them safely.
10. Safe handling and disposing of products
You should only handle products in well-ventilated areas away from heat, sparks and naked flames. You should treat dispersants as potentially combustible and any fires should be extinguished using carbon dioxide, chemical powder, foam, sand or earth. Larger fires may be fought using water fog.
You should mop up spillages quickly using a suitable sorbent. The area can be flushed using large quantities of water, but make sure that most of the dispersant is prevented from draining away by mopping up or creating a suitable barrier.
If a dispersant comes into contact with the eyes or skin, treat the affected area with prolonged fresh water flushing. You should seek medical advice if irritation persists.
Avoid dispersants coming into contact with painted surfaces.
You should dispose of redundant stocks of dispersant within the normal framework of legislation for the disposal of chemical waste. The main legal requirements are contained in the Waste Management Licensing Regulations 1994 and the Control of Pollution (Special Waste) Regulations 1980, as amended by the Special Waste (Amendment) Regulations 1996. Redundant dispersants with a hydrocarbon base must be dealt with as special wastes that require incineration.
You should make sure that those who handle, store or use dispersants are properly trained. The Maritime and Coastguard Agency (MCA) has accredited oil spill training courses [link] which include advice on the use of dispersants.
You should make sure that all those involved with dealing with an oil spill incident are aware of contingency plans and the procedure for approving and controlling the use of dispersants.
Check that the manufacturer’s instructions for the safe and effective handling of a dispersant are followed at all times. A material safety data sheet should also be complied with and readily available for reference.