Liquid Discharges

Where it comes from

Process drainage, wash-down water, storm-water, sea spray, rainwater and water generated from routine operations.

It may contain small quantities of oil, grease, metals, detergents (surfactants) and other residual chemicals present on the deck.

For safety reasons, run-off from areas containing LNG, mixed refrigerant or LPG is not contained to ensure that these do not develop into flammable gas clouds on the facility.

How it may impact environment

Small quantities of metal, chemicals or oil is discharged into the ocean which may affect water quality.

Biological receptors that come into contact with affected water may be impacted.

Mitigation strategies in place

• Drainage and bilge discharge will not be discharged if contamination levels are higher than defined acceptable levels.
• Drainage discharge will not be discharged if contamination levels are too high.
• Assurance will be undertaken of marine support vessels, including a check for valid and in date International Oil Pollution Prevention certificates as required by vessel class requirements.
• Spill kits are available on Prelude and marine support vessels to clean up small accumulations of contaminants.

Where it comes from

Grey water and sewage from accommodation, hospital, toilets, sinks, washbasins, showers, laundry and sweat drains.

Food waste is also macerated (softened and broken up) for disposal as liquid waste.

How it may impact environment

Extra nutrients discharged could increase turbidity, increase pathogens (bacteria, viral agents and / or parasites) or increase oxygen demand in the water.

Mitigation strategies in place

• Food wastes will be macerated to < 25 mm particle size if discharged within 500m of the FLNG.
• Vacuum toilets are designed to reduce sewage wastes to <25mm particle size prior to discharge to sea.
• Assurance will be undertaken of marine support vessels to check for valid and in date International Sewage Pollution Prevention Certificates, as required by vessel class requirements.
• Marine support vessels have a current Waste Management Plan (or equivalent) in accordance with MARPOL.

Where it comes from

Seawater is used for cooling and then discharged back into the ocean at slightly higher temperatures.

Chlorine is added to the cooling water to reduce the potential for any marine growth within the cooling system’s pipework.

How it may impact environment

Localised water quality may be impacted by increased chlorine levels discharged.

Chlorine has the potential to harm marine organisms in high doses.

Increased surface water temperatures may cause alteration of the physiological processes of exposed organisms.

Mitigation strategies in place

• The electrochlorination unit is maintained to ensure dosing is undertaken in a controlled manner.
• Online chlorine analysers are maintained and have associated critical alarms at defined limits.
• Online monitoring or manual sampling conducted to confirm free chlorine discharge do not exceed levels described in the full Environment Plan.