The Extended Gravity Oil Water Separation (EGOWS) concept is an improvement on the industry-standard American Petroleum Institute (API) gravity separator that has been widely used for the last 60 years.

The API separator, originally designed for oil refineries, is not designed to reduce the oil content of water below about 100 parts per million and is not suitable for releasing water directly to the environment.

Regulatory requirements for the release of oil-contaminated water to the environment are becoming stricter worldwide. It is common for environmental protection authorities to impose a limit of 10 parts of oil per million of effluent water, and increasingly for there to be no visible sheen on the receiving water.

Although other systems can achieve low effluent oil contents, they tend to be more energy intensive and incur higher costs, particularly for ongoing maintenance, says David Tolmie, who developed EGOWS with colleague Peter Stone from the University's Water Research Laboratory in the School of Civil and Environmental Engineering.

"EGOWS can removes oil down to below 10 parts per million, requires no power and is most useful in situations that are unattended," says Mr Tolmie. "Most of the EGOWS installations to date in Australia have been in electricity substations to eliminate the small but potentially disastrous risk of a major spill of oil to the environment."

The system's secret lies in its ability to take episodic inflows of oily water and extend the time it spends in the separator tank.

Because oil is less dense, it rises to the surface of the water. The more time given to effluent water in the separator, the more oil that can be separated. EGOWS achieves a separation time of days in the tank
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Contact: Mary OMalley
m.omalley@unsw.edu.au
61-2-9385 2873
Research Australia
4-Aug-2005