Oily water separator (OWS)
The OWS is designed with two main elements:
- the separator that separates oil and water
- the discharge monitoring device that measures the oil content of the discharged liquid.
An operational OWS is the evidence that we require to be reasonably certain that the ship complies with MARPOL.
The permitted level for oil discharge is generally 15 parts per million oil in water—a concentration at which oil is not normally visible. If permitted oil content levels are exceeded, an alarm is triggered and the discharge is shut down.
When checking OWS regularly and before an AMSA inspection, make sure to check:
- all oil record book entries completed according to MARPOL
- OWS is working properly
- that there is no oil in the discharge
- the alarm and stopping device is operational.
If any of these are found to be deficient or your oil record book is not accurately filled out, your ship may be detained.
If clear grounds exist, our inspector may also ask for a section of piping after the monitor be removed for internal inspection.
Sewage treatment plant (STP)
If a vessel is fitted with a STP it should be operational, but may not be in operation if the vessel is directing sewage to a designated sewage holding tank.
Our surveyors regularly find that the STP is not being operated correctly, often being turned on just before entering Australian waters and the plants that use bacteria to process the sewage do not have enough time to produce bacteria. Our inspectors have found internal chambers to be severely wasted, or valves incorrectly positioned so that raw sewage may be inadvertently discharged overboard.
When checking the STP regularly and before an inspection, make sure to check:
- that the ships crew are familiar with the operation and maintenance of the treatment plant
- the treatment plant is operated as required by the manufacturer’s instructions and in compliance with MARPOL
- the safety management system onboard includes the above steps for regular checks.
If any of these are found to be deficient, your ship may be detained.
