Illegal bilge discharge is nothing new, but despite regulations in effect for over two decades, there is still confusion and a willingness to bend the rules, risking costly penalties. At Rivertrace, we help our customers in marine, offshore, and industrial sectors run environmentally compliant operations efficiently. We advise on, supply, and support devices that actively measure, monitor, and control oil levels in water to prevent pollution and ensure bilge discharge compliance.
Illegal bilge discharge has remained a major issue in the maritime industry despite environmental regulations being in place for more than two decades. While most ship operators understand the importance of compliance, misunderstandings around equipment setup and operational procedures can still result in serious violations, detentions, and financial penalties.
At Rivertrace, we support marine, offshore, and industrial operators with advanced monitoring technologies designed to measure, monitor, and control oil levels in water. These systems help ensure vessels remain compliant with bilge discharge regulations while protecting the marine environment.
AMSA Marine Notice & MEPC.107(49) Inspections
Earlier this year, the Australian Maritime Safety Authority (AMSA) issued a Marine Notice providing guidance to port authorities regarding the testing and inspection of MEPC.107(49) compliant equipment.
This guidance has created concern across parts of the industry, particularly where vessels have faced detention without fully understanding the underlying compliance issue.
AMSA specifically interprets the failure of a 15ppm bilge alarm to activate the automatic stopping device — in situations where a representative sample of effluent is not present — as non-compliance with Resolution MEPC.107(49).
Representative Sampling Requirements
Under MEPC.107(49) guidelines, section 6.2.2 states:
“The arrangement on board ship for the extraction of samples from the 15 ppm Bilge Separator discharge line to the 15 ppm Bilge Alarm should give a truly representative sample of the effluent with adequate pressure and flow.”
This requirement is critical because the oil content monitor (OCM) can only function correctly if it receives a continuous and representative flow sample from the oily water separator (OWS).
If the sample flow is interrupted, restricted, or manipulated, the system may fail to accurately detect oil content levels, potentially resulting in illegal discharge.
Why Continuous Sample Lines Matter
Rivertrace strongly recommends that the pipe connecting the oily water separator to the 15ppm Oil Content Monitor (OCM) should consist of one continuous pipe section without interruption.
Installing valves within this section can create opportunities to manipulate flow and pressure conditions, which may affect the accuracy of the monitoring system and compromise bilge discharge compliance.
This interpretation is further supported by the Piping & Instrumentation Diagram (P&ID) referenced under section 6.2.3 of MEPC.107(49), which does not indicate any valve or break between the OWS and the OCM sample line.
Common Compliance Risks
Several operational issues can increase the risk of non-compliance during bilge discharge operations, including:
- Interrupted sample flow
- Incorrect pipe arrangements
- Manipulation of flow pressure
- Failure of automatic stopping devices
- Poor maintenance of OCM systems
Even unintentional setup issues can result in Port State Control findings, vessel detention, or environmental penalties.
Recommended Steps for Bilge Discharge Compliance
To help operators maintain compliance with MEPC.107(49), Rivertrace recommends the following best practices:
Use a Continuous Pipe Arrangement
Ensure the pipe between the oily water separator and the oil content monitor remains one uninterrupted continuous section.
Secure Existing Valves
If valves are already installed and cannot be removed, they should be secured and sealed in the open position to prevent any manipulation of pressure or flow during operation.
Install a Flow Switch
Adding a flow switch to the SMART BILGE system helps ensure the OCM generates an alarm if there is no sample flow through the measuring cell during normal operation.
Maintain Regular Inspections
Regular inspections, calibration checks, and maintenance help ensure monitoring systems continue operating correctly and remain compliant with international regulations.
Supporting Environmentally Compliant Operations
Bilge discharge compliance is not only about avoiding penalties — it is also about protecting marine ecosystems and maintaining safe, environmentally responsible operations.
By using reliable monitoring systems and following best-practice installation guidelines, operators can significantly reduce compliance risks while improving operational confidence during inspections and audits.
How Rivertrace Supports Compliance
Rivertrace continues to support shipowners and operators through advanced oil-in-water monitoring technologies, technical guidance, and compliance solutions.
From SMART BILGE systems to flow switch upgrades and calibration support, Rivertrace helps operators maintain reliable monitoring performance and meet evolving environmental standards.
To ensure bilge discharge compliance, Rivertrace recommends the following steps:
- Ensure the pipe from the OWS to the OCM is one continuous pipe.
- If valves are fitted on this line and cannot be removed, secure and seal them open to prevent manipulation of flow and pressure during operation.
- Fit a Flow Switch to your SMART BILGE to ensure the OCM alarms if there is no flow through the measuring cell during normal operations.
Contact the Rivertrace team for further clarification or to upgrade your flow switch.
Frequently Asked Questions (FAQs)
What is bilge discharge compliance?
Bilge discharge compliance refers to following MARPOL and MEPC regulations governing the discharge of oily bilge water from ships.
What is MEPC.107(49)?
MEPC.107(49) is an IMO resolution that defines standards and guidelines for oily water separators and 15ppm bilge alarm systems.
Why is representative sampling important?
Representative sampling ensures the oil content monitor receives an accurate sample of the discharge water, allowing it to correctly detect oil levels.
Can valves affect bilge discharge compliance?
Yes. Valves installed between the oily water separator and oil content monitor can affect sample flow and pressure, potentially compromising compliance.
What does a flow switch do in a SMART BILGE system?
A flow switch detects whether there is proper flow through the measuring cell and triggers alarms if flow is interrupted during operation.