Hotel Service Unit 19 Q8

An Oily Water Bilge Separator (OWS) is a vital piece of equipment on board ships, specifically designed to separate oil and other contaminants from bilge water and other oily wastewater generated during ship operations.

Its main purpose is to ensure compliance with MARPOL Annex I regulations, which set strict limits on the amount of oil that can be discharged into the marine environment.

1. Oily Water Separators: How Do Bilge Water Treatment Systems Work? – H2O LLC

2. Oily water separator (marine) – Wikipedia

Key Functions:

• Separation: The OWS utilizes various physical and chemical processes, such as gravity separation, coalescence, and sometimes centrifugation, to effectively separate oil and other contaminants from water.
• Compliance: It ensures that the treated water, known as effluent, meets the MARPOL Annex I discharge limit of 15 parts per million (ppm) oil content before being released overboard.   1. Marpol Annex I Part A – The Master Mariner www.themastermariner.com
• Environmental Protection: By efficiently removing oil and contaminants, the OWS plays a critical role in preventing marine pollution and protecting the marine ecosystem.

Components of a Typical OWS:

• Inlet: The oily water mixture enters the OWS through an inlet pipe, often equipped with a strainer to remove coarse debris.   1. Oily Water Separator — Working Principle and Construction | by MarinersPoint | Medium medium.com
• Separation Chamber: This is the main body of the OWS where gravity separation occurs, allowing oil droplets (being less dense) to rise to the surface.
• Baffles/Plates: Baffles or plates may be present to enhance separation and increase the surface area for oil to collect.   1. Baffle Plate Configuration to Enhance Separation in Horizontal Primary Separators www.researchgate.net
• Coalescer: Many OWS systems also include a coalescer unit that uses special filter media to further coalesce (combine) smaller oil droplets into larger ones, making them easier to separate.
• Oil Collection Chamber: Located at the top, this area collects the separated oil, which is then removed by a skimmer or overflow system.   1. Oily water separator (marine) – Wikipedia en.wikipedia.org
• Clean Water Outlet: The treated water, now with significantly reduced oil content, exits the OWS through an outlet pipe.
• Oil Content Monitor (OCM): A sensor continuously monitors the oil content of the treated water before discharge. If the oil content exceeds 15 ppm, it triggers an alarm and may automatically stop the discharge or recirculate the water for further treatment.   1. Understanding Oil in Water Monitoring – Rivertrace rivertrace.com

Types of OWS:

• Gravity Plate Separators: Rely primarily on gravity separation and baffles/plates.   1. Oily Water Separators | Officer of the Watch officerofthewatch.com
• Coalescer Separators: Incorporate coalescing filters to enhance oil droplet separation.   1. How Does a Coalescer Work & What is a Coalescing Filter? – Integrated Flow Solutions ifsolutions.com
• Centrifugal Separators: Utilize centrifugal force to accelerate the separation process, often used for higher flow rates or more challenging oily water mixtures.   1. Different types of Marine Oily Water Separators separatorequipment.com

Importance of OWS:

• Environmental Protection: Crucial for preventing marine pollution and protecting delicate marine ecosystems.
• Regulatory Compliance: Essential for complying with MARPOL regulations and avoiding penalties or detentions.   1. Oily water separator – Further clarifications on requirements for sampling points – DNV www.dnv.com
• Operational Efficiency: Enables the safe and legal discharge of treated bilge water, reducing the need for storage and disposal ashore.

Maintenance:

• Regular maintenance is vital to ensure the OWS operates efficiently and meets regulatory requirements. This includes cleaning, filter replacements, and calibration of the OCM.   1. Maintaining An Oily Water Separator: 6 Key Parts to Replace on Time www.h2oinc.com

In summary, the Oily Water Bilge Separator is a critical piece of equipment on ships that helps prevent oil pollution and protect the marine environment. It enables the safe and compliant discharge of treated bilge water and other oily wastewater, promoting responsible and sustainable maritime practices.  

1. Oily water separators: Sizing the Correct OWS System – H2O LLC

In the context of Oily Water Bilge Separators (OWS), turbulent flow refers to a flow regime characterized by chaotic and irregular fluid motion. Unlike laminar flow, where fluid particles move in smooth, parallel layers, turbulent flow involves eddies, swirls, and fluctuations in velocity and pressure.  

1. Laminar and turbulent flow – Vapourtec

2. Laminar flow | Definition & Facts – Britannica

Effects of Turbulent Flow on OWS Performance:

• Hinders Separation: Turbulent flow can disrupt the gravity separation process in the OWS. The chaotic mixing of oil and water makes it difficult for oil droplets to rise to the surface and coalesce, reducing separation efficiency.
• Re-entrainment of Oil: The swirling motion can re-entrain already separated oil droplets back into the water stream, further compromising the separation process and increasing the oil content in the effluent.   1. Oily Water Separator — Working Principle and Construction | by MarinersPoint | Medium medium.com
• Reduced Coalescer Efficiency: In coalescer-type OWS, turbulent flow can hinder the coalescing of small oil droplets into larger ones, reducing the effectiveness of the coalescing media.
• Increased Filter Clogging: Turbulent flow can carry more debris and solids into the filters, causing them to clog more quickly and requiring frequent cleaning or replacement.

Why Turbulent Flow is Undesirable in OWS:

• Non-compliant Discharge: If the OWS cannot efficiently separate oil due to turbulent flow, the discharged water may exceed the MARPOL limit of 15 ppm oil content, leading to environmental pollution and potential penalties.
• Reduced Operational Efficiency: Inefficient separation may require the bilge water to be recirculated through the OWS multiple times, increasing energy consumption and delaying operations.
• Equipment Wear and Tear: Turbulent flow can cause increased wear and tear on the OWS components due to the fluctuating pressures and velocities.

Measures to Minimize Turbulent Flow:

• Controlled Flow Rate: Maintain the bilge water feed rate within the OWS’s designed capacity to avoid overloading and excessive turbulence.
• Baffles and Flow Control Devices: The OWS is designed with baffles, weirs, and other flow control devices to create a more laminar flow pattern and minimize turbulence within the separation chamber.
• Proper Piping and Design: Ensure smooth transitions and avoid sharp bends or restrictions in the piping connected to the OWS, which can create turbulence.
• Regular Maintenance: Keep the OWS clean and well-maintained, ensuring that filters, coalescers, and other components are functioning correctly and not contributing to turbulence.

Conclusion:

Turbulent flow is detrimental to the efficient operation of an Oily Water Bilge Separator. By controlling the flow rate, maintaining the system, and adhering to proper design principles, operators can minimize turbulence and ensure effective oil-water separation, ultimately contributing to environmental protection and compliance with MARPOL regulations.  

1. Oily Water Separator — Working Principle and Construction | by MarinersPoint | Medium

In the context of Oily Water Bilge Separators (OWS), an emulsion refers to a mixture of two immiscible liquids (liquids that don’t normally mix), like oil and water, where one liquid is dispersed as small droplets within the other.

Types of Emulsions:

• Oil-in-Water Emulsion: Oil droplets are dispersed in a continuous water phase. This is the most common type encountered in bilge water.
• Water-in-Oil Emulsion: Water droplets are dispersed in a continuous oil phase. This type is less common in bilge water but can occur in certain situations, like fuel contamination.

Challenges in OWS Operation:

Emulsions pose a significant challenge to OWS operation because the tiny oil droplets are difficult to separate from the water using conventional gravity or coalescence methods.

• Hinders Separation: The small size and stability of the oil droplets prevent them from readily rising to the surface or coalescing into larger droplets, making separation less efficient.
• Increased Oil Content in Effluent: This can lead to the treated water (effluent) exceeding the permissible oil content limit of 15 ppm, resulting in non-compliance with MARPOL regulations and potential pollution.
• Clogging of Filters and Coalescers: The emulsified oil droplets can clog filters and coalescers, reducing their effectiveness and requiring more frequent cleaning or replacement.

Factors Contributing to Emulsion Formation:

• Surfactants: Substances like detergents, soaps, or chemicals present in the bilge water can act as surfactants, reducing the surface tension between oil and water and promoting emulsion formation.
• Agitation and Turbulence: Mechanical agitation, such as from pumps or propellers, can create turbulence and shear forces that break down oil into smaller droplets, facilitating emulsification.
• Temperature: High temperatures can also contribute to emulsion stability by reducing the viscosity of the oil and making it more easily dispersed in water.

Strategies to Deal with Emulsions:

• Choose the Right Detergent: Select bilge cleaning detergents that are specifically formulated to minimize emulsion formation (“quick break” detergents).
• Control Flow Rate: Avoid excessive flow rates through the OWS, as turbulence can promote emulsification.
• Chemical Treatment: In some cases, chemical demulsifiers may be added to the bilge water to break down emulsions and improve separation efficiency.
• Advanced Separation Technologies: Some OWS systems incorporate additional technologies like centrifugation or electrocoagulation to enhance the separation of emulsified oil.

Conclusion:

Emulsions pose a challenge to the effective operation of oily water separators. By understanding the causes of emulsion formation and implementing preventive measures, such as careful detergent selection and proper flow control, ship operators can minimize the impact of emulsions on OWS performance, ensure compliance with MARPOL regulations, and contribute to the protection of the marine environment.

In the context of Oily Water Bilge Separators (OWS), the maximum flow rate refers to the highest volume of oily water mixture that can be processed by the separator per unit time while still achieving the required oil removal efficiency.

Importance of Maximum Flow Rate:

• Efficiency: It’s crucial to operate the OWS within its designed maximum flow rate to ensure effective separation of oil and water.
• Compliance: Exceeding the maximum flow rate can lead to incomplete separation, resulting in the discharge of water with oil content above the permissible limit (15 ppm) as per MARPOL regulations.
• Equipment Protection: Operating beyond the designed capacity can put excessive stress on the OWS components, leading to potential damage or premature wear.

Factors Influencing Maximum Flow Rate:

• OWS Design and Size: Different OWS models have varying capacities and maximum flow rates based on their design, size, and the specific separation technologies used.
• Oil Type and Concentration: The type and concentration of oil in the bilge water can influence the separation process and the maximum flow rate the OWS can handle effectively.
• Temperature: The temperature of the oily water mixture can also affect separation efficiency. Higher temperatures generally improve separation but can also impact the OWS’s components and materials.   1. Oily Water Separator — Working Principle and Construction | by MarinersPoint | Medium medium.com

Operational Considerations:

• Monitoring Flow Rate: It’s essential to monitor the flow rate of bilge water entering the OWS and adjust it accordingly to stay within the permissible limit.
• Avoiding Overloading: Don’t exceed the OWS’s maximum flow rate, even if it means slowing down the bilge pumping process.
• Regular Maintenance: Proper maintenance and cleaning of the OWS are crucial to ensure it operates at its designed capacity and maintains separation efficiency.

Typical Maximum Flow Rates:

• The maximum flow rate for an OWS can vary widely depending on the model and size.   1. Oily Water Separators: How to Size A Bilge Water Treatment System – H2O LLC www.h2oinc.com
• Smaller OWS units on yachts or smaller vessels may have flow rates in the range of a few cubic meters per hour, while larger systems on commercial ships can handle tens or even hundreds of cubic meters per hour.

Consequences of Exceeding the Maximum Flow Rate:

• Non-compliant Discharge: Incomplete separation leads to higher oil content in the effluent, potentially exceeding the MARPOL limit and causing marine pollution.
• Alarm Activation and Shutdown: The Oil Content Monitor (OCM) will trigger an alarm if the oil content exceeds the limit, often leading to automatic shutdown or recirculation of the water.   1. Oil content meter – Wikipedia en.wikipedia.org
• Equipment Damage: Overloading the OWS can cause mechanical stress and premature wear on its components.

In summary, understanding and adhering to the maximum flow rate of an OWS is essential for ensuring its effective operation, compliance with environmental regulations, and the protection of the marine environment.

In the context of Oily Water Bilge Separators (OWS), coalescence refers to the process where small, dispersed oil droplets in the oily water mixture combine or merge to form larger droplets.  

1. Oily water separator (marine) – Wikipedia

This process is crucial for the effective operation of the OWS, as larger oil droplets are more easily separated from water due to their increased buoyancy and reduced surface area-to-volume ratio.  

1. Oily Water Separator (OWS) Explained – saVRee

How Coalescence Works in OWS:

• Coalescer Media: Most modern OWS systems incorporate a coalescer unit, which contains a specially designed coalescing media, often made of oleophilic (oil-attracting) materials like polypropylene or other synthetic fibers.   1. Oily Water Separators: How Do Bilge Water Treatment Systems Work? – H2O LLC www.h2oinc.com
• Adhesion and Coalescence: As the oily water mixture passes through the coalescer media, the small oil droplets adhere to the oleophilic surface.
• Growth and Release: These adhered droplets continue to attract and merge with other oil droplets, gradually increasing in size. Eventually, the larger droplets become heavy enough to detach from the media and rise to the surface of the water due to their buoyancy.   1. Oily Water Separator (OWS) Explained – saVRee www.savree.com

Benefits of Coalescence in OWS:

• Improved Separation Efficiency: Coalescence significantly enhances the separation of oil from water, especially for smaller and more dispersed oil droplets that may not be efficiently removed by gravity alone.   1. Oily Water Separator (OWS) Explained – saVRee www.savree.com
• Compliance with Regulations: By improving separation efficiency, coalescence helps ensure that the treated water (effluent) meets the MARPOL Annex I discharge limit of 15 ppm oil content.
• Reduced Environmental Impact: Efficient oil removal minimizes the risk of marine pollution and its associated harmful effects on ecosystems and marine life.

Factors Affecting Coalescence:

• Coalescer Media: The type, surface area, and condition of the coalescer media play a crucial role in its effectiveness. Regular cleaning and replacement are essential to maintain optimal performance.   1. How Does a Coalescer Work & What is a Coalescing Filter? – Integrated Flow Solutions ifsolutions.com
• Flow Rate: The flow rate of the oily water through the coalescer affects the contact time between the oil droplets and the media. Excessively high flow rates can reduce coalescence efficiency.
• Oil Properties: The type, viscosity, and temperature of the oil can influence its tendency to coalesce. Some oils may require specific coalescer materials or additional treatment steps to facilitate effective separation.
• Water Chemistry: The presence of surfactants or detergents in the bilge water can hinder coalescence by stabilizing oil droplets and preventing them from merging.

In summary, coalescence is a vital process in OWS that improves oil-water separation efficiency by promoting the merging of small oil droplets into larger ones. It helps ensure compliance with environmental regulations, minimizes marine pollution, and contributes to the overall effectiveness of the OWS system.  

In the context of Oily Water Bilge Separators (OWS), the interface refers to the boundary or separation layer between the oil and water phases within the separation chamber of the OWS.

Key Points about the Interface:

• Dynamic Zone: The interface is not a static line but a dynamic zone where oil and water are in the process of separating.
• Clarity and Definition: Ideally, the interface should be clear and well-defined, allowing for effective separation and removal of the oil layer.
• Influencing Factors: Several factors can influence the clarity and stability of the interface:
  • Oil Type and Viscosity: Heavier and more viscous oils tend to form a more distinct interface compared to lighter oils.
  • Water Turbulence: Excessive turbulence within the separation chamber can disrupt the interface and hinder separation.
  • Emulsification: The presence of surfactants or detergents can create stable emulsions, where tiny oil droplets are dispersed throughout the water, making it difficult to form a clear interface.
  • Temperature: Temperature can affect the viscosity of the oil and the separation process. Higher temperatures generally improve separation.

Importance of the Interface:

• Separation Efficiency: A clear and well-defined interface is crucial for the efficient operation of the OWS. It allows for the effective removal of the separated oil layer using skimmers or overflow systems.
• Compliance with Regulations: Maintaining a clear interface helps ensure that the treated water (effluent) has a low oil content, complying with MARPOL discharge limits.
• Operational Monitoring: The interface level can be monitored visually or using level sensors to assess the OWS’s performance and identify any potential problems.

Maintaining a Clear Interface:

• Control Flow Rate: Operate the OWS within its designed flow rate to minimize turbulence and promote a stable interface.
• Minimize Emulsification: Avoid the use of detergents or other chemicals that can create stable emulsions. Use “quick break” detergents designed for bilge cleaning that readily separate from oil and water.
• Regular Maintenance: Keep the OWS clean and well-maintained, ensuring that baffles, plates, and coalescer elements (if present) are free from debris or fouling that could disrupt the interface.
• Chemical Treatment (if necessary): In cases of persistent emulsion problems, chemical demulsifiers may be used to break down emulsions and improve interface clarity.

By carefully managing the factors that influence the interface and implementing appropriate preventive and corrective measures, ship operators can ensure the effective operation of the OWS, minimize oil pollution, and comply with environmental regulations.