Hotel Service Unit 10 Q1

MARPOL currently has six Annexes, each addressing a specific type of marine pollution:  

1. MARPOL – dco.uscg.mil – Coast Guard

• Annex I: Prevention of Pollution by Oil   1. International Convention for the Prevention of Pollution from Ships (MARPOL) www.imo.org
• Annex II: Control of Pollution by Noxious Liquid Substances in Bulk   1. Carriage of chemicals by ship – International Maritime Organization www.imo.org
• Annex III: Prevention of Pollution by Harmful Substances Carried by Sea in Packaged Form   1. studylib.net studylib.net2. International Convention for the Prevention of Pollution from Ships (MARPOL) www.imo.org
• Annex IV: Prevention of Pollution by Sewage from Ships   1. Prevention of Pollution by Sewage from Ships – International Maritime Organization www.imo.org
• Annex V: Prevention of Pollution by Garbage from Ships   1. Prevention of Pollution by Garbage from Ships – International Maritime Organization www.imo.org
• Annex VI: Prevention of Air Pollution from Ships   1. MARPOL Annex VI and the Act To Prevent Pollution From Ships (APPS) | US EPA www.epa.gov2. www.lr.org www.lr.org

These Annexes outline specific regulations and requirements for ships to minimize their environmental impact and protect the marine environment.  

1. MARPOL 73/78 – Wikipedia

According to MARPOL Annex IV, the rules for discharging untreated sewage are as follows:

General Rule: Discharge of untreated sewage is prohibited.

Exceptions:

• Distance from Land: Untreated sewage may only be discharged when the ship is more than 12 nautical miles from the nearest land.
• Discharge Rate: Even when beyond 12 nautical miles, the discharge of untreated sewage from holding tanks must not be instantaneous. It should be discharged at a moderate rate while the ship is en route and proceeding at a speed of not less than 4 knots. The specific discharge rate may be subject to further guidelines or approvals from the Administration.

Additional Considerations:

• Special Areas: Special Areas, such as the Baltic Sea, may have even stricter regulations on sewage discharge, including a complete ban on untreated sewage discharge regardless of the distance from land.
• Comminuted and Disinfected Sewage: Sewage that has undergone comminution (breaking down into smaller particles) and disinfection may be discharged closer to land, typically at a distance of more than 3 nautical miles. However, this requires the use of an approved system.

Rationale behind the rules:

• Natural Breakdown: The basic principle is that on the high seas, the oceans are capable of naturally assimilating and breaking down raw sewage through bacterial action. However, closer to land, the potential impact on coastal ecosystems and human health is higher, hence the stricter restrictions.
• Protecting Coastal Areas: By prohibiting or limiting untreated sewage discharge near land, MARPOL Annex IV aims to safeguard the water quality of coastal areas, protect marine life, and prevent health risks to humans who use these waters for recreation or fishing.

Remember:

• It is essential for ships to comply with these regulations to minimize the environmental impact of sewage discharge and contribute to a cleaner and healthier marine environment.
• Non-compliance can result in penalties and enforcement action by port state control authorities.

If you would like, you can ask me about the rules for discharging treated sewage or other aspects of MARPOL Annex IV.

According to MARPOL Annex IV, the rules for discharging comminuted and disinfected sewage are:

Discharge is permitted when:

• Distance from Land: The ship is at least 3 nautical miles from the nearest land.
• Approved System: The sewage has been treated using a sewage comminuting and disinfecting system approved by the Administration.
• No Visible Solids or Discoloration: The effluent (treated sewage) must not produce visible floating solids or cause discoloration of the surrounding water.

Key Points:

• Comminution: This process involves breaking down the sewage into smaller particles, typically through grinding or maceration.
• Disinfection: This process involves treating the sewage to reduce or eliminate harmful bacteria and other pathogens, usually through chlorination or UV radiation.
• Holding Tank Requirement: Even with an approved comminuting and disinfecting system, ships must still have a sewage holding tank for storing sewage when within 3 nautical miles of land.

Rationale behind the rules:

• Reduced Environmental Impact: Comminution and disinfection significantly reduce the environmental impact of sewage discharge compared to untreated sewage. Smaller particles are more easily broken down by natural processes, and disinfection minimizes the risk of spreading pathogens.
• Protection of Coastal Waters: By allowing discharge further from land, the potential impact on coastal ecosystems and human health is reduced.

Exceptions:

• Special Areas: Special Areas, such as the Baltic Sea, may have stricter regulations on sewage discharge, even for comminuted and disinfected sewage.
• Safety and Emergencies: Discharge of sewage may be permitted in situations where it’s necessary for the safety of the ship or saving lives at sea.

Remember: It’s crucial for ships to comply with these regulations to minimize the environmental impact of sewage discharge and contribute to maintaining clean and healthy marine environments. Non-compliance can result in penalties and enforcement action by port state control authorities.

The final discharge from an approved sewage treatment plant is chlorinated before discharge primarily for disinfection purposes.

1. Wastewater Chlorination: Everything You Need To Know – Sensorex Liquid Analysis Technology

Chlorination effectively kills or inactivates a wide range of harmful pathogens, such as bacteria, viruses, and protozoa, that may still be present in the treated sewage. This disinfection process significantly reduces the risk of spreading waterborne diseases and protects the environment and public health.  

1. Wastewater Chlorination: Everything You Need To Know – Sensorex Liquid Analysis Technology

2. Why is Chlorine used in the treatment of Sewage – Netsol Water

Here’s a breakdown of the reasons:

1. Public Health Protection:

• Preventing Waterborne Diseases: Discharging untreated or inadequately disinfected sewage into the environment can contaminate water bodies and pose a serious health risk to people who may come into contact with the water, either directly or indirectly through the consumption of contaminated seafood. Chlorination helps eliminate harmful pathogens and safeguards public health.   1. Wastewater Chlorination: Everything You Need To Know – Sensorex Liquid Analysis Technology sensorex.com
• Protecting Recreational Waters: Coastal areas and waterways are often used for swimming, boating, and other recreational activities. Chlorination of the final effluent ensures that these waters remain safe for public use.   1. Chlorinated Water in Wastewater Treatment – HAOSH haoshpumps.com

2. Environmental Protection:

• Safeguarding Aquatic Ecosystems: Untreated sewage can introduce excessive nutrients and organic matter into the environment, leading to eutrophication, oxygen depletion, and harm to aquatic life. Chlorination helps reduce the biological oxygen demand (BOD) of the effluent, minimizing its impact on the ecosystem.   1. New study finds that sewage release is worse for rivers than agriculture | University of Oxford www.ox.ac.uk
• Preventing the Spread of Disease: Discharging untreated sewage can spread diseases to marine life, potentially causing fish kills or other ecological disruptions. Disinfection through chlorination helps mitigate this risk.   1. Sewage is more than meets the eye – Marine Conservation Society www.mcsuk.org2. Why is Chlorine used in the treatment of Sewage – Netsol Water www.netsolwater.com

3. Compliance with Regulations:

• MARPOL Annex IV: The International Convention for the Prevention of Pollution from Ships (MARPOL) Annex IV sets standards for sewage discharges from ships. In certain cases, it requires the use of approved sewage treatment plants and disinfection, often through chlorination, before discharge.   1. Prevention of Pollution by Sewage from Ships – International Maritime Organization www.imo.org
• Local Regulations: Many coastal states and port authorities have their own regulations regarding sewage discharge, often requiring disinfection to protect local water quality and public health.

While chlorination is an effective disinfection method, it’s important to note that it can also have some potential drawbacks, such as the formation of disinfection byproducts (DBPs) which can be harmful to aquatic life. Therefore, proper dosing and control of chlorine levels are essential to ensure effective disinfection while minimizing any adverse environmental impacts.  

1. Disinfection and Disinfection Byproducts – MN Dept. of Health

Chlorination of sewage effluent is a crucial step in the treatment process, ensuring the removal of harmful pathogens and protecting public health and the environment. Here’s how it’s typically carried out and monitored:  

1. Main steps in the secondary wastewater treatment process – Blog – Fehr Graham

Chlorination Process:

1. Chlorine Dosage:

• Chlorine is added to the treated sewage effluent in the form of:
  • Chlorine gas: Stored in cylinders and injected using a gas chlorinator.   1. Chlorine Gas Injection – Safe Design Practice | Automated Aquatics automatedaquatics.com
  • Sodium hypochlorite (liquid bleach): A more common option for smaller treatment plants, dosed using a chemical metering pump.

2. Contact Time:

• The chlorinated effluent is held in a contact tank or chamber for a specific period, allowing sufficient time for the chlorine to react with and inactivate the microorganisms.   1. What is Chlorination and purpose of chlorination in the STP Plant – Netsol Water www.netsolwater.com
• The required contact time depends on factors like chlorine concentration, water temperature, pH, and the types of pathogens present.   1. What is Chlorination? – Safe Drinking Water Foundation www.safewater.org

3. Dechlorination (if necessary):

• In some cases, excess chlorine may need to be removed from the effluent before discharge to prevent harm to aquatic life.   1. Wastewater Technology Fact Sheet Chlorine Disinfection – epa nepis nepis.epa.gov
• Dechlorination can be achieved using chemicals like sodium thiosulfate or sulfur dioxide, or by using activated carbon filters.

Monitoring and Control:

• Chlorine Residual Measurement:
  • The concentration of residual chlorine in the effluent is continuously monitored using online analyzers or periodic grab sampling and laboratory testing.   1. The Pros and Cons of Continuous Residual Chlorine Monitoring Systems – BOQU www.boquinstrument.com
  • This ensures that the chlorine dosage is adequate for disinfection while remaining within safe limits for discharge.   1. Online Instrumentation for Chlorine Disinfection Control in Wastewater – YSI www.ysi.com
• Flow Rate Monitoring:
  • The flow rate of the effluent is monitored to ensure consistent chlorine contact time and prevent over- or under-dosing.   1. The Importance of Flow Monitoring in the World of Wastewater Treatment valve-world-americas.com
• pH Monitoring:
  • The pH of the effluent is also monitored, as it affects the effectiveness of chlorination. Adjustments may be needed to maintain the optimal pH range for disinfection.   1. Evaluation of chlorination efficiency on improving microbiological and physicochemical parameters in water samples available in Sheble Berenta district Amhara region, Ethiopia – SpringerLink link.springer.com2. pH Control: A Must for Wastewater Treatment Plants – Clean Tech Water www.cleantechwater.co.in
• Alarm Systems:
  • Alarms are typically installed to alert operators of any deviations from set points, low chlorine residual, or equipment malfunctions.
• Automatic Control Systems:
  • Many modern treatment plants use automated control systems to regulate chlorine dosage based on real-time monitoring data, ensuring consistent and efficient disinfection.

Additional Considerations:

• Safety: Chlorine is a hazardous chemical, so proper handling, storage, and safety protocols must be followed to protect personnel and the environment.   1. Chlorine – CCOHS www.ccohs.ca
• Environmental Impact: While effective for disinfection, chlorination can produce disinfection byproducts (DBPs), which can be harmful to aquatic life. Careful control of chlorine levels and dechlorination (if required) are essential to minimize any negative environmental impacts.   1. Disinfection and Disinfection Byproducts – MN Dept. of Health www.health.state.mn.us
• Alternative Disinfection Methods: In some cases, alternative disinfection methods, such as UV radiation or ozonation, may be used instead of or in combination with chlorination, depending on specific requirements and regulations.

In summary, chlorination is a crucial step in sewage treatment, ensuring the removal of harmful pathogens and protecting public health and the environment. Careful monitoring and control of the chlorination process are essential for achieving effective disinfection while minimizing any potential adverse effects.

The correct chlorine content of the final discharge from an approved sewage treatment plant, as per MARPOL Annex IV, should not exceed 1 mg/litre (1 ppm).

This limit ensures effective disinfection while minimizing the potential harm to aquatic life from residual chlorine.