The Salty Mariner

How Do Ships Get Rid of Waste?

Understanding Ship Waste Management

Getting rid of waste on a ship is a complex process that requires careful planning and management. Ships generate various types of waste, from sewage to hazardous materials, and managing them effectively is critical to protecting marine environments and complying with strict regulations. The Ship's Engineers are responsible for maintaining and operating the many different aspects of a Ship's Sewage system.

Whether it is a 1000 foot long oil tanker with 20 people on board, or a large cruise ship with 5000 people on board, all ships have machinery to hold and process waste; to include holding tanks, piping, valves, motors & pumps, incinerators, macerators, compactors, and more! Engineers are experts that work hard to maintain these systems properly and ensure that ALL waste (not just sewage) is handled safely and in accordance with the applicable laws. This article will explain a bit about this process and what goes into it, and will serve as a very informative article to shed some light on this aspect of ships!

Types of Waste Generated on Ships

Ships produce a diverse range of waste, each requiring specific handling to meet environmental and legal standards. These include:

Sewage (Black Water): Human waste from toilets, often treated onboard using Marine Sanitation Devices (MSDs).
Gray Water: Wastewater from sinks, showers, and laundries, requiring treatment before discharge.
Solid Waste: Solid waste on ships is ultimately collected in a central location. From there, I have seen this trash separated manually by the ships crew so it can be properly processed.
Regular Trash: Non-recyclable, non-hazardous waste such as packaging or general garbage from crew and passengers.
Oily Waste: "Oily Waste" is oil-contaminated water from engine rooms as well as other collection points about the ship. Oily waste is a special category of waste and the amount of oil waste onboard a ship at any given time is tracked with painstakingly tedious detail in a legal document (the Ship's Oil Record Book). This Oil Record Book is reviewed and signed by the Captain and Chief Engineer and is essentially a ledger of the levels of Oily Waste, Waste Oil, and other carefully monitored fluids onboard the ship. Representatives from regulatory bodies such as the U.S. Coast Guard regularly come onboard vessels and review the Oil Record Book to make sure everything is on the up-and-up. Should there be any discrepancies, the Captain, Chief Engineer, or other ship's officers can be held liable and even sent to prison if there is any wrongdoing uncovered. The reason for such stringent accountability is to prevent ship's from illegally dumping oily waste out in the open ocean, which is highly illegal.
Food Waste: Organic waste from galleys and dining areas.
Hazardous Materials (HazMat): Chemicals, batteries, paints, or medical waste requiring special handling.

International and Regional Regulations

Ship waste disposal is governed by strict regulations to protect marine ecosystems. The International Maritime Organization's MARPOL Convention sets global standards, with key annexes including:

Annex I (Oil): Regulates oily waste discharge and incineration, setting strict limits on oil content in discharged water.
Annex IV (Sewage): Sets rules for sewage treatment and discharge, requiring proper treatment before release.
Annex V (Garbage): Bans plastic disposal and restricts other garbage, including incineration limits.
Annex VI (Air Pollution): Addresses emissions from incinerators and HazMat-related waste.

Sewage and Gray Water Management Systems

Sewage and gray water management is critical for ship hygiene and environmental compliance. Marine Sanitation Devices (MSDs) treat sewage, with two common systems:

Vacuum MSD Systems: Just as the name implies, Vacuum systems use pumps to create a Vacuum (negative pressure) within the Sewage system. This negative pressure is created at the collection tanks down in one of the engineering spaces. Much like the old school bank suction tube systems, when a crew member flushes a toilet, the vacuum in the system pulls the contents of the toilet all the way down to the tank due to the negative pressure (in theory). A lot of times, there may be Vacuum leaks or blockages in the piping system, causing the engineers to have to troubleshoot and repair such issues.
Saltwater Flushing Systems: These use seawater to flush sewage (like a normal household toilet) to treatment or holding tanks, common on older or smaller vessels. They are simpler but consume more water and risk corrosion due to saltwater exposure.

Solid Waste Handling and Disposal

Solid waste, including recyclable plastics and regular trash, requires careful management onboard. The process involves:

Sorting: Separating recyclables from non-recyclable regular trash, ensuring proper disposal methods for each type.
Storage: Using compactors to reduce volume in limited onboard space, with dedicated areas for different waste types.
Disposal: Incinerating permitted waste or offloading at port facilities, following MARPOL regulations.

Oily Waste and Bilge Water Management

Oily waste, primarily bilge water from engine rooms, poses significant environmental risks. Oily water separators (OWS) treat bilge water to reduce oil content to below 15 parts per million (ppm), as required by MARPOL Annex I. Treated water may be discharged at sea if compliant, while untreated waste is stored for port disposal or processed in onboard incinerators.

Food Waste Disposal Methods

Food waste from galleys and dining areas is managed under MARPOL Annex V. Ships use pulpers or grinders to process food waste, which can be discharged at sea if ground to less than 25mm and the ship is over 12 nautical miles from shore. Closer to land, food waste must be stored for port offloading or incinerated in compliant incinerators.

Hazardous Materials Management

Hazardous materials (HazMat), such as chemicals, batteries, paints, and medical waste, require specialized handling. MARPOL Annexes V and VI mandate secure storage in labeled containers to prevent leaks or spills. Crews are trained in safety protocols to handle HazMat, minimizing health and environmental risks.

Waste Disposal: In Port vs. At Sea

Waste management differs significantly between in-port and at-sea scenarios:

In Port: Ships offload waste to reception facilities, which handle sewage, regular trash, solid waste, oily waste, and HazMat. Port-specific regulations and inspections ensure compliance.
At Sea: Ships rely on treatment systems like MSDs for sewage and OWS for oily waste. MARPOL restricts discharges (e.g., no plastics or regular trash at sea, food waste only beyond 12 miles).

Emerging Technologies in Ship Waste Management

Innovative technologies are transforming ship waste management:

Advanced Treatment Systems: Reverse osmosis and membrane bioreactors produce cleaner effluent for safer discharge.
Waste-to-Energy: Modern incinerators convert regular trash and food waste into energy, reducing storage needs.
Digital Monitoring: Waste tracking software streamlines compliance with MARPOL regulations.

Challenges and Solutions

Ship waste management faces several challenges:

Limited Storage: Smaller vessels struggle with space for regular trash and HazMat.
Port Facility Variability: Inconsistent quality or availability of reception facilities complicates offloading.
Crew Training: Ensuring compliance with complex regulations requires ongoing education.

Conclusion

Ships get rid of waste through systems like vacuum Marine Sanitation Devices (MSDs), oily water separators, and MARPOL-compliant incinerators, guided by strict regulations. From managing regular trash to hazardous materials, the maritime industry balances operational needs with environmental responsibility. As technology advances and regulations tighten, sustainable practices are shaping the future of ship waste management.