Sewage Treatment Plant
Oct 15, 2025



Sewage Treatment Plants Onboard Ships: Keeping Our Oceans Clean

Sewage Treatment Plants (STPs) onboard ships play a crucial role in protecting our oceans from pollution. This article explores their history, purpose, importance, and operation highlighting how modern vessels manage wastewater responsibly to meet international standards and support sustainable maritime practices under MARPOL Annex IV.


Introduction: Why Ships Need Sewage Treatment Plants

Every ship produces sewage from toilets, galleys, and accommodation areas. If discharged untreated, this waste can harm marine life and coastal waters. To prevent pollution, ships are fitted with Sewage Treatment Plants compact systems that treat and disinfect wastewater before release, ensuring compliance with IMO regulations.

Passenger ships and vessels over 400 gross tonnage must be equipped with STPs to safeguard human health and marine ecosystems.

A Brief History of Sewage Treatment at Sea

In the past, ships routinely released raw sewage into the ocean. Growing awareness of pollution’s impact led to international action. The International Maritime Organization (IMO) introduced MARPOL Annex IV in 2003, requiring all ships to properly manage sewage.

Over time, basic holding tanks evolved into modern biological treatment units capable of producing clean effluent. Some nations, like the United States, had already established strict sewage control laws, paving the way for global standards.


Purpose of a Shipboard Sewage Treatment Plant
The main goal of a shipboard STP is to treat and purify wastewater before discharge. It aims to:

•Remove solids and organic matter
•Eliminate harmful bacteria and pathogens
•Reduce odors and contaminants
•Meet MARPOL and flag-state requirements

Treated effluent must meet specific IMO limits on biochemical oxygen demand (BOD), suspended solids, and coliform bacteria before being safely discharged.



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How a Shipboard STP Works
A typical sewage treatment system operates in three main stages:

1. Primary Treatment– Screens and sedimentation separate solids and sludge.
2. Secondary Treatment– Aerobic bacteria break down organic waste in aeration chambers.
3. Tertiary Treatment (Disinfection)– Effluent is disinfected using chlorine, UV light, or ozone, ensuring pathogens are destroyed before discharge.

Some systems also include sludge handling units for safe disposal in port facilities.

Importance of Sewage Treatment Onboard Ships

•Sewage treatment is both an environmental and legal requirement. Its importance includes:

•Preventing marine pollution by reducing harmful discharge

•Protecting crew health by controlling bacteria and odors

•Ensuring legal compliance with MARPOL Annex IV and the International Sewage Pollution Prevention Certificate (ISPPC)

•Supporting sustainability, reflecting the maritime industry’s move toward greener operations


Regulations and Future Developments

MARPOL Annex IV allows discharge of treated sewage only when ships are at least 3 nautical miles from land, or 12 miles for comminuted and disinfected waste. Ships must maintain certified STPs and undergo regular inspection to ensure compliance.

Modern systems are now automated, compact, and energy-efficient. New technologies like membrane bioreactors (MBR), advanced UV disinfection, and digital monitoring aim to achieve zero-discharge or water-recycling operations leading to cleaner, more sustainable shipping.


Summary of the Topic

Though often unseen below deck, Sewage Treatment Plants are essential for keeping oceans clean. By effectively managing wastewater, ships not only meet international standards but also help preserve marine biodiversity and contribute to a healthier, sustainable planet.

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UNDERSTANDING ABOUT ISPS CODE

Introduction The International Ship and Port Facility Security (ISPS) Code is a comprehensive set of measures designed to enhance the security of ships and port facilities. It was adopted by the International Maritime Organization (IMO) under the framework of the International Convention for the Safety of Life at Sea (SOLAS), specifically through an amendment introduced in December 2002. The ISPS Code officially came into force on 1 July 2004, marking a turning point in maritime safety and global security.

JET CHISEL

A jet chisel (also called needle scaler) is a pneumatic tool made up of multiple thin steel rods (“needles”) that rapidly move back and forth when connected to compressed air. The vibration of the needles chips away rust, old paint, scale, and marine growth on metal surfaces. Think of it as “pangbaklas ng kalawang, pero industrial version.” Purpose: • Remove rust, corrosion, and scale from steel surfaces • Prepare metal before painting, welding, or coating • Clean areas where grinders and wire brushes can’t reach (corners, tight spots, edges) • Reduce manual scraping time and physical fatigue How to Use: 1. PPE First • Safety goggles / face shield • Ear protection (maingay ’yan) • Gloves • Mask (dust/rust particles) • Proper coverall 2. Check the Tool • Inspect air hose, connectors, and needles • Ensure air compressor pressure is within recommended range (usually 90 psi ± depending on tool) 3. Connect to Compressed Air • Attach hose firmly • Open the air valve gradually 4. Operate • Hold the tool with both hands • Press the needles gently against the surface — do not push too hard • Let the vibration do the work • Work in steady strokes 5. After Use • Shut off air supply • Clean and oil the needles to prevent rust • Store in dry location

PARTS OF A SHIP

Front (Bow) Area Bulbous Bow A rounded projection located below the waterline at the forward part of the hull. It reduces wave resistance and helps improve the ship’s fuel efficiency and stability. Bow The forward-most section of the ship designed to cut through the water as the vessel moves. Stem The vertical front edge of the bow that forms the main support where the two sides of the hull meet. Foredeck The deck area located at the forward part of the ship, often used for anchor handling and mooring operations. Fore Mast A mast positioned near the bow used to mount lights, radar, antennas, and other navigational instruments. Hatch Cover A watertight cover placed over cargo holds to protect the cargo from seawater and weather exposure. Deck The main working platform of the ship where crew activities and operations take place. Hull The main outer structure or body of the ship that provides buoyancy and keeps the vessel afloat. Anchor A heavy device lowered to the seabed to hold the ship in position and prevent drifting. Bridge The command center of the ship where navigation, control, and monitoring of vessel movement and operations are performed. Midship and Superstructure Superstructure The portion of the ship constructed above the main deck, housing key operational and living spaces. Accommodation The area where the crew lives and works. It includes cabins, mess rooms, offices, and other essential living facilities. Flying Bridge / Bridge Wings Side platforms extending from the bridge used for maneuvering and observation, especially during docking and unmooring. Monkey Island An open platform located above the bridge that provides access to radar, communication, and navigation equipment, as well as offering an unobstructed view of the surroundings. Main Mast The primary mast supporting communication systems, navigation lights, and other electronic devices.

The Four Pillars of the International Maritime Organization (IMO)

The International Maritime Organization (IMO) establishes global standards to promote safety, protect the marine environment, ensure proper training of seafarers, and safeguard their welfare. These standards are anchored on four key conventions known as the 4 Pillars of IMO: 1. SOLAS – Safety of Life at Sea (1974) SOLAS is considered the most important international treaty concerning maritime safety. It sets the minimum standards for the construction, equipment, and operation of ships to ensure they are safe for both crew and passengers. This includes: • Fire protection systems • Life-saving appliances • Navigation and communication requirements • Emergency preparedness Its ultimate purpose is to prevent loss of lives at sea. 2. MARPOL – Marine Pollution (1973/1978) MARPOL addresses the prevention of pollution from ships. It regulates: • Oil and chemical spills • Sewage and garbage discharge • Air emissions from ships Its goal is to protect the marine and coastal environment by minimizing pollution from ship operations and accidents. 3. STCW – Standards of Training, Certification, and Watchkeeping for Seafarers (1978) STCW sets global training and competency standards for seafarers working on commercial vessels. It ensures: • Seafarers are properly trained, qualified, and certified • Uniform watchkeeping and operational safety practices across the world This helps maintain a high level of professionalism and safety at sea. 4. MLC – Maritime Labour Convention (2006) The MLC is often called the “Seafarers’ Bill of Rights.” It ensures that seafarers have: • Fair wages and employment contracts • Safe working and living conditions • Adequate rest hours • Medical care, social protection, and welfare The convention promotes human rights and dignity for those working at sea.

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