Bilge Dumping: From Ships Contaminate Oceans

by | Feb 17, 2023 | Pollution, Trending, Water Pollution

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What Is Bilge Dumping?

Bilge dumping is when ships intentionally release untreated or poorly treated wastewater into oceans. It is a ship’s discharge of sewage into coastal and ocean waters. Which can include both polluted water (black water) and untreated water (gray water). It contains chemicals, oils, and other contaminants. The wastewater can come from a ship’s bilge (the area in a ship designated for waste and water accumulation), engine, toilets, laundry, or other places on board with water present. Bilge dumping from ships contaminates oceans.

The bilge is the lowest part of a ship. Bilge waters are a mix of potentially toxic waters. They can contain a mixture of detergent, oil, water, gasoline, human waste, and other chemicals. They may also sometimes have lead and arsenic. Bilge water usually forms in container and cargo vessels because of their heavy oil use. Their use of oil produces thick, oily sludge. This sludge travels and accumulates at the bottom of the ship. The sludge requires regular drainage. One cargo ship can produce several tons of bilge water daily.

FILE - This aerial view shows a boat leaking oil in the waters near Rio de Janeiro, Brazil. In Seattle, a jury convicted a fisherman of similarly dumping oily pollution into the Pacific Ocean.


Because it typically occurs far out at sea, bilge dumping has stayed hidden for decades. International laws specify how ships should treat bilge water to protect marine ecosystems. However, SkyTruth discovered that many ships simply dump bilge water directly into the ocean. SkyTruth is an environmental conservation organization that uses satellite imagery to expose environmental crimes. It also discovered that ships routinely get away with dumping wastewater into the seas. Ships dump them in the ocean untreated to escape the operational cost of treating bilge. European waters report up to 3,000 cases of bilge dumping every year. These are only the ones reported. There could be higher incidences of bilge dumping actually happening. A large ship can accumulate up to 8 metric tons of bilge water every day.

Decades ago, international law banned the dumping of oil wastewater into oceans. But, ships use various methods to bypass international water pollution laws, threatening marine life and ecosystems.

In 2021, SkyTruth hundreds of potential dump sites across the globe’s oceans. However, this number could be much higher since SkyTruth’s satellites cover less than one-fifth of the planet’s seas. SkyTruth’s report indicates that ships could be dumping around 52.8 gallons of bilge water into the ocean every year.

When bilge spills travel to beaches and coastal areas, it severely affects tourism and fishing. Many fisher folks lose their livelihood for days due to bilge dumping.

Slow Action Against Bilge Dumping

Even with sophisticated technology that can easily and quickly identify oil spills, countries have been extremely slow in taking action against perpetrators. This led to a culture of impunity.


The European Maritime Safety Agency (EMSA) uses satellite images to identify potential oil discharges from ships. Once they notice a spill, they alert the relevant EU country. The particular country is supposed to immediately inspect the site and report its findings to EMSA. However, the organization revealed that governments have been providing it with feedback. Out of the 7,672 oil spills the agency detected, it received governmental feedback for only a third. The longer a country takes to inspect a detection, the higher the chances are that it will report back ‘nothing observed.’

There is another challenge in getting governments to persecute ships discharging bilge waters. Even when countries identify cases of illegal bilge dumping, nothing binds them to report the action they’ve taken against the perpetrators. Even if governments have the best tools in the world, we cannot fix the problem without public accountability and pressure.

Hefty fines await merchant ships that illegally dump bilge water. In 2016, a 40 million dollar fine was slapped on Carnival’s Princess Cruises for illegally dumping bilge water along the British coast.

Ships have developed several tactics to avoid getting caught by authorities. They usually dump bilge water at night or on rough seas. It is challenging to detect bilge in rough seas.

Effects on Marine Life

Bilge dumping from ships contaminates oceans and the life it harbors. Bilge is extremely dangerous to fish, marine wildlife, humans, and the water itself. It introduces toxicity to the ocean and increases the concentration of pollutants.

Free photos of Fish

Bilge has a range of negative impacts on marine life and ecosystems. The two significant impacts are:

1. Killing or harming marine species

Oil fouls the feathers of marine birds. This makes them lose the ability to insulate themselves. It makes them more vulnerable during the cold weather. Oil also clogs the gills of fish and makes it harder for them to breathe.

2. Water Pollution

Bilge dumping, without a doubt, increases pollution levels in the ocean. Due to this, dead zones in the ocean form. Dead zones are areas in oceans that do not contain enough oxygen to support marine life.

A 2016 study found that oil spills can cause a decline in plankton populations in the sea. Bilge can directly cause toxic effects in the smallest of marine creatures. Its consequences can travel all the way up the food chain.

What Can Ships And The General Public Do To Stop Bilge Dumping?

Ships must have proper wastewater treatment systems on board so that they can treat bilge before releasing it into the ocean. Ships can even have extra tanks to store bilge water until they can properly dispose of it.

Regularly cleaning and maintaining the bilge area of ships will ensure that the waters that collect there have low levels of pollutants and contaminants.

Additionally, governments must develop quick response and management measures to tackle illegal bilge dumping. They must prosecute perpetrators and bring environmental justice. They can even designate spaces where ships can safely discharge bilge waters, thus protecting marine environments.

You, as an individual, can help fight bilge dumping by supporting organizations that work toward stopping this destructive practice. You can educate yourself and others about why bilge dumping is wrong. Increased public awareness will pressure governments to actually do something and fine ship owners that dump bilge into the ocean. It can also lead governments to establish strict laws that ban bilge dumping and introduce jail time for bilge dumpers.



  • Dr. Emily Greenfield

    Dr. Emily Greenfield is a highly accomplished environmentalist with over 30 years of experience in writing, reviewing, and publishing content on various environmental topics. Hailing from the United States, she has dedicated her career to raising awareness about environmental issues and promoting sustainable practices.

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  1. Pedro Porcino



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