Much like the modules and structures used on oil and gas platforms, or other maritime structures, ballast tanks and the ballast water that fill them, are an integral part of the marine industry. Every element has a role to play. 

Nearly every industrial ship and vessel use ballasts to ensure stability and seaworthiness. However, with every advancement, unintended consequences must be addressed. This blog post explores what ballast tanks and ballast water are. We'll also cover the types of vessels that use them, the issues that have arisen with ballast water, and the steps to address issues.

What is a Ballast Tank and Ballast Water?

Ballast has been used on ships dating back to the earliest sea-going vessels. Back then, various types of material, sandbags, rocks, iron blocks, etc., were used to add weight to the ship, improving its stability and seaworthiness. Depending on the weight of the cargo being transported, this material would be added or removed to achieve the desired stability. Today ballast tanks and ballast water have become the norm in providing for the additional weight. These tanks can have various design characteristics depending on the type of vessel they are in, but all follow the same basic principle. Water is pumped into the ballast tank or pumped out to achieve the desired stability and seaworthiness of the vessel. These tanks allow for control over trim, list, draft (draught), and control buoyancy.

What types of offshore oil and gas facilities and vessels use ballast tanks?

Ballast tanks can be found across various offshore oil and gas facilities and vessels, like:

• Semi-Submersibles
• Spar
• Tension Leg Platforms
• Semi-Submersible Platform
• Floating Production Storage and Offloading
• Drillships
• Offshore wind farms can also use ballasts for offshore wind turbines

Why is ballast water important?

The widespread implementation of ballast tanks and the growth of international shipping has led to vessels filling and dumping ballast water in all parts of the world. This water can contain many organisms native to the ecological system the water is drawn from, including aquatic or marine microbes, plants, and animals. These organisms are introduced into the local ecosystem when the ballast water is dumped. Dumping ballast water may introduce new invasive species, which can devastate the local ecosystem.

What is being done to address ballast water issues?

To address ballast water issues, the International Maritime Organization (IMO) adopted The International Convention for the Control and Management of Ships' Ballast Water and Sediments, also known as the Ballast Water Management Convention, in 2004. The convention's purpose is to prevent the spread of harmful aquatic organisms from one region to another through the dumping of ballast water. Under the convention, ships must implement ballast water management plans and use ballast water treatment systems that the IMO approves. These systems must be capable of achieving a certain level of effectiveness in removing or inactivating harmful aquatic organisms from the ballast water.

The convention became effective on September 8, 2017. As of December 2021, it has been ratified by 88 countries and the European Union. Implementation of the convention is ongoing, and the IMO is working with member countries to support the development and approval of effective ballast water treatment technologies.

Ballast Water Treatment Solutions

There are a few different treatment solutions that use a variety of disinfectants to ensure the ballast water is safe to be dumped from the tanks. Most treatment solutions begin with filtration. As the ballast water is drawn into the tanks, it is passed through a series of filters to remove any solid or suspended particles. This filtration can effectively remove many types of microorganisms, including bacteria and algae, from the water. However, because filtration alone may not be sufficient to remove all harmful species, additional treatment methods must also be implemented. After filtration, the water will then move to a disinfectant tank where the water can be cleaned further in a few different ways.

UV Disinfection:

In this process, ballast water is exposed to intense ultraviolet (UV) light, which can kill or inactivate many types of microorganisms. UV disinfection has several advantages over other methods, including its effectiveness against a wide range of species, its low toxicity, and its ability to leave no harmful byproducts. However, UV disinfection systems can be expensive and require careful maintenance to ensure they are operating at peak efficiency.

Electrolysis:

In this process, ballast water is passed through an electrochemical cell, where it is treated with an electrical current. This current creates a mixture of powerful disinfectants, such as hydrogen peroxide and hypochlorite, which can effectively kill or inactivate many microorganisms. Electrolysis has several advantages, including its effectiveness, low toxicity, and ability to leave no harmful byproducts. However, it can be a complex and costly technology to implement and maintain.

Chemical Disinfection:

Chemicals, such as chlorine or ozone, are introduced into the water and kill or inactivate a wide range of harmful microorganisms. Chemical disinfection requires additional steps before the water can be dumped. A neutralization process or water quality adjustment during discharge is necessary to address the byproducts of the chemical process and ensure harmful chemicals are not discharged.

Ballast water treatment solutions are an important part of the marine industry. The regulations implemented by the IMO are essential to ensuring the protection of the waters that these vessels travel. If you're interested in learning about the other regulatory bodies that help keep the environment safe, you can read more about offshore classification societies and rule requirements.