Ballast water is water that is taken on board a ship to maintain its stability and balance. It is usually discharged at the destination port, where it can introduce invasive species and pathogens that can harm the local marine ecosystem. To prevent this, ballast water treatment systems (BWTS) are used to disinfect and filter the water before it is released.
UV-Based and Electro chlorination Ballast Water Treatment Systems
There are different types of Ballast Water Treatment Systems, but two of the most common ones are based on ultraviolet (UV) radiation and electro chlorination (EC). In this post, we will compare these two methods and discuss their advantages and disadvantages.
UV-based BWTS use high-intensity UV lamps to kill or damage the DNA of microorganisms in the ballast water. This prevents them from reproducing and causing harm. UV-based BWTS are effective against a wide range of organisms, including bacteria, viruses, algae, and zooplankton. They do not produce any harmful by-products or residuals that need to be neutralized or disposed of. They also do not affect the salinity, pH, or temperature of the water.
However, UV-based BWTS also have some limitations. They require a lot of electrical power to operate the lamps, which can increase the fuel consumption and emissions of the ship. They also depend on the clarity and quality of the water, as turbid or colored water can reduce the penetration and effectiveness of the UV rays. Moreover, some organisms may have natural resistance or repair mechanisms that can allow them to survive the UV exposure.
EC-based Ballast Water Treatment Systems use electricity to convert seawater into a dilute solution of sodium hypochlorite (NaClO), which is a powerful disinfectant. The NaClO solution is injected into the ballast water, where it kills or inactivates the microorganisms. EC-based BWTS are effective against most organisms, including bacteria, viruses, algae, zooplankton, and larger organisms such as mussels and barnacles. They also work well in turbid or colored water, as they do not rely on light transmission.
However, EC-based BWTS also have some drawbacks. They produce chlorine gas as a by-product, which can be hazardous to human health and the environment if not properly vented or contained. They also generate other by-products such as bromate and trihalomethanes, which are potentially carcinogenic and toxic to aquatic life. These by-products need to be monitored and controlled to meet the regulatory standards and guidelines. Additionally, EC-based BWTS affect the salinity, pH, and temperature of the water, which can have negative impacts on the corrosion and scaling of the ship’s pipes and tanks.
As we can see, both UV-based and EC-based BWTS have their pros and cons, and there is no clear winner or loser in this comparison. The choice of the best method depends on various factors such as the type and size of the ship, the route and destination of the voyage, the availability and cost of electricity, the quality and quantity of the ballast water, and the environmental and safety regulations. Therefore, ship owners and operators need to carefully evaluate their options and select the most suitable BWTS for their specific needs.
