The ballast water treatment & management system (BWTS) is designed to remove harmful organisms that enter ships through ballast tanks. It uses chemicals to kill these organisms before they reach other parts of the ship. Ships use ballast tanks to balance out the weight of cargo when travelling between ports. These tanks are filled with seawater during transit. However, some of the water in the tanks contains organisms that can harm marine life. This is called “ballast water.” A major problem for the shipping industry is invasive aquatic species in ship's ballast water. The implementation of a ballast water management plan and ballast water treatment system became mandatory after the International Convention for the Control and Management for ship, ballast water and sediments came into effect. These are some of the Ballast water treatment methods used commonly:
Ship ballasting
A number of shipping operators have begun installing ballast water treatment systems on their ships in order to comply with the IMO's rules and regulations regarding ballast water management. There are a variety of technologies on the market for treating ballast water on ships. However, constraints such as space availability, cost of implementation, and level of environmental friendliness play an important role in the selection of a particular type of ballast water treatment & management system. The choice of a ballast water treatment system for a ship is influenced by a number of factors. They could be one of these:
Effectiveness on ballast water organisms
Environment-friendliness
Safety of the crew
Cost-effectiveness
Ease of installation and operation
Space availability on board
In the market, there are four main types of ballast water treatment technologies:
Filtration Systems (physical)
Chemical Disinfection ( oxidizing and non-oxidizing biocides)
Ultra-violet treatment
Deoxygenation treatment
Heat (thermal treatment)
Acoustic (cavitation treatment)
Electric pulse/pulse plasma systems
Magnetic Field Treatment
For ballast water treatment on board ships to meet IMO standards, two or more technologies are typically combined.
Physical Separation/ Filtration Systems Ballast Water Treatments
In sedimentation or surface filtration systems, marine organisms and suspended solids are separated from the ballast water by physical separation. As a result of the filtration process, suspended/filtered solids and wastewater (backwashing) are either discharged in the area from where ballast is taken or are further processed onboard ships before they are discharged. These are some of the Physical Water treatment process used in Ship Ballasting:
Screens/ Discs
With automatic backwashing, screens (fixed or movable) or discs are used for the effective removal of suspended solid particles from ballast water. They are extremely eco-friendly, as they do not require the use of toxic chemicals in the ballast water. Screen filtration is effective for removing larger particles of suspended solids but is not very useful for removing smaller particles or organisms. The use of screens is highly effective in removing the majority of suspended particles and organisms from ballast water, but it is not sufficient to treat the ballast water according to the IMO standards.
Hydrocyclone
Ballast water can be effectively separated from suspended solids with the help of a hydro-cyclone. In order to separate solids from water, high-velocity centrifugal force is applied. Hydrocyclones have no moving parts, which makes them easy to install, operate, and maintain onboard ships. Note: It has been found that as the operation of hydro cyclones heavily depends on the mass and density of the particle, they are not successful in removing smaller organisms from the ballast water.
Coagulation
The process of coagulation is used to join smaller particles together in order to increase their size prior to filtration since most physical filtration methods cannot remove smaller solid particles. In the above-mentioned filtration processes, efficiency increases with the size of the particles. The process of coagulating smaller particles into small flocs is called flocculation. The flocs settle more quickly and can be easily removed. Note: Some ballast water treatment systems use ancillary powders (sand, magnetite, etc.) or coarse filters to produce flocs. Ships need additional space on board to accommodate the additional tank for treating ballast water for this process.
Media Filters
Media filters can be used efficiently to filter out smaller particles and organisms from the ballast water. The compact size and lower density of compressed media filters (Crumb rubber) make them well suited to shipboard use over conventional granular filtration systems.
Magnetic Field Treatment
The magnetic field treatment uses coagulation technology. Ballast water is mixed with magnetic powder and coagulants. This leads to the creation of magnetic flocs, which include marine organisms. Magnetic flocks are separated from water using Magnetic Discs. Ballast water treatments with chemical disinfectants. (oxidizing and non-oxidizing biocides) Marine organisms in the ballast water can be removed or inactivated with the help of marine organisms. Nonetheless, the biocides used to disinfect ballast water must be effective against marine organisms as well as readily degradable or removable so that the discharge water is prevented from becoming toxic in nature. Biocides are classified into two types based on their functionality:
Oxidizing
Non-Oxidizing
Oxidizing biocides
Oxidizing biocides are general disinfectants used to kill organisms in ballast water. Examples include chlorine, bromine, and iodine. Disinfectants of this type destroy the organic structures of microorganisms, such as their cell membranes and nucleic acids.
Non-oxidizing biocides
There are several non-oxidizing biocides on the market, but only a few are used in ballast water treatment systems as they tend to produce toxic by-products. Researchers in this field are working hard to find non-oxidizing biocides that can be used in ballast treatment plants. Non-oxidizing biocides are disinfectants that interfere with the reproductive, neural, or metabolic functions of organisms. Information on biocides can be found below; A few of the processes utilizing oxidizing biocides used onboard ships are: Chlorination- Micro-organisms are destroyed in water when chlorine is diluted into it. Ozonation- An ozone generator is used to produce ozone gas which is bubbled into the ballast water. In water, ozone decomposes and reacts with other chemicals to kill organisms.
Ultra-Violet Treatment Method
UV lamps surround a chamber through which ballast water passes in order to treat ballast water. UV lamps (Amalgam lamps) produce ultraviolet rays which act on the DNA of the organisms and cause them to cease reproducing. A wide range of organisms has been successfully removed from water using this method.
Deoxygenation
As the name suggests, the deoxygenation ballast treatment method involves purging/removing oxygen from the ballast water tanks to make the organisms asphyxiate. Usually, this is accomplished by injecting nitrogen or any other inert gas above the level of the water in the ballast tank. The organisms are asphyxiated by the inert gas in about 2-4 days. Thus, this method is not suitable for ships with short transit times. In addition, ships with completely sealed ballast tanks are appropriate for using such systems.
Heat Treatment
The ballast water is heated to certain temperatures that will kill the organisms in this mode of treatment. The ballast water can be heated by a separate heating system or can be used to cool the ship's engine, thus disinfecting the organisms from the heat acquired from the engine. These treatments are more time-consuming and likely to increase tank corrosion.
Cavitation or Ultrasonic Treatment
High-energy ultrasound is used to kill the organisms in ballast water using ultrasonic energy. In general, high-pressure ballast water cavitation techniques are used in conjunction with other systems.
Electric Pulse / Plasma Treatment
Ballast water treatment by electric pulse/plasma is still in the development phase. Short bursts of energy are used in this system to kill organisms in ballast water. The pulsed electric field technology uses two metal electrodes to produce very high power density and pressure energy pulses in ballast water. Organisms are killed by the energy produced. Generating a plasma arc with a high energy supply through electric plasma technology kills the organisms present in the ballast water. Both methods are said to have almost the same effect on organisms.
Treatment System for Ballast Water on Ships
Ballast water treatment & management systems typically use a combination of 2-3 disinfectant methods in different stages. Ballast water treatment plants typically consist of two stages. The first stage employs physical separation, while the second uses some type of disinfectant. The combination of treatment systems used in a ship depends on a variety of factors, such as the type of ship, the amount of space available on the ship, and the cost limitations discussed earlier. Maritronics is the ballast water management system in Dubai.
Conclusion
There is a spike in the increase of the latest technology for the ballast water on board ships in the market. Reach us for the best ballast water treatment systems from the market.
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