Filter plants in the ballast water filtration workshop are displayed.

IMO Approved Ballast Water Treatment Standards & Solutions

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Industry Background

The discharge of untreated ship ballast water will cause pollution to the environment while harmful aquatic organisms from the ballast water may pose a threat to human health. The risk of introducing harmful aquatic organisms, pathogens and associated sediments from ship's ballast water should be minimized. Therefore, the International Maritime Organization (IMO) formulated the International Convention for the Control and Management of Ship's Ballast Water and Sediments in 2004. The filtered ballast water shall conform to IMO standards.

All ships adopting ballast water exchange shall comply with the following requirements:

Where possible, ballast water exchange shall be carried out at least 200 nautical miles away from the nearest land and in water at least 200 meters in depth, considering the guidelines developed by IMO.
In cases where the ship cannot conduct ballast water exchange as mentioned above, the ballast water shall be discharged as far away from the nearest land as possible and in all cases at least 50 nautical miles from the nearest land and in water at least 200 meters in depth.
When these requirements cannot be met, areas may be designated where ships can conduct ballast water exchange. All ships shall remove and dispose of sediments from spaces designated to carry ballast water in accordance with the provisions of the ship's ballast water management plan (Regulation B-4).

Methods of ballast water exchange

Sequential exchange method. Ballast tank discharges ballast water first, and then is refilled with clean water. In this method, all previous ballast water shall be pumped out until suction disappears and then filling shall be commenced.
Flow-through method. Ballast tank discharges ballast water and is refilled simultaneously by pumping in clean water. In this method, the tank is overflowed through air pipes. In this method, at least three times the tank volume shall be pumped through the tank.

Solution

IMO approved ballast water treatment system

The treatment process of ballast water management system (BWMS) mainly consists of three procedures: filtration, disinfection and neutralization.

Ballast water treatment process
Filter Unit

Ballast water is filtered through an automatic backwash filter with a 50 μm screen to remove marine organism larger than 50 μm and send them back to the local water. When particles and organics block the filter, the device detects an increase in the pressure difference and blows them off automatically.

Ballast water filter with adaptive filter elements

Ballast water filter with automatic self-clean backwashing functions

Filter elements (fixed or removable) and filter discs can effectively remove suspended solids from ballast water by performing automatic backwashing, therefore, they are widely used in ballast water filtration. They are very environmentally friendly as they do not use toxic chemicals in ballast water. Screen filtration is effective for removing larger suspended solids. However, it is less effective in removing small particles and organisms.

Stainless steel filter discs

Stainless steel filter elements
Disinfection System

Seawater electro-chlorination disinfection equipment and UV disinfection devices are employed for the disinfection system.

Seawater electro-chlorination disinfection system

UV disinfection device
- Seawater Electro-Chlorination Disinfection
  
  A small amount of filtered seawater flows into the electrolysis device to produce high concentrated sodium hypochlorite solution. The solution will be then injected into the main ballast pipe line after degas treatment. The sodium hypochlorite solution will be mixed with the seawater in the main ballast tube to a certain designed concentration that can kill marine organisms in the water, including spores, lava and pathogens, to meet the disinfection standard (D-2 standard and others). The concentration of the mixed solution in the main pipeline is monitored and controlled by the TRO unit and the main control unit of the system.
- Ultraviolet Disinfection Units
  
  It is equipped with high-density, medium-pressure ultraviolet (MPUV) lamps that can destroy the reproductive cells of living organisms in ballast water, thereby preventing the organisms from reproducing and colonizing. Each UV lamp is located in a quartz sleeve with watertight seals to avoid direct contact with water. The UV chamber is equipped with a UV intensity sensor to ensure that the required UV dose can be applied regardless of the operating conditions.
Neutralization Unit

When the TRO concentration of the ballast water to be discharged is lower than the value specified by IMO, the neutralization unit will not work and discharge ballast water outboard directly. When the TRO concentration of the ballast water to be discharged is higher than the value specified by IMO, the neutralization unit will start automatically and inject neutralizers to eliminate and neutralize the residual TRO. The while process of neutralization is automatically controlled by the neutralization unit.

Neutralization unit control panel

Neutralization unit