Ballast Water Treatment System (BWTS)
A ballast water treatment system (BWTS) is designed to remove and eliminate biological organisms (zooplankton, algae, bacteria) from ballast water.
The ballast water treatment system is an increasingly evolving technology, and the number of manufacturers active in this field is increasing. For this reason, there is very limited experience in using this service, and there is no one-size-fits-all service.
Ballast water is a way to introduce non-native marine species. This term refers to fresh or saline water that is stored in ballast tanks and ship cargo holds. These tanks are used to create stability on the ship. When a ship travels uncharted at sea, the cargo it carries is not heavy enough, or the sea weather is turbulent and requires more stability, water is stored in these tanks to increase its weight and make it more stable. Another use of ballast water in a ship is to maintain a stable weight for the ship to sink into the water. Therefore, the air draft decreases and the ship can easily pass under bridges and other structures.
For the smooth movement of the ship on board, it must be in a certain weight range to maintain its stability. When the cargo ship delivers part of its cargo to a port, the ballast water replaces the weight deducted from the ship. If a cargo needs to be added to the ship at the next port, this water is drained so that the ship's weight balance is not disturbed by the load. In this way, ballast water may be discharged and loaded in each port to observe the weight range and this water is a combination of several ports. Ballast water release may bring non-native organisms into the evacuation port. These introduced species or biological invaders are also called exotic species, alien species, and non-native species.
The ballast water treatment system works in two stages:
- Mechanical separation
- Physical or chemical treatment
This process is done by technologies based on Ultra-Violet (UV) and Electro-Chlorination (EC). UV systems use physical ultraviolet light as secondary purification, whereas Electro-Chlorination uses a chemical "active ingredient" to inactivate biological organisms. Both systems typically use filtration as the first phase of mechanical operation.
Electric pumps are usually installed vertically and installed with separate motor priming systems. In close-coupled designs, the rotating part of the pump is mounted on an extended motor shaft. This design creates a problem when the pump needs to be opened, as most of the rotor section must be detached from the pump to provide adequate access.
With owners expecting to shorten port rotation time, the need to insert or remove ballasts from tanks can be a sense of urgency. Container ships are an example. Since the containers on the ship create six heights, the ballast must be done accurately and correctly so that it can leave the port. As a result, ballast pumps have to move a significant volume of seawater.
If the operator states that the ballast tank must be emptied or filled at a certain time, you can divide the ballast volume by the time to get the speed. As time passes and the water tank empties the effective flow rate decreases. This in turn means that the safety margin created by the pump manufacturer is reduced and friction losses in the piping can derail the flow.
Another requirement of these pumps is a priming system with sufficient air management capacity. The pump/priming system must not only deal with the depth of the tanks on the double bottom, but also with the height of the pump above the tank. Air injectors have a limited capacity, so separate actuator motor pumps are required for larger pumps.