*2.5.4. Equipment*

The system consists of a combination of oxygen supply and high power electric supply systems: a high voltage electric current flow between electrodes and oxygen is discharged between the electrodes. Electrodes are separated with the help of a dielectric gap that contains the discharge chamber for oxygen flow. Electric field causes the breakdown of oxygen molecules and formation of ozone occurs. After generation, the ozone is directed toward the connection chamber, where the treated water is to be disinfected. The ozone produced will dissociate immediately so onsite generation of ozone must be done.

One of the important features is the contact time as well. So, the ballasting and the deballasting modes of very large ballast amounts of water will be much expensive in full-scale applications. One or several ballast water are equipped with ozone injection equipments that act as contact chambers. For achieving long contact time, that ballast water should be pumped into these contact tanks. In order to reduce the sediment formation and fine particles to enter the treatment process, the ozone treatment must undergo preliminary treatment (filter or cyclone).

The ballast treatment ensures that the all the water present in ballast tanks is exposed to ozone at the beginning of the voyage. Contact time plays an important role in the disinfection process. Disinfection is ensured if long contact is not required against the specific microorganism. If long contact time is required against specific microorganisms, treatment should be done during voyage to enable longer contact times.

Organic carbons are associated with sediment formation. These sediments settle down at the bottom of the ballast tanks during voyage. The sediments contain the microbes that are difficult to treat like bacterial colonies or viral clumps. Ozone treatment might not be efficient in the sediment. Ammonia might be produced as a result of biological activity during voyage. Bromines are produced by the reaction of ammonia and disinfectant residual. Bromines are weaker disinfectants, thus the efficacy is reduced [14].
