**2.4. Chloramines**

Chloramines are formed by reacting ammonia with free chlorine. They play an important role in providing residual protection in the distribution system. They are very stable. In comparison to chlorine, fewer halogenated by-products are formed [10].

**Figure 3.** Chlorination by calcium hypochloride method.

### *2.4.1. Advantages*

• Chloramine is more stable but not a strong disinfectant as chlorine, providing long lasting residual disinfectant.

destructor, ozone contact chamber, and generator. UV light or the corona discharge process is used for ozone generation. In contact chamber, ozone is added to water. The main purpose of the destructor is to limit the amount of ozone to be stripped out into the air. Three main processes affect the release of ozone after introducing ozone into water: decomposition, reac-

Disinfection Methods

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http://dx.doi.org/10.5772/intechopen.80999

Ozone is produced from a gas containing oxygen (usually ambient air or pure oxygen). The gas is then passed through an electric field. The air is treated to make sure that it is dry and free from dust impurities. Oxygen is converted to ozone in an electrical field. The ozone is then fed to the contact tank so that ozone is dissolved by water to proceed disinfection process [14].

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

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

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

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

Ozone is produced by applying high voltage electricity to a gap (tube) containing pure oxy-

tion with water impurities, and stripping into the atmosphere [14].

dissociate immediately so onsite generation of ozone must be done.

during voyage to enable longer contact times.

weaker disinfectants, thus the efficacy is reduced [14].

gen or filtered dry air (corona discharge method).

*2.5.3. Process*

*2.5.4. Equipment*

cyclone).

*2.5.5. Chemical*


## *2.4.2. Chloramination equipment*

Equipment for both the production of chloramines and chlorination systems are same. Both chlorine and ammonia might be introduced as a liquid or gas. Additionally, both chlorine and ammonia are available in liquid or granular form. Great care must be taken so that concentrated chlorine and ammonia are never mixed as they will form nitrogen trichloride, a potentially explosive compound [11].

### **2.5. Ozonation**

Ozone is an allotropic (unstable) formula of oxygen in which three molecules are combined to produce a new molecule. It quickly decomposes to generate highly reactive free radicals. The ozone's oxidation potential (−2.7 V) is greater than that of the chlorine (−1.36 V) or hypochlorite ion (−1.49 V), substances widely used in wastewater treatment such as oxidants. Ozone is surpassed only by the hydroxyl radical (•OH) and fluoride in its oxidation capacity [7, 12].

## *2.5.1. Advantages*

Following are the advantages when ozone is used to treat water:


#### *2.5.2. Limitation*

Onsite generation is necessary as ozone is unstable at atmospheric pressure. It is toxic in high concentrations as it is a greenhouse gas. The three modules of an ozone plant are ozone destructor, ozone contact chamber, and generator. UV light or the corona discharge process is used for ozone generation. In contact chamber, ozone is added to water. The main purpose of the destructor is to limit the amount of ozone to be stripped out into the air. Three main processes affect the release of ozone after introducing ozone into water: decomposition, reaction with water impurities, and stripping into the atmosphere [14].
