*2.2.5. Chemicals*

NaOCl solution (or liquid bleach) is a solution with 5–15% concentration of chlorine. It is used as bleaching and cleaning agent. It is also used extensively as water disinfectant, but it may not be the most economical solution as it is more expensive than gas. Being liquid, it can be handled easily than gas or calcium hypochlorite, but it is limited by its lack of stability and corrosive nature. It can be produced easily. Continuous supply of salt and electricity is needed for onsite generation of liquid bleach. Liquid bleach has a better POU application because of its availability and relative manageability [1] (**Figure 2**).

usually provide between 1 and 295 kg of chlorine per day. At the bottom, a side stream is piped into the chlorinator. The flow arises from the holes in the sieve plate that results in eroding the last layer of tablets. The amount of water entering the chlorinator is proportional to the rate at which the tablets erode. The rate of chlorine dosage can be calculated by controlling the water flow through the chlorinator. To meet the operational requirement, the chlorinator effluent is returned to the main stream, providing the desired level of available chlorine.

Disinfection Methods

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

Variation in the dose and the contact time can be done to calculate the required disinfection. Different factors affect the chlorine dosage, i.e., wastewater characteristics, the demand of chlorine and discharge requirements. Mostly, the dose ranges from 5 to 20 mg/L. Different factors account for optimum disinfection that might include temperature, alkalinity, and nitrogen content. The pH of wastewater might affect the distribution of chlorine between hypochlorous acid and hypochlorite. A lower pH favors the hypochlorous acid: a better disinfectant. Higher concentrations of hypochlorous acid will lead to the formation of hazardous chlorine gas [2].

**1.** Either by mixing calcium hypochlorite powder in a mixing device and then injecting it into

**2.** By immersing chlorine tablets in the wastewater using a tablet chlorinator [2] (**Figure 3**).

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 compari-

can be added to the wastewater by two ways, i.e.,

son to chlorine, fewer halogenated by-products are formed [10].

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

*2.3.4. Equipment*

**2.4. Chloramines**

the wastewater stream;

Ca(OCl)<sup>2</sup>

**Figure 2.** Chlorination by chlorine liquid method.
