**5.5. Ion exchange**

2 2 2 24

combining an oxygen atom with an oxygen molecule (O2) as follows:

*5.4.2. Ozone*

**Figure 51.** Chlorination curve [3].

40 Wastewater Treatment Engineering

*5.4.3. Ultraviolet light*

dosage can be calculated as follows:

SO +2H O+Cl H SO +2HCl SO +H O+HOCl 3H +Cl +SO

® ®

2 2 4 22 5 2 2 4 32 2 4

Na S O +2Cl +3H O 2NaHSO +4HCl NaHSO +H O+Cl NaHSO +2HCl

Ozone (O3) is a very strong oxidant typically used in wastewater treatment. Ozone is able to oxidize a multitude of organic and inorganic compounds in wastewater. These reactions cause an ozone demand in the treated wastewater, which should be fulfilled throughout wastewater ozonation prior to developing an assessable residual. Ozone should be generated at the point of application for use in wastewater treatment as ozone is an unstable molecule [3]. Figure 52 illustrates the corona discharge method for making ozone. Ozone is generally formed by

Ultraviolet (UV) radiation is a microbial disinfectant that leaves no residual. It requires clear, un-turbid, and non-colored water for its implementation. The commercial UV disinfection systems use low- to medium-powered UV lamps with a wavelength of 354 nm [3]. The UV

*D It* = ×

® ®

+ - 2-

Ion exchange (IX) is a reversible reaction in which a charged ion in a solution is exchanged with a similarly charged ion which is electrostatically attached to an immobile solid particle. The most common implementation of ion exchange method in wastewater treatment is for softening, where polyvalent cations (e.g., calcium and magnesium) are exchanged with sodium [36]. Practically, wastewater is introduced into a bed of resin. The resin is manufac‐ tured by converting a polymerization of organic compounds into a porous matrix. Typically, sodium is exchanged with cations in the solution [34]. The bed is shut down when it becomes saturated with the exchanged ions, where it should be regenerated by passing a concentrated solution of sodium back through the bed. Figure 53 shows the schematic illustration of organic cation-exchange bead. Figure 54 shows a typical ion exchange resin column. Table 4 shows the ion preference and affinity for some selected compounds.

**Figure 53.** Schematic illustration of organic cation-exchange bead [34].


**Table 4.** Ion preference and affinity for some selected compounds [3].

## **5.6. Physicochemical treatment processes**

cation-exchange bead. Figure 54 shows a typical ion exchange resin column. Table 4 shows the

ion preference and affinity for some selected compounds.

42 Wastewater Treatment Engineering

**Figure 53.** Schematic illustration of organic cation-exchange bead [34].

**Figure 54.** Typical ion exchange resin column [37].

The principal advanced physicochemical wastewater treatment processes are elucidated in Table 5.


**Table 5.** Principal advanced physicochemical wastewater treatment processes [1].
