Page 512 - Water and wastewater engineering

DISINFECTION AND FLUORIDATION 13-7

Example 13-2. Estimate the percent available chlorine in Ca (OCl) 2 .

Solution:
a. The appropriate half reactions from Table 13-1 are

Cl g() e 2 2 Cl
2

Ca OCl 2 ) 2 H e 4 CaO H O 2 Cl
(
2
b. From the half reactions calculate the equivalent weights of Cl 2 and Ca(OCl)
2
GMW of Cl 2
.
.
Equiv Wt of Cl 2
.
No of electrons consumed
s
(
2 35 45).
35 45
.
2
(
GMW of Ca OCl) 2
Equiv Wt of Ca OCl) 2
(
.
.
No offelectrons consume d
.
.
142 98
35 45.7
4

c. The percent available chlorine is
.
35 45
% available chlorine ( 100 % 99 1.) 77%
.
35 745
Comments:
1. Although the weight percent of chlorine in Ca(OCl) 2 is barely half of the weight of the
compound, the oxidizing power is virtually equivalent to chlorine gas.
2. It is possible for a compound to have a % available chlorine greater than 100%. For these
compounds the implication is that they have greater oxidizing power than chlorine gas.

Ultraviolet (UV) Radiation. Table 13-2 outlines the spectral ranges of interest in photo-
chemistry.
The energy associated with electromagnetic radiation may conceptually be thought of as
photons. The energy is related to the wavelength of the radiation (Einstein, 1905):

hc
E (13-16)