Evoqua Wallace & Tiernan Depolox 3 plus, Manual

Page: 73 / 157

WT.050.560.001.UA.IM.0714 59
Depolox
®
3 plus ReSIDUAl ANAlYZeR
eVoQUA W3T140188
3.3.6 Installing the Fine Filter
NOTE: A fine filter must only be installed when membrane sensors are em-
ployed. The fine filter (C) is included in the enclosed accessory set.
1. Release both knurled nuts (A).
2. Remove complete filter unit (D).
3. Place the fine filter (C) into the filter unit. Ensure that the O-ring (B) is
seated correctly in the groove on the fine filter.
4. Reinstall the complete filter unit (D). Ensure that it is seated in the correct
position.
5. Retighten both knurled nuts (A).
3.3.7 Bare Electrode Theory of Operation
The free chlorine that is measured in water for disinfection purposes comes in
three forms. Free chlorine consists of elemental chlorine (Cl
2
), hypochlorous
acid (HClO), and hypochlorite ions (CIO-).
Hypochlorous acid is found in the acidic to neutral pH range undissociated in
water. Only when the pH value rises does it break down into H+ and ClO- ions.
To understand the mode of functioning of chlorine as a disinfectant, it is neces-
sary to know the chemical reactions that take place when water is chlorinated.
Firstly there is the hydrolysis of the chlorine. This is the reaction of the chlorine
with water. When chlorine gas is dissolved in water the formation of hypo-
chlorous acid and hydrochloric acid results. All other disinfectants based on
chlorine also react with water and form hypochlorous acid. The hypochlorous
acid is the active substance for the disinfection process. Figure 3.6 shows the
dependence of the form of chlorine on the pH value of the water. With rising