Evoqua WALLACE & TIERNAN DEOX/2000, Инструкция по эксплуатации

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77 W3T331759 / WT.050.585.003.UE.IM.1014
MICRO/2000® AND DEOX/2000® MODULE
APPENDIX B
DEOX/2000® Reagents
List of Contents
DEOX/2000® Theory of Operation 1
Preparation of Reagents - DEOX/2000® 2
Preparation of Potassium Iodide Solution
for DEOX/2000® 2.1
1 DEOX/2000® Theory Of Operation
When a process requires super chlorination the effluent from it will have
to be dechlorinated to some extent to allow discharge, either to a sewer
or a natural water source. A variety of methods are available for de-
chlorination depending on the concentration of chlorine to be removed,
the most common being the reaction of chlorine species in the water with
sulphur dioxide (SO
2
) or sodium bisulphite (NaHSO
3
)
A range of chlorine species is typically present in industrial processes,
these ranging from hypochlorous acid (HOCl) to combined chlorine such
as chloramines. The reaction with SO
2
for these species is indicated below.
The initial step is for the formation of sulphurous acid:
SO2 + H
2
O ------> H
2
S0
3
This reacts with chlorine species as follows:
HOCl + H
2
SO
3
------> HCl + H
2
SO
4
NH
2
Cl + H
2
SO
3
+ H
2
O ------> NH
4
Cl + H
2
SO
4
NHCl
2
+ 2H
2
SO
3
+ 2H
2
O ------> NH
4
Cl + 2H
2
SO
4
This reaction with sodium bisulphite is
Cl
2
+ NaHSO
3
+ H
2
O ------> NaSO
4
+ 2HCI
The reactions show that both free and combined chlorine can be removed.
Dechlorination byproducts are ammonium chloride (NH
4
Cl), a salt,
hydrochloric acid (HCl) and sulphuric acid (H
2
SO
4
). These are naturally
neutralised by calcium carbonate (CaCO
3
) in the water, the result being
a reduction in the hardness of the water. When S0
2
is used each mg/l of
chlorine removed results in 2.8mg/l of hardness reduction and when