1. Chemical oxidation Reactants Products Reduced Oxidized Oxidants
Reductants
electrons
electron
acceptors
donors
E°reduction
E°oxidation
E°reduction> E°oxidation
Definition: Oxidation reactions are viewed as reactions involving the exchange of electrons.
TVM 4145
Vannrenseprosesser
TorOve Leiknes

2. TVM 4145
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TorOve Leiknes

3. Oxidation in water treatment:
1. Oxidation of reduced inorganic species
Fe(II), Mn(II), S(-II), As(III)
2. Oxidation of organic compounds
color removal (NOM)
hazardous synthetic compounds (i.e. TCE, atrazine)
destroy taste- and odor-causing compounds
3. Biocidal effects of oxidation
disinfection
control aquatic growth, biofilms, algae etc.
TVM 4145
Vannrenseprosesser
TorOve Leiknes

4. Oxidants used in water treatment
fluorine (f)
chlorine (Cl)
bromine (Br)
iodine (I)
Halogens:
Chlorine most used
chloramines
ozone (O3)
hydrogen peroxide (H2O2)
Fenton’s reagent (H2O2/Fe2+)
potassium permanganate (KMnO4)
oxygen (O2)
Oxidizing agents:
Advanced Oxidation Processes (AOP):
founded on use of
hydroxyl radicals (OH●)
Combining oxidizing agents, UV, catalysts etc.
TVM 4145
Vannrenseprosesser
TorOve Leiknes

5. Removal of reduced inorganic species:
soluble
insoluble
Fe/Mn:
reduced form
oxidized form
Oxidants: oxygen, ozone, permanganate, chlorine
Fe:
Kinetics:
rapid at pH > 7
1.order on Fe and O2
2.order on OH-
non-complexed forms
TVM 4145
Vannrenseprosesser
TorOve Leiknes

6. Mn: Oxidation with oxygen Kinetics: at pH > 9 slow with O2
alternative oxidants
Oxidation with permanganate
Potassium permanganate:
2. Green sand:
TVM 4145
Vannrenseprosesser
TorOve Leiknes

7. Removal of organic compounds
Oxidation attacks the carbon-carbon double bonds and splits the long molecular chain into smaller compounds
NOM:
formation of by products
complete oxidation → CO2
biodegradable compounds
formation of halogenated species
Synthetic organic compounds:
dependent on compound
competition of other constituents
dependent on pH and temperature
formation of halogenated species
TVM 4145
Vannrenseprosesser
TorOve Leiknes

8. TVM 4145
Vannrenseprosesser
TorOve Leiknes

9. TVM 4145
Vannrenseprosesser
TorOve Leiknes

10. TVM 4145
Vannrenseprosesser
TorOve Leiknes