4. Pathogen & harmful chemicals in wastewater
Pathogens and harmful chemicals in wastewater can
cause problems in ecosystem.
So, disinfection and destruction of harmful chemicals is
needed.
Disinfection technologies
1) UV 2) Chlorine 3) Ozone
4
BACKGROUND
Viruses Bacteria Protozoa Helminths Phenol Cyanide
5. Comparison
Criteria UV radiation Ozone Chlorine
Harmful byproducts NO NO YES
Environmental impact LOW LOW HIGH
Bacteria removal SOME YES YES
Virus removal NO YES SOME
Lead removal NO YES NO
Manganese removal NO YES SOME
Iron removal NO YES YES
Odor removal NO YES YES
Color removal NO YES SOME
Operational cost MED LOW MED
Capital cost MED HIGH MED
Maintenance HIGH MED MED
5
BACKGROUND
(Marianne, 1997)
6. What is ozone
O3
Unstable structure -> High reactivity
Pale blue gas
Distinctively pungent smell
INTRODUCTION
6
7. Much higher solubility into water than O2
Strong oxidizing agent
Easy to produce with air or oxygen gas and electricity
Ozone’s strength
INTRODUCTION
7
● Oxygen
Reactions :
1) O2 + e → 2O + e
2)O2 + O + M → O3
water
O2
O3
1)
2)
O3 109mg/L ≫ O2 18mg/L at 25℃
(Ozone solutions, 2014)
8. pH dependence of dissolved ozone
Dissolved O3 has pH dependence.
In basic environment, ozone decomposes rapidly.
And OH-radicals are produced.
OH-radical is the strongest oxidant.
The higher pH, the more OH-radicals.
INTRODUCTION
8
(Lenntech, 2010)
13. Ozone treatment system is placed at the end of
wastewater treatment system.
ACTUAL CASES
Ozone treatment system
13
Wastewater treatment system
14. Disinfection performance
14
Coliform : E.coli-like
(Hoveid H. et al, 2008)
ACTUAL CASES
Bacteria totally removed in 10 min. of contact time and
with 1ppm of ozone concentration
16. COD removal performance
16
(Preethi V. et al, 2009)
ACTUAL CASES
COD of tannery effluent decreases by ozonation.
COD removal efficiency is related to concentration of
ozone and pH.
17. AOP (advanced oxidation process)
AOP is a set of chemical treatment procedure to remove
organic materials in wastewater by oxidation through
reactions with the strongest oxidant ·OH.
Better than ozonation alone
Combinations
1) O3/H2O2 : peroxonation
2) O3/UV : ozone photolysis
3) H2O2/UV
4) H2O2/Fe2+/UV
17
(Mehmet A. et al, 2014)
.
.
.
AOP
18. Peroxonation (O3/H2O2)
Reaction
H2O2 accelerates the decomposition rate of O3.
It produces a larger number of very reactive ·OH
radicals.
Peroxonation process is more efficient than ozonation
alone.
Essential step of disinfection
18
AOP
(Mehmet A. et al, 2014)
19. Ozone photolysis (O3/UV)
Reaction
Effective on eliminating various volatile chlorinated
organic compounds
ex) CHCl3, CCl4, trichloroethylene(TCE) etc.
19
(Mehmet A. et al, 2014)
AOP
20. AOP in Petrochemical wastewater treatment
190 tons/months of phenolic wastes disposes by petrochemicals,
pharmaceuticals, and polymer industries.
2-Nitrophenol(2NP) is a main pollutant from petrochemical
wastewater.
Shokri applied ozone to degrade 2NP.
Ozonation at high pH (pH = 9) generates OH-radical rapidly. (=AOP)
20
(Shokri A., 2015)
AOP
Removal rate (%)
2NP 99.8
TOC 31
COD 72.5
21. Coking wastewater treatment
O3 & H2O2/O3 is applied to remove cyanide from coking wastewater.
Oxidation process is combined with coagulation-flocculation-
decantation and lime-soda ash softening pretreatment.
Using lower concentrations of ozone, cyanide is not removed.
Ozone consumption without softening pretreatment is twice as much
as that with softening pretreatment because wastewater contains
bicarbonate ions.
21
(Pueyo N. et al, 2016)
COMBINED TREATMENT
22. Textile wastewater treatment
Textile wastewater contains acute toxic chemicals.
Pazdzior et al studied the effect of ozonation & biodegradation on
toxicity.
Ozonation is combined with aerobic biodegradation.
22
(Pazdzior K. et al, 2016)
COMBINED TREATMENT
Toxicity removal
O3 →Bio 76.2 – 92.2%
Bio→ O3 93.7 – 94.2%
Bio→ O3 →Bio ~ 96%
raw
O
3
Bio
O
3
→Bio
Bio
→
O
3
Bio
→
O
3
→
Bio
Toxicity after treatment
23. Oilfield wastewater treatment
3 steps to enhance biodegradability of oilfield produced water(OPW)
1. Microwave demulsification : to remove oil
2. Ozone oxidation : to enhance the biodegradability of wastewater
3. Biological aerated filter : aerobic digestion
BOD5/COD shows the biodegradability of wastewater.
The optimum ozone treatment condition
- Dosage : 7mg/L
- Contact time : 15min
23
(Kang J. et al, 2015)
Parameter Initial value
pH 6.6
COD (mg/L) 648
BOD5 (mg/L) 45
BOD5/COD 0.07
Oil (mg/L) 68
TPH (mg/L) 76
SO4
2- (mg/L) 34
NH3-N (mg/L) 52
PS (mg/L) 589
TSS (mg/L) 3,346
Microtoxicity (EC50, %) 8.6
▶Charateristics of OPW
(Rajakovic V. et al 2006)
COMBINED TREATMENT
24. Oilfield waster treatment
Result
After biological treatment, effluent satisfies Chinese discharge
standard.
Ozone decomposes complex chemicals biodegradable.
24
(Kang J. et al, 2015)
Parameter Initial value After microwave treatment After ozonation
COD (mg/L) 648 382 260
BOD5 (mg/L) 45 21 86
BOD/COD 0.07 0.08 0.33
Oil (mg/L) 68 25 16
TPH (mg/L) 76 28 18
NH3-N (mg/L) 52 43 37
PS (mg/L) 58 58 12
Microtoxicity (EC50, %) 8.6 8.8 31
COMBINED TREATMENT
25. Conclusion
Ozone can degrade various types of chemicals or microbe with its
strong oxidizing power.
Many studies proved that ozonation is effective not only on
municipal wastewater but also on industrial wastewater.
pH of wastewater and concentration of ozone is important on
effectiveness of ozonation.
Basic environment(>pH 7) is favorable for ozonation.
Lower concentration of ozone may not be effective.
Ozonation can need pretreatments according to condition of
wastewater.
Ozonation shows better performance when it is combined with
other water treatment technologies.
25
CONCLUSION
