Peracetic acid (PAA) and performic acid (PFA) for water disinfection

Ravi Kumar Chhetri Postdoc

Introduction

Peracetic acid (PAA) is one of the most used disinfectants inwastewater treatment. Also used in food industry andaquaculture.

Peracetic acid is used as commercial solution in equilibrium withhydrogen peroxide:

𝐶𝐶𝐻𝐻3𝐶𝐶𝐶𝐶𝐶𝐶𝐻𝐻 + 𝐻𝐻2𝐶𝐶2↔ 𝐶𝐶𝐻𝐻3𝐶𝐶𝐶𝐶3𝐻𝐻 + 𝐻𝐻2𝐶𝐶

Does not form toxic byproducts

Hydrogen peroxide is a weak disinfectant.

(Acetic acid) (Hydrogen peroxide) (peracetic acid) (water)

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Introduction

Performic acid (PFA) is one of the most used disinfectants infood and medical industries.

Performic acid is unstable and need to synthesis before use:

𝐶𝐶𝐻𝐻2𝐶𝐶2 + 𝐻𝐻2𝐶𝐶2↔ 𝐶𝐶𝐻𝐻2𝐶𝐶3 + 𝐻𝐻2𝐶𝐶

Newly introduced disinfectant to wastewater industy Recently used in Combined Sewer Overflow (CSO) disinfection Does not form toxic byproducts

(Formic acid) (Hydrogen peroxide) (performic acid) (water)

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Combined sewer overflow

-500 E.coli/100mL-200 Enterococcus/100mL

Disinfectant profile in CSO

0 5 10 15 20 250

2

4

6 C0

Ct (t=HRT)

C·t = area under curve

dilution onrelease to surface water

Ct = Ceffluent

Reaction time (min)

Disin

fect

ant (

mg/

L)

3 design parameters

• C·t=effect concentration= area under curve

• Ct =concentration after retention time (t)=Ceffluent

• Residual toxicity

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• Modified spectrophotometric method with ABTS* for less H2O2interference. – Mixing reagent A (ABTS) and reagent B (acetic acid buffer)

*= (2, 2’’-azino-bis [3-ethylbenzothiazoline-6-sulfonic acid] diammonium salt)

Quantification method of Peracetic acid (PAA) and performic acid (PFA)

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Quantification of Peracetic acid (PAA) and performic acid (PFA)

0 10 20 30 400.0

0.2

0.4

0.6

PFAH2O2

Tid (min)

Abso

rban

s (4

05nm

)

• PAA-ABTS reaction=10 min• Color development

kinetics 2.5 mg/L PAA & 2.5 mg/L H2O2

0 1 2 3 4 5 6 7 8 9 100.0

0.2

0.4

0.6

PFAH2O2

y= 0,2452x+0,01211R2= 0.9809

mg/L

Abs

orba

ns (4

05nm

)

• PFA-ABTS reaction=20 min• Color development

kinetics 2.5 mg/L PFA & 2.5 mg/L H2O2

Kinetics of color development Calibration curve

6

0 100 200 3000

2

4

6

8

10

pH 5.18

pH 4.16

pH 8.0

pH 7.5

pH 7.5

A

Time (min)

PAA

(mg/

L)

0 100 200 3000

2

4

6

8

pH 3.78

pH 3.97

pH 6.39

pH 8.0pH 7.5

B

Time (min)

PFA

(mg/

L)

0 100 200 3000

2

4

6

8

10

5% raw WW15% raw WW40% raw WW

C

Time (min)PA

A (m

g/L)

0 100 200 3000

1

2

3

4

5% raw WW15% raw WW40% raw WW

D

Time (min)

PFA

(mg/

L)0 50 100 150 200

0

1

2

E

Sea water

Time (min)

PAA

(mg/

L)

0 50 100 150 2000

1

2

F

Sea water

Time (min)

PFA

(mg/

L)

Concentration profiles

PAA PFA

Slow degradation Fast degradation

Matrix dependent Matrix independent

pH effect Matrix effect

• 10 min contact time for Enterococcus inactivation. Reasonable robust to

matrix at 5% to 15% WW.

• Light CSO was simulated with 5% wastewater PFA is effective on

Enterococcus removal, PAA efficiency increases much more with long contact times (treatment exposure time).

Disinfection efficiency of PAA and PFA

0 10 20 30 40 50 60 70 80 90 1000.00

0.25

0.50

0.75

1.00

1.25

0

25

50

75

100

125

150

y = - 0.003 x + 1.1R2 = 0.936

PAAHP

mg(KMnO4)/L

PAA

(g/L

)

H2 O

2 (mg/L)

• Different concentration of KMnO4was used for titration

• Stability of PAA was observed for 48 h

• Re-apperance of H2O2 was studied

Solution’s characteristics before and after titration procedure.

PAA (mg/L) H2O2 (mg/L)

Initial concentration 1160 150

Concentration after titration 1010 1.5

Removal 12.9% 99%

PAA and H2O2 measured at the end of titration with differentconcentrations of KMnO4

Optimization of PAA without H2O2

Schematic diagram of RAS

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Thank you for your attention

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