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Evaluation of the Physical–Chemical Characteristics
of Wastewater After Disinfection with Peracetic Acid
Grasiele Soares Cavallini & Sandro Xavier de Campos &
Jeanette Beber de Souza & Carlos Magno de Sousa Vidal
Received: 19 December 2012 /Accepted: 10 September 2013
# Springer Science+Business Media Dordrecht 2013
Abstract The use of peracetic acid (PAA) in the dis-
infection of sanitary effluents has been proposed by
various authors. However, there are still doubts about
its influence on the physical–chemical characteristics
of the effluent after application. In the present study, it
was observed that the composition of PAA leads to an
increase in organic material, resulting in an increase of
approximately 20 mg/L in the chemical oxygen de-
mand of the effluent for every 10 mg/L of PAA applied.
According to the kinetic tests, the degradation of PAA
in the effluent was represented by a first-order reaction
and its half-life in the effluent was estimated at
79 min. The formation of by-products resulting
from degradation of PAA in the effluent was eval-
uated by considering by-products already detected
by other authors in disinfection trials, these being
nonanal, decanal, chlorophenols, and 1-methoxy-4-
methylbenzene, which were not observed in the
effluent being studied after application of PAA at
a dosage of 10 mg/L.
Keywords Peracetic acids . Physical–chemical
characteristics . Degradation kinetics . By-products
1 Introduction
The pioneers in the study of peracetic acid (PAA;
CH3COOOH) as a disinfectant in the treatment of
effluents were Baldry and French (1989). They de-
scribed the efficiency of PAA, relating the time of
contact and the concentration of the disinfectant in
the removal of coliforms (Kitis 2004).
When compared with sodium hypochlorite, PAA
has similar bactericidal power in relation to the micro-
organisms Salmonella sp., Pseudomonas sp., total co-
liforms, fecal coliforms, and Escherichia coli. How-
ever, the initial concentration of PAA in wastewater
must be three to eight times greater than the concen-
tration of sodium hypochlorite in order to reduce the
microorganisms fecal streptococcus and anti-E. coli
bacteriophages to 10 % of the initial population
(Veschetti et al. 2003).
Koivunen and Heinonen-Tanski (2005) observed
that the efficiency of disinfection with PAA was rela-
tively constant in secondary and tertiary effluents since
Water Air Soil Pollut (2013) 224:1752
DOI 10.1007/s11270-013-1752-5
G. S. Cavallini (*)
Laboratory of Environmental Sanitation and Water Quality,
State University of the Centro-Oeste (UNICENTRO),
PR 153 km 7, Riozinho, Irati, Parana 84500-000, Brazil
e-mail: grasielesoares@gmail.com
S. X. de Campos
State University of Ponta Grossa—UEPG,
Post-Graduation Program in Applied Chemistry,
Avenue General Carlos Cavalcanti, 4748, Uvaranas,
Ponta Grossa 84030-900 Parana, Brazil
J. B. de Souza :C. M. de Sousa Vidal
Department of Environmental Engineering, UNICENTRO,
PR 153 km 7, Riozinho, Irati, Parana 84500-000, Brazil
they have similar chemical oxygen demand (COD),
turbidity, and total solids (TS); however, in primary
effluents in which the levels of total solids in suspen-
sion (TSS), organic material, and microorganisms were
higher, the efficiency of disinfection decreased consid-
erably. The decrease in the efficiency of inactivation
resulting from the elevated levels of organic material in
the effluent and the resistance of some microorganisms
demands larger doses of disinfectant. In the case of
PAA, a quaternary mixture in equilibrium (reaction 1),
the addition of the disinfectant can cause an increase in
the organic material in the effluent, interfering with the
final characteristics of the effluent after treatment and
release into bodies of water (Lazarova et al. 1998;
Sartori 2004; Souza 2006; Costa 2007).
CH3COOH þ H2O2⇌CH3COOOH þ H2O ð1Þ
The spontaneous decomposition of PAA in oxygen
and acetic acid (Sanchez-Ruiz et al. 1995), a biode-
gradable organic compound, creates doubts about the
possibility of bacteria to use the oxygen liberated for
degradation of the organic material generated during
the disinfection.
Also, the addition of an acidic substance to the
effluent leads to a decrease in pH, and thus, the impor-
tance of studying alterations in the physical–chemical
characteristics of the effluent after disinfection with
PAA is to observe whether these alterations are harmful
to aquatic life and the reactions of autodepuration.
The kinetics of PAA degradation in the effluent
contribute to the estimation of the time it remains in
the effluent and also to the evaluation of which phys-
ical–chemical characteristics of the effluent can influ-
ence this degradation.
The consumption and the efficiency of PAA in the
disinfection of wastewater can vary according to con-
tact time, temperature, pH, and the amount of organic
material and solids in the effluent (Sanchez-Ruiz et al.
1995; Lazarova et al. 1998; Falsanisi et al. 2008). Even
after disinfection, the rapid degradation of PAA in the
effluent demonstrates its instability, mostly in low
concentrations.
Rossi et al. (2007) affirmed that the kinetics of
degradation of PAA are relevant since it is a mixture
in equilibrium, which leads to a natural decrease of the
concentration of PAA available for disinfection.
The decomposition of PAA in acetic acid and oxy-
gen is amply publicized; however, some authors try to
assure themselves of this affirmation before proposing
the substitution of chlorine by PAA, emphasizing that
the variable chemical composition of residual water
makes necessary more rigorous monitoring with re-
spect to its genotoxicity and toxicity for a final evalu-
ation of its applicability (Crebelli et al. 2005) since the
formation of by-products is possible.
In this context, the present study also includes re-
search of the length of time PAA remains in the effluent
before being completely degraded, observing its reac-
tion order and its half-life, to estimate the stability of
this disinfectant in the effluent.
2 Materials and Methods
The studies were performed using the final effluent of the
wastewater treatment plant (WWTP) Rio das Antas, locat-
ed in Irati, Paraná, Brazil, and operated by the Companhia
de Saneamento do Paraná, Brazil (SANEPAR). This plant
has been in operation since 1990 and serves a population
of approximately 40,000 residents. Its flow rate is 50 L/s.
The Rio das Antas WWTP includes primary treatment,
screening and grit chamber, and secondary treatment
consisting of a UASB reactor, followed by a facultative
pond and sludge drying bed.
The PAAbeing studiedwas of 15% (m/v) concentration,
manufactured by Peróxidos do Brasil (PROXITANE®
1512). The applications were performed using a recently
prepared standard solution of 1,000 mg/L.
The methodology adopted for the physical–chemical
characterization of the effluent followed the description
found in the Standard Methods for the Examination of
Water and Wastewater (APHA/AWWA/WEF 1998).
Initially, the effluent was characterized according to
the following parameters: pH, total coliforms (TC), E.
coli, temperature, turbidity, alkalinity, TSS, TS, COD,
and dissolved oxygen (DO), according to the method-
ologies described in the Standard Methods for the
Examination of Water and Wastewater (20th edition;
APHA/AWWA/WEF 1998).
The PAAwas applied in 13 different dosages varying
from 5 to 100 mg/L (5, 10, 15, 20, 25, 30, 40, 50, 60, 70,
80, 90, and 100 mg/L), using a standard solution of
1,000 mg/L of PAA. Aliquots of 1,000 mL of effluent
were placed in beakers, and the PAA was applied
according to each dosage, totaling 13 samples. After the
application of PAA, the analyses of COD, BOD, DO, and
pH were performed.
1752, Page 2 of 11 Water Air Soil Pollut (2013) 224:1752
COD was determined by a spectrophotometricmeth-
od, through the chemical reaction of the organic material
in the sample, particulate or dissolved, with potassium
dichromate in sulfuric acid. In this method, the follow-
ing was placed in a cuvette: 2.5 mL of sample, 3.5 mL of
digestion solution (10.12 g of silver sulfate in 1 L of
concentrated sulfuric acid), and 1.5 mL of chromophore
solution (12 mol/L sulfuric acid, 33.3 g of mercury
sulfate, and 10.2 g of potassium dichromate). After this,
the sample was digested in a BR750 BIOTECH digestor
for 2 h at 148 °C. The reading was performed on a
HACH DR 2800 spectrophotometer with a wavelength
of 620 nm, when the sample reached room temperature.
Using the analytic curve plotted previously, the values
of COD (mg O2/L) were found.
For determination of DO and BOD, the samples
were placed in specific flasks for analysis, slowly, so
that DO values were not altered, and the measurements
were taken with an ORION oximeter. The equipment
was calibrated through the saturation of water in the air,
as recommended by the manufacturer. The DO read-
ings were performed shortly after the application of
PAA. For BOD the samples were diluted as necessary
for each sample, and the final DO was determined after
the samples were incubated at 20 °C for 5 days.
The pH was determined by a potentiometric method
using a combined glass electrode.
2.1 Data Analysis
The data were submitted to simple regressions; the
choice of the best models was based on the highest
determination coefficient, adjusted by the degrees of
freedom (R2adjusted), and the lowest standard error. The
residual normality was verified by the Kolmogorov–
Smirnov test and the independence of residuals by the
Durbin–Watson test, both at 5 % of significance (ZAR
1999). All analyses were performed with the software
Statgraphics Plus 5.1.
2.2 Kinetic Trials of Degradation of PAA
in the Effluent
The determination of residual PAA was performed by
visible spectrophotometry. The spectrophotometric method
used the chromophore N,N-diethyl-p-phenylenediamine
(DPD; (C2H5)2C6H4NH2, 97 %, ALDRICH), which, in
the presence of the oxidant, has a reddish coloration, using
potassium iodide as a catalyst. This chromophore reacts
with other oxidants such as hydrogen peroxide and chlo-
rine, so catalase was used to decompose the hydrogen
peroxide in the samples.
The methodology adopted was adapted from the pro-
cedure described by Falsanisi et al. (2006), inwhich 10mL
of sample was added to 2 mL of catalase (50 mg/L), to
which 0.5 mL of a solution containing 0.037 mmol/L of
H2SO4, 0.54 mmol/L of EDTA, and 0.061 mmol/L of
DPD and 0.5 mL of pH 6.5 phosphate buffer solution
(0.18 mmol/L of disodium hydrogen phosphate dihydrate,
0.34 mmol/L of KH2PO4, 0.074×10
−6 mol/L of HgCl2,
and 0.0060 mmol/L of KI) were then added. The reading
was performed at a wavelength of 530 nm.
After the analytic curve was plotted, PAA was deter-
mined continuously, in a sample of the effluent containing
10mg/L of PAA, until there was no oxidant remaining. To
avoid the interference of chlorine and other oxidants pres-
ent in the effluent itself, a sample containing the effluent
without PAA was used as a reference and the value
subtracted from each reading.
2.3 Determination of By-products Resulting
from the Disinfection with PAA
Through the results obtained by Monarca et al. (2004)
and Nurizzo et al. (2005), it was possible to select the
by-products that could be present in the effluent being
studied after application of PAA, as shown in Table 1.
Based on these compounds, the methods of deter-
mination of these by-products were established.
The analyses were performed using a HP 5890
chromatograph with a flame ionization detector (FID).
For determination of the aldehydes (nonanal and
decanal), a DB5 30 m×0.25 mm silicon dioxide capil-
lary column was used, with high-purity purge gases
(4.5/4.7; flow rates: hydrogen, 15–25mL/min; synthetic
air, 250–300 mL/min; and nitrogen, 6–8 mL/min). The
operation ramp was as follows: 35 °C for 2 min,
12 °C/min for 5 min, and 10 °C/min up to 265 °C for
12 min. The injector temperature was 200 °C and the
detector temperature 250 °C (maximum temperature of
250 °C).
The determination of 1-methoxy-4-methylbenzene
and the chlorophenols was performed in a DB 624
(J&W Scientific) 30 m×0.5 mm chromatographic
column/3.0 μm film, with high-purity purge gases
(4.5/4.7; flow rates: hydrogen, 30–40mL/min; synthetic
air, 250–300 mL/min; and nitrogen, 6–8 mL/min). The
initial operation ramp was 45 °C for 3 min and 8 °C/min
Water Air Soil Pollut (2013) 224:1752 Page 3 of 11, 1752
up to 220 °C for 15 min. The temperature of the injector
was 180 °C and that of the detector 200 °C (maximum
temperature of 250 °C).
3 Results and Discussion
The effluent being studied showed stable physical–
chemical and bacteriological characteristics. The fol-
lowing are the maximum and minimum values of the
six samples taken: BOD=30–33 mg/L, COD=129–
148 mg/L, DO=3.6–5.8 mg/L, TSS=28–96 mg/L,
TS=330–474 mg/L, alkalinity=84–119 mg/L, E. coli=
105–106 colony-forming units(CFU)/100 mL, and
TC=105–106 CFU/100 mL.
3.1 pH Tests
The tests of pH variation showed less variation with the
application of PAA in the effluent. Figure 1 shows the
results obtained in three trials, with each trial
performed in triplicate and represented by its mean.
The pH variation in this effluent was within the limit
defined by Brazilian standards (CONAMA Resolution
357/05 2005), which is a pH between 6.0 and 9.0, and
this is because PAA is a weak acid and when combined
with the alkalinity of the effluent, the pH was not
significantly affected.
The functional group of PAA is classified as a
percarboxylic acid, and according to Brasileiro et al.
(2001), the peracids in solution are more volatile and
less acidic than their corresponding carboxylic acids.
Sartori (2004) and Souza (2006), in testing lower
dosages, also did not observe significant changes in the
pH with the application of PAA, in a secondaryWWTP
effluent and in water.
3.2 COD Tests
To evaluate the variation in COD with the application
of PAA in the effluent, five trials were performed. The
results obtained are presented in Fig. 2, which shows
the linearity of the values through the arithmetic mean
of the five trials.
According to the results presented in Fig. 2, it was
noted that the application of PAA resulted in a mean
COD increase of 19.4±2.5 mg/L for each 10 mg/L of
PAA applied. This experimental result is lower than that
Table 1 By-products of disinfection with PAA observed by Monarca et al. (2004) and Nurizzo et al. (2005)
By-products
Aldehydes Nonanal and decanal
Phenols Chlorophenol
Benzene derivatives 1-Methoxy-4-methylbenzene
Fig. 1 Variation in pH for different dosages of PAA. R2=0.939,
standard error=0.099, F1-40=634.58, P<0.01
Fig. 2 Variation in COD for different dosages of PAA. R2=
0.896, standard error=0.691, F1-68=597.90, P<0.01
1752, Page 4 of 11 Water Air Soil Pollut (2013) 224:1752
expected by Kitis (2004), who described that the in-
crease of COD for each 5 mg/L of PAAwould theoret-
ically be 14 mg/L. This being the case, the experimental
mean obtained is 30 % lower than expected, showing
that part of the organic material in the effluent may have
been oxidized by PAA.
Sartori (2004) and Costa (2007) also observed an in-
crease of COD in secondary wastewater effluents with the
application of PAA, but they did not describe the propor-
tion of increase. Souza (2006) observed an increase of
organic material coming from PAA through the determi-
nation of total organic carbon (TOC). Lazarova et al.
(1998) used the same parameter and obtained values three
times greater than the initial concentration of TOC after the
application of 10 mg/L of PAA in wastewater. However,
conflicting results were obtained by Baldry(1995), in
which the COD decreased from 52.2 to 44.7 mg/L with
the application of PAA in samples of treated urban
wastewater.
In general, it can be observed that the use of PAA
requires caution with regard to the increase of organic
material since the application of PAA in effluents that
already have high COD levels may be contraindicated,
and even in effluents with low COD, dosages up to
10 mg/L are the most ideal.
3.3 DO Tests
The results obtained through the monitoring of DO after
the application of PAA are shown in Fig. 3. The results
obtained showed that the application of PAA contributed
to the increase of DO in the effluent, maintaining a direct
relation with temperature. At a temperature of 23 °C with
a dosage of 30 mg/L of PAA, the concentration of DO
reached saturation, while a dosage of 40 mg/L or higher
resulted in the supersaturation of the effluent. At lower
temperatures, a decrease in the concentration of DO can
be observed, even at high dosages of PAA.
The liberation of oxygen into the effluent is due to
the decomposition of PAA and hydrogen peroxide, as
shown in reactions 2 and 3, respectively:
2CH3COOOH→2CH3COOH þ O2 ð2Þ
H2O2→H2Oþ 1
�
2
O2 ð3Þ
Another possible means of oxygen liberation is by
the reduction of nitrate to nitrogen in gaseous form
(reaction 4) (Sperling 2005), in which H+ ions can be
provided by the ionization of acetic or peracetic acid:
2NO3 þ 2Hþ→N2 þ 2:5O2 þ H2O ð4Þ
The release of oxygen by reactions 2 and 3 is limited
with decreasing temperatures, increasing the amount of
time necessary for decomposition of PAA.
The oxygen release after application of 10 mg/L of
PAA at 15 °C can be observed in the trial shown in
Fig. 4. According to the results shown in Fig. 4, it can
be seen that the release of oxygen at 15 °C occurs
primarily in the first 2 h after the application of PAA.
After this period, the concentration of oxygen increases
slowly and not as significantly, which could indicate
the endpoint of PAA decomposition.
Since DO is a parameter of great relevance to the quality
of bodies of water, the release of effluents with high DO
concentrations could be another advantage of PAA applica-
tion, in addition to deactivation of microorganisms.
3.4 BOD Tests
For evaluation of the influence of PAA on BOD, an
initial dosage of 10 mg/L of PAA was used, and the
results obtained are shown in Table 2. With the 10 mg/L
dosage of PAA, there was no significant change in the
BOD of the effluent, which shows that this concentra-
tion of PAA did not have a negative impact on bacteria
performing decomposition in the effluent.
Fig. 3 Increase in DO for different dosages of PAA at different
temperatures (15, 18, and 23 °C). 15 °C—equation: DO=
5.88781+0.0236315*PAA, R2=0.961, standard error=0.15, F1-40=
1,002.85, P<0.01. 18 °C—equation: DO=4.6271+0.0866229*PAA,
R2=0.979, standarderror=0.42,F1-12=609.18,P<0.01.23°C—equation:
DO=5.83319+0.098362*PAA, R2=0.970, standard error=0.40, F5-36=
423.62, P<0.01
Water Air Soil Pollut (2013) 224:1752 Page 5 of 11, 1752
Stampi et al. (2001) used dosages of 1.5 to 2 mg/L
of PAA for disinfection of a secondary effluent and
observed a decrease in the BOD of the effluent (from
41 to 36 mg/L), while Baldry (1995) observed a de-
crease of BOD (from 23 to 16 mg/L) in an effluent of
urban wastewater when 5 mg/L of PAAwas applied.
The slight decrease of the BOD could indicate the
contribution of the PAA, and thus, higher dosages were
tested to evaluate this property.
Figure 5 shows the results obtained in the four tests,
with effluents collected on different dates, using dosages of
PAA that varied from 5 to 100mg/L of PAA. According to
the results obtained, the effluent did not show a significant
variation up to 30 mg/L of PAA. Beginning at 50 mg/L,
the final DO was greater than the initial value (values
greater than 10 mg/L), and thus, the values of BOD were
represented as zero.
Lazarova et al. (1998) determined the biodegradable
dissolved organic carbon (BDOC) in wastewater
disinfected with 5 mg/L of PAA, obtaining a concen-
tration four times greater than the initial concentration.
This parameter is directly related to BOD; however, the
BOD analysis was not performed by these authors.
One thing that could justify the increase in BDOC
with the addition of PAA, as found by Lazarova et al.
(1998), without affecting the BOD of the effluent, is
the increase of DO provided by the decomposition of
PAA, in which the concentration of oxygen released is
sufficient for the degradation of the biodegradable
organic material generated for dosages up to 30 mg/L
of PAA in the effluent being studied.
The COD after 5 days was performed to verify the
amount of organic material after the oxidation of the
biodegradable material, as seen in Fig. 6. In both experi-
ments, therewas a decrease in the CODof the effluent after
the effluent was incubated for 5 days with the disinfectant.
At dosages lower than 40 mg/L, the decrease in COD
that could be attributed to oxidation of the biodegrad-
able organic material was more visible. This indicates
that starting at 40 mg/L, the decrease of BOD becomes
easier to justify by the interruption of the activity of the
bacteria decomposing the organic material, due to the
high dosages of PAA, and thus, it was not possible to
observe the consumption of the oxygen released or the
proportional decrease in COD.
The results obtained in these experiments empha-
size the importance of toxicological tests, primarily
when using dosages higher than 30 mg/L.
3.5 Some Factors that Influence the Consumption
of PAA in the Effluent
In disinfection trials, the consumption of the oxidant
corresponds not only to the concentration consumed to
Fig. 4 Oxygen release in the
decomposition of PAA
(10 mg/L) in the effluent
Table 2 Influence of the application of PAA on BOD of the effluent
Sample BOD (mg/L)
Raw effluent 22.6
Effluent with PAA (10 mg/L) 20.8
Characteristics of the effluent: turbidity=20 NTU, TS=324 mg/L, COD=105 mg/L, DO=4.18 mg/L, pH=7.7
1752, Page 6 of 11 Water Air Soil Pollut (2013) 224:1752
inactivate the microorganisms but also to the portion of
disinfectant degraded due to the physical–chemical
composition of the effluent, which can generally be
attributed to the oxidation of the organic material and
its decomposition by interferents such as metals.
Proof of this is that the consumption of PAA in the
effluent is more directly related to the physical–chem-
ical conditions of the effluent than to its initial concen-
tration. Table 3 shows an average value for the con-
sumption of PAA, varying the dosage of the disinfec-
tant applied.
Through the trials, it was possible to select the dosage of
10 mg/L of PAA to serve as the standard dosage in the
degradation studies. This dosage was used to guarantee
that the PAAhad a high enough concentration even though
the effluent had physical–chemical and microbiological
conditions that required higher doses of disinfectant.
The consumption of the disinfectant showed greater
alterations with variations in pH and TSS. Figure 7 is a
graphic representation of these variations.
The range of the lowest consumption of PAA was
found in the trials with pH below 7.0, where sulfuric acid
was added. This is because the addition of sulfuric acid
catalyzes the equilibrium of the mixture: acetic acid,
hydrogen peroxide, and PAA, preventing its decomposi-
tion (Block 2001; Zhao et al. 2007; Zhao et al. 2008). The
absence of sulfuric acid in the ranges of alkaline pH did
not interfere with the decomposition of PAA and thus
shows greater consumption of the oxidant.
In addition, PAA in alkaline pH is found principally
in dissociated form, not active, since its pKa is 8.2
(Sanchez-Ruiz et al. 1995).
As for the presence of TSS in the effluent, it can be
observed that the consumptionof PAA increases with
higher concentrations of TSS, demonstrating the con-
sumption of the oxidant by the material in suspension
(<1.2 μm), since the concentrations of microorganisms
E. coli and TC remained within the same logarithmic
order while the TSS varied. Lazarova et al. (1998)
observed that TSS up to 10 mg/L increases the demand
of PAA for inactivation of microorganisms. From 10 to
40 mg/L, the impact caused by the solids in suspension
becomes constant. In other words, even with the in-
crease of the oxidant, there is no increase in the effi-
ciency of inactivation.
This is because coliform bacteria can be present in
the effluent in two forms: associated with particulate
material or dispersed in the solution. According to
Sanchez-Ruiz et al. (1995), PAA can be applied in
effluents with TSS up to 100 mg/L. This is because
the increase in TSS causes most of the bacteria to be
associated with particulate material in the effluent, and
with this, the demand for disinfectant increases and the
efficiency of inactivation of microorganisms decreases
because they are protected by solids in suspension
Fig. 5 Variation in BOD for different dosages of PAA. R2=0.55, standard error=7.52, F1-22=28.82, P<0.01
Fig. 6 Comparison of COD at the moment of PAA application
and after 5 days
Water Air Soil Pollut (2013) 224:1752 Page 7 of 11, 1752
(Sanchez-Ruiz et al. 1995; Lazarova et al. 1998;
Falsanisi et al. 2008).
Even though the constant variation in the physical–
chemical conditions of the effluent does not permit an
exact estimate of the time required for degradation of
PAA, it is still possible to estimate, in lower concen-
trations of TSS, the maximum time it may remain in
the effluent being studied.
3.6 Kinetics of Degradation of PAA in the Effluent
The kinetics of degradation of the disinfectant is a very
important area in the study of environmental chemistry
as this information permits the estimation of how long
it remains in the environment. If the application of the
disinfectant implies the addition of a persistent organic
compound, then its use is not feasible, preventing the
autodepuration of the effluent.
The kinetic trials were performed with two samples
of effluent, collected on different days, to compare
them. The dosage of 10 mg/L of PAA was applied in
order to observe its speed of degradation at 25 °C.
The two trials performed showed similar values of
residual PAA as a function of time since the values of
TSS were similar. The kinetic calculations were
performed in TSS of 28 mg/L, which corresponds to
the lowest concentration of TSS observed in the efflu-
ent being studied.
For determination of the order of the reaction, the
integration method was used. The first step was the
calculation as if it were a first-order reaction, so the
graph with the natural log (ln) of the concentration of
PAAwas plotted as a function of time, using the values
Table 3 Consumption of PAA during the disinfection trial
PAA (contact time 20 min)
[PAA] applied (mg/L) E. coli (CFU/100 mL) TC (CFU/100 mL) [PAA] consumed (mg/L) % consumed
5 1.7×106 5.2×106 3.09 62
10 4×102 5.3×103 4.87 49
15 3×102 2.4×103 3.71 25
20 2×102 1.4×103 5.5 27
25 3×102 3.8×103 5.98 24
30 2×102 2×103 4.64 16
2×102 2×103 Mean 4.63±1
Physical–chemical conditions of the effluent: pH=7.38, turbidity=26.9 NTU, TSS=56 mg/L, TS=474 mg/L
Fig. 7 a Consumption of PAA when varying the pH of the
effluent. Physical–chemical conditions of the effluent: turbidi-
ty=16.8 NTU, TSS=28 mg/L, TS=306 mg/L, alkalinity=38 mg/
L. b Consumption of PAAwhen varying the TSS of the effluent.
Physical–chemical conditions of the effluent (mean values of the
trials): turbidity=22±4 NTU, pH=7.6±0.15, E. coli=105 CFU/
100 mL, TC=106 CFU/100 mL
1752, Page 8 of 11 Water Air Soil Pollut (2013) 224:1752
from trial 2, as shown in Fig. 8a. In the second step,
calculations for a second-order reaction were performed
using the values of [1/(concentration of PAA)] as a
function of time, as seen in Fig. 8b.
From the graphs, it could be observed that the de-
composition of PAA in the effluent being studied is a
first-order reaction since it had a R2 closer to 1. Be-
cause of this, the plot of the natural log of the concen-
tration of PAA as a function of time was more linear, or
in other words, the concentration of PAA decreased
exponentially with time, different from second-order
reactions, which maintain low concentrations of re-
agents for a long period of time, thus frequently caus-
ing environmental problems.
With the results obtained, the integrated velocity
law of the reaction can be defined, and since it is a
first-order reaction, it is given by Eq. 5:
C½ �t ¼ C½ �0⋅e−kt ð5Þ
where the velocity constant k corresponds to the slope,
which in this case is equal to 0.0088, considering the
time in minutes and the concentration of PAA in mil-
ligrams per liter. In this way, it is possible to estimate
the concentration of PAA in this effluent at any time, as
long as the initial concentration is known.
The equation proposed by Rossi et al. (2007) better
represents the kinetic behavior of PAA, where the
initial concentration of PAA is the dosage applied
(C0) minus the initial oxidative consumption (D), as
shown in Eq. 6:
C½ �t ¼ C0−D½ �⋅e−kt ð6Þ
It is important to note that Rossi et al. (2007) obtained
their results in tests with drinking water. According
Zhao et al. (2008) Koubec in 1964 obtained a second-
order reaction when investigating the decomposition of
PAA in distilled water. Zhao et al. (2008) also obtained a
second-order reaction when investigating the spontane-
ous decomposition of PAA in an acidic medium. In
saline conditions, Shikishima et al. (2008) obtained a
first-order reaction, which could indicate that the pres-
ence of chloride ions (173 mg/L) in the effluent may
have contributed to the degradation of PAA being a first-
order reaction.
Another important piece of information provided by
the velocity constant is the half-life, or the time neces-
sary for half of the applied dosage of PAA to be
decomposed. For a first-order reaction, as is the case
in the degradation of PAA in the effluent, the equation
is expressed by
t
1
.
2
¼ ln2
.
k ð7Þ
This being the case, the estimated half-life for deg-
radation of PAA in the effluent being studied is ap-
proximately 79 min.
The rapid degradation of PAA in the effluent requires
attention to the possibility of the re-growth of bacteria, a
process that could be intensified by the presence of
acetic acid which, being biodegradable, ends up provid-
ing nutrients for bacteria, thus helping to re-establish the
microorganism (Lazarova et al. 1998).
Rossi et al. (2007) estimated the half-life of PAA in
tap water and obtained t1/2=100 min since the initial
concentration of PAA decreased 25 to 30 % in 60 min.
In comparison with the data obtained by Rossi et al.
(2007), this study obtained a decrease of about 20 % of
the half-life of PAA when applied in the effluent, and
this can be attributed to the consumption during the
disinfection and oxidation of organic material. In the
Fig. 8 Determination of the order of the reaction. a First-order. b Second-order
Water Air Soil Pollut (2013) 224:1752 Page 9 of 11, 1752
effluent being studied, approximately 16 % of the PAA
was consumed immediately upon application.
From an environmental point of view, the kinetic
behavior shown by PAA in the effluent being studied is
positive since if the oxidant remained in the effluent for
a long period of time, it could contribute to the forma-
tion of by-products, even in low concentrations.
3.7 Determination of Possible By-products
of Disinfection with PAA
Based on results obtained by other authors, some possi-
ble by-products were selected to be determined after
application of PAA in the effluentbeing studied. Table 4
shows these substances and the results obtained through
the chromatographic analyses. The application of PAA
in the effluent did not result in the formation of any of
the substances determined, contrary to the results
obtained by Monarca et al. (2004).
The reduction of chlorophenol obtained cannot be
affirmed since the variation could have been due to the
particular sample. In this case, more trials should be
conducted to confirm or disprove this reduction. The
values of chlorophenol obtained agree with Booth and
Lester (1995), who discarded the possibility of PAA
oxidizing chloride ions to hypochlorous acid and
forming chlorophenols.
The fact that these substances were not detected is a
positive indicator for the use of PAA in the disinfection
of effluents.
4 Conclusion
Evaluating the results obtained, it can be concluded
that:
– The application of PAA in dosages commonly
used for disinfection (up to 10 mg/L) did not
significantly change the physical–chemical char-
acteristics of the effluent, especially in relation to
pH.
– Considering that the increase in organic material in
sanitary effluents has the greatest impact on the
increase in consumption of the oxygen dissolved
by the bacteria performing decomposition, the in-
crease in the biodegradable organic material
resulting from the use of PAA as a disinfectant
can be lessened or impeded by its own capacity
to oxygenate the effluent, when used in dosages up
to 30 mg/L.
– Dosages higher than 40 mg/L can be harmful to the
bacteria performing decomposition, which must
be evaluated through toxicological tests.
– The length of time the PAA remained in the efflu-
ent being studied was approximately 6 h and
30 min for the dosage of 10 mg/L, a relatively
short period of time, which can be seen as an
environmentally positive factor. However, the pos-
sibility of bacterial re-growth after the complete
degradation of the PAA cannot be discarded.
– The kinetics of degradation of PAA in the effluent
being studied indicated a first-order reaction, with
a half-life under 80 min.
– Even though the formation of by-products
(nonanal, decanal, chlorophenol, and 1-methoxy-
4-methylbenzene) was not observed with the ap-
plication of PAA in this effluent, more ample stud-
ies such as the formation of other possible by-
products and toxicity trials should be conducted
to guarantee the viability of the use of PAA.
– The results obtained in this study point to various
positive factors that would justify tests in pilot
scale, in which this disinfectant could be more
effectively monitored.
Table 4 Determination of some by-products of disinfection with PAA
By-products analyzed Effluent (TSS=38 mg/L)
Without PAA With PAA (10 mg/L)
Nonanal (mg C9H8O/L) <0.1 <0.1
Decanal (mg C10H20O/L) <0.1 <0.1
Chlorophenol (mg/L) 2.5 2.1
1-Methoxy-4-methylbenzene (mg/L) <0.1 <0.1
1752, Page 10 of 11 Water Air Soil Pollut (2013) 224:1752
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Water Air Soil Pollut (2013) 224:1752 Page 11 of 11, 1752
	Evaluation of the Physical–Chemical Characteristics of Wastewater After Disinfection with Peracetic Acid
	Abstract
	Introduction
	Materials and Methods
	Data Analysis
	Kinetic Trials of Degradation of PAA in the Effluent
	Determination of By-products Resulting from the Disinfection with PAA
	Results and Discussion
	pH Tests
	COD Tests
	DO Tests
	BOD Tests
	Some Factors that Influence the Consumption of PAA in the Effluent
	Kinetics of Degradation of PAA in the Effluent
	Determination of Possible By-products of Disinfection with PAA
	Conclusion
	References