Final Report
(March 16,2017)
Disinfection Pilot Trial for Little Miami WWTP
Cincinnati, OH October 17, 2016
Disclaimer:
This document has been prepared in accordance with the City of Cincinnati policy.
Any mention of trade names, commercial entities, or commercial products does not
constitute endorsement or recommendation for use.
The findings and conclusions in this report have not been formally disseminated by the
U.S. EPA and should not be construed to represent any agency determination or policy.
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Peracetic acid (PAA) was shown to provide effective bacterial reduction during field pilot
trialing at the Little Miami Wastewater Treatment Plant, located in Cincinnati, OH.
Reduction of both fecal coliform and E. colito below the permitted requirements was
demonstrated even at low PAA doses.
Key findings:
• A PAA dose rate of 1.0 mg/L and a contact time of 30 minutes were sufficient to
achieve the disinfection goal to reduce the geometric mean of fecal coliform to
below 200CFU/100 ml_, which is the current permit limit value for April to October.
The same dose rate and contact time were able to reduce the geometric mean of
E. coli to below 126 CFU/100 mL.
• A PAA dose rate of 0.5 mg/L and a contact time of 30 minutes were sufficient to
achieve the disinfection goal to reduce the geometric mean of fecal coliform to
below 1,000 CFU/100 mL, which is the current permit limit value for November to
March.
• At the effective doses of 1.0 mg/L and 0.5 mg/L, the residual PAA concentration
at the effluent discharge was always below 1.0 mg/L. As a result, it is anticipated
there will be no requirement to quench residual PAA prior to discharge, although the
Ohio Environmental Protection Agency (OEPA) has not yet set a specific discharge
limit.
• Whole Effluent Toxicity (WET) testing for composited samples, collected at PAA
dose concentration of 1.0 and 2.0 mg / L, resulted in "passing" performance, with
values for the TUa (acute toxicity unit) below detection for all the samples tested.
Proposed Next Steps:
Given the success of PAA in achieving the target microbial reductions, it is recommended
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that a full-scale field trial be conducted within the plants' disinfection contact
chambers to assess long-term performance under water quality and hydraulic flow
conditions experienced at the site.
This report and the conclusions herein are based on the data generated from the field
pilot test conducted at the Little Miami Wastewater Treatment Plant.
Project Team:
Dr. Achal Garg, Metropolitan Sewer District of Greater Cincinnati MSD, was the project
leader and supervised the planning and execution of the experiments.
Dr. Vasudevan Namboodiri, National Risk Management Laboratory (NRMRL), US
Environmental Protection Agency, Cincinnati, contributed during planning, execution, and
data analysis.
Dr. Kwok-Keung Au, PeroxyChem, participated in the planning and execution of the study,
data analysis and provided support to prepare the final report.
Page 3 of 27
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Disinfecting wastewater effluent is a critical final step in the treatment of wastewater. It
protects public health and the environment by inactivating disease-causing organisms
such as bacteria, viruses, and parasites. Various methods and technologies are used to
accomplish the goal of effluent disinfection. These include ultraviolet (UV) irradiation
(Carmineo et al., 1994; Lazarova et al., 1998; Kolch, 2000), ozone treatment (Lazarova et
al., 1998; Andreottola et al., 1996), and use of various chlorine derivatives (Hajenian &
Butler, 1980; Zanetti et al., 1996; Legnani et al., 1996). In the USA, wastewater effluent is
mainly disinfected by chlorine derivatives because of their wide spectrum of disinfection
efficiency and low treatment cost. Recent research, however, has evoked concerns about
effluent chlorination promoting the formation of toxic, mutagenic, and carcinogenic
properties in its disinfection by-products (DBPs). These harmful DBPs increase the
toxicity of the effluent that is discharged into water bodies with potential to cause harm to
the water quality and the environment (Dell'Erba et al. 2007; Kauppinen et al. 2012;
Veschetti et al. 2003).
Peracetic acid (PAA) is a strong oxidizing organic compound with a wide spectrum of
antimicrobial/biocidal properties similar to liquid chlorine or sodium hypochlorite (NaOCI).
It has been widely used in the food, beverage, medical, and pharmaceutical industries for
over 20 years (Kitis, 2004). Because of its strong antimicrobial properties, PAA has been
getting a lot of attention as a wastewater disinfectant to replace chlorine in recent years
(Lefevre et al., 1992; Baldry et al., 1995; Sanchez-Ruiz et al., 1996; Stampi et al., 2001,
2002; Wagner et al., 2002). It has been reported that PAA and sodium hypochlorite have
similar antimicrobial activities against E. coli, fecal coliform, and total coliform (Veschetti
et al., 2003); however, PAA holds multiple advantages over sodium hypochlorite as
disinfectant for wastewater effluent. These advantages include: need for lower doses,
lower residuals, faster disintegration, and absence of disinfection byproducts (DPBs) in
the treated effluent (Booth and Lester, 1995; Liberti and Notarnicola, 1999; Monarca et
al., 2000; Kitis 2004; Vaschetti et al., 2003; Crebelli et al., 2005; Koivunen & Heinonen-
Tanski, 2005; Antonelli et al., 2013).
The purpose of this study was to compare PAA and NaOCI disinfection efficiencies on the
secondary effluent in the lab and in a pilot study at the Little Miami Treatment Plant
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(LMTP) in Cincinnati, Ohio. The study was comprised of a series of lab experiments to
target fecal coliform and E. coli followed by a sidestream pilot scale study with the
following goals: (1) evaluate the suitability of PAA as a wastewater disinfectant for
secondary effluent by measuring the inactivation efficiency against target organisms, (2)
determine the dose and contact time necessary to keep the LMTP in compliance with the
National Pollution Discharge Elimination System (NPDES) requirements for fecal coliform
and E. coli discharge limits, and (3) assess the rate of PAA degradation by measuring
residual PAA in wastewater.
1.1 Objectives:
A pilot disinfection trial was conducted at the Little Miami Wastewater Treatment Plant
(WWTP) in Cincinnati, OH. The objectives of this trial were:
• To study the effectiveness of peracetic acid (PAA) to achieve compliance with the
wastewater discharges permit disinfection criteria for microbial indicators, fecal
coliform, and E. coli.
• To determine the operating conditions (PAA dose and contact time) required to
achieve such requirements.
• To assess the impact of PAA on the aquatic toxicity of the wastewater effluent.
The Little Miami Plant's current National Pollutant Discharge Elimination System
(NPDES) permit has requirements for fecal coliform not to exceed 200 CFU/100 mL
(monthly geometric mean) for April to October and not to exceed 1,000 CFU/100 mL
(monthly geometric mean) for November to March. These limit values were used as
the criteria to determine the target PAA dose rate and contact time required for
success during this trial. In addition, the disinfection performance against another
microbial indicator, E. coli, was studied in this trial. A limit value of 126 CFU/100 mL
for E. coli was used as the disinfection goal in this study. Note that a geometric mean
of 126 CFU/100 mL is a typical permit limit requirement in other States that use E. coli
as the indicator microbe in their NPDES permit.
1.2 Peracetic Acid:
PAA is a strong disinfectant that results from the equilibrium reaction between acetic
acid (vinegar) and hydrogen peroxide (H2O2). The PAA solution used in this
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study contains 15% peracetic acid (PAA) and 23% hydrogen peroxide (see Figure
1-1 for the chemical structure). The PAA molecule attacks and kills microbial
organisms of concern in wastewater treatment, such as fecal coliforms and E. coli
by disruption of cell membranes.
H
•C—C
v
Acetic Acid
/
H
O—Q
\
H
Hydrogen Peroxide
H
U—c—C
H
f J
\—o
Peracetic Acid
/
.0—H
H
Water
Figure 1-1 Chemical Structure of PAA
The oxidation potential of PAA is greater than that of hypochlorous acid, hypochlorite
ion and monochloramine (shown in Table 1-1), resulting in typically lower dosages and
contact times as compared to using chlorine or chloramines. In addition, PAA has a
much lower aquatic toxicity profile than chlorine and decays rapidly in the environment.
As a result, PAA generally does not need a quenching step, such as dechlorination,
reducing process complexity and cost. PAA is not a chlorine-based chemistry and
does not result in the formation of chlorinated disinfection by-products such as
trihalomethanes (THMs), and other byproducts such as cyanide and n-
Nitrosodimethylamine (NDMA).
Table 1-1 Standard Oxidation Potential (Kitis, 2004)
Oxidant
Standard Potential (V)
PAA (CH3COOOH)
1
Hyporchlorous Acid (HOCI)
1
Monochloramine (NH2CI)
1
Hypochlorite Ion (OCI")
0
2.1 Materials:
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The effluent samples were collected from the Little Miami wastewater treatment plant owned
by the Metropolitan Sewer District of Greater Cincinnati (MSD), Ohio, USA. Peracetic acid
(15%), marketed under the commercial name of VigorOX WWT II, was supplied by
PeroxyChem, Philadelphia, USA. PVS Chemical Solutions, Chicago, USA, supplied sodium
hypochlorite (NaOCI) (12%). E. coli and fecal coliform broth were obtained from Hach.
Buffered water with magnesium, micro filters, sampling bottles, and microbiological petri
dishes were from Thermo Fisher Scientific, Pittsburg, USA.
2.2 Methods:
Bench Study Experimental Set-Up
Grab samples of secondary effluents were collected to compare the disinfection efficiency of
PAA and NaOCI in the lab study. Samples of non-chlorinated raw effluent were collected in
sterile 100 milliliter plastic bottles and analyzed for fecal coliform and E. coli within 6 hours of
collection. To investigate the disinfection efficiency, the samples were treated with 2 to 7 ppm
doses of NaOCI or PAA for 10, 15, and 20 minutes. Membrane filtration method was used to
measure the efficiency of the treatment (Standard Methods, 22nd Ed., American Public Health
Association).
The PeroxyChem disinfection pilot reactor (DPR, Fig 3-1) was used in this pilot study.
Non-disinfected wastewater is fed into the DPR via a submersible pump, typically situated
within the effluent weir of the secondary clarifier. The flow rate through the DPR can be
adjusted to a maximum of 30 gallons per minute(gpm), and the effluent is discharged
back to the plant process stream prior to the final disinfection stage. A series of sampling
ports are located along the reaction section of the DPR. The combination of flow rate
through the DPR and selection of the sampling port allows for a wide range of contact
times to be simulated. PAA dosage at the head of the DPR is controlled via a metering
pump to achieve the desired target PAA dose concentration. As a result, microbial
reduction, PAA usage and water quality impacts can be assessed in the actual plant
wastewater under a variety of initial PAA dose concentrations and contact times.
Pilot Study Experimental Set-Up
The pilot study was conducted at the Little Miami Treatment Plant (LMTP) operated by the
Metropolitan Sewer District of Greater Cincinnati (MSD), Ohio. It is a secondary treatment
Page 7 of 27
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facility with an average flow of 25 million gallons per day (MGD).
Fig 3-1: Disinfection Pilot Reactor (DPR).
PAA Storage
Tank and
Flow
control
valves;
VI, V2
PAA Injection; SI
Treated
Effluent
Out
Submersible
Water Pump
,, Flow Meter
Pre-treatment
(raw) Sample
Port; R1
PAA Treated Sample
Collection Ports; P1-P6
Drain Flow
control
valve; V3
Effluent Drain
Effluent
Channel
¦0
Fig. 3-2
The pilot study was conducted on a Disinfection Pilot Reactor (DPR) (Fig. 1) owned and
supplied by PeroxyChem. The non-chlorinated secondary effluent was pumped into the reactor
through a submersible water pump. The effluent flow rate to the reactor was controlled using
three flow control valves (V1-V3). The flow rate was maintained at 15 gallons per minute (gpm)
throughout the period of the pilot study. The untreated control effluent sample was collected at
Page 8 of 27
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sample collection port (R1) downstream of PAA injection point. A PAA injection point (S1) was
located upstream of the flow meter and downstream of PAA treated sample collection ports
(P1-P6).
3.1 Trial Schedule
Data and sample collection of the PAA DPR field trial were started on June 6 and ended on
September 10, 2016. During this period, the DPR was completely operated by the LMTP
plant staff, which performed sample collection. All sample analyses were performed by
the Plant staff or laboratories selected by the Plant staff. Results were provided to
PeroxyChem on a routine basis. Close communication between Plant staff and PeroxyChem
staff was maintained during the trial period.
Figure 3-3 PAA Testing Dose during the Trial Period
3.2 Testing Flow Rate and PAA Dose
Non-disinfected secondary effluent was pumped into the DPR at a constant flow rate of 15
gpm during the sampling/data collection period. The PAA dose concentrations used during
the data/sample collection period is shown in Figure 3-3 and varied from 0.5 mg/L to 2.0
mg/L. The dose rate was adjusted as needed, mainly based on monitored results of fecal
coliform and E. coli in the final effluent. During the trial period, the Plant staff and
PeroxyChem staff reviewed testing data at least weekly and made necessary adjustment for
Page 9 of 27
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the PAA dosing rate.
3.3 Microbiological Analysis:
The effluent samples for microbial analysis were collected in 100 ml sterile plastic bottles
containing 10 mg sodium thiosulfate (Thermo Fisher Scientific, Cat# 05-719-361) for neutralizing
any residual PAA and H2O2 instantaneously. Each analysis was carried out on fecal coliform and
E. coli using a membrane filter. The fecal coliform colonies were counted after incubation for 24 ±
2 hours in a 44.5 ± 0.2°C water bath. E. coli plates were incubated for the same time in a 35 ±
0.5°C water bath (Standard Methods, 22nd Ed.).
3.4 Water Quality Monitoring:
The water quality monitoring plan is shown in Table 3-1 below.
Table 3-1 Water Quality Monitoring Plan for Little Miami VWVTP DPR Trial
Water Quality
Parameters
Sampling Location
Sampling
Frequency
Sampling
Type
Influent
(upstream
of VigorOx
Feeding
Point
Sampling
Port #3(2)
Sampling
Port #4(2)
Sampling
Port #6(2)
(final
effluent)
Fecal Coliform
(MPN/lOOmL)
V
V
V
V
Twice a Day
Grab
E. coli (CFU/lOOmL)
V
V
V
V
Twice a Day
Grab
PAA Residual(3)
NA
V
V
V
Twice a Day
Grab
Hydrogen Peroxide'4'
NA
V
V
V
Twice a Day
Grab
Chloride (mg/L)
V
NA
NA
NA
Twice a Day
Grab
Dissolved Oxygen (mg/L)
V
NA
NA
V
Once a Day
Grab
Ammonia (mg/L as N)
V
NA
NA
V
Once a Day
Grab
TSS (mg/L)
V
NA
NA
V
Weekly
Grab
cBOD5 (mg/L)
V
NA
NA
V
Weekly
Grab
pH
V
NA
NA
V
Twice a Day
Grab
Water Temperature (C)
V
NA
NA
NA
Twice a Day
Grab
Whole Effluent
Toxicity
NA
NA
NA
V
Once during
the Trial
In
accordance
to permit
Methodology.
(1) All samples were collected and measured by Plant staff or a laboratory selected by
Plant. Grab samples for different measurements were taken at the same time.
(2) At the test flow rate of 15 gpm, the corresponding contact time at port #3, #4 and #6
Page 10 of 27
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were 9 minutes, 17 minutes, and 30 minutes.
(3) PAA residual was measured using CHEMetrics V-2000 method. PeroxyChem provided
a handheld unit and associated training.
(4) Hydrogen peroxide was measured using a CHEMetrics 1-2016 Peroxide SAM unit.
PeroxyChem provided a handheld unit and associated training.
(5) Sampling bottles for fecal coliform and E. coli contained quenching agent to
neutralize any oxidant residual in the samples.
(6) Dilution of E. coli and fecal coliform samples was done as needed to obtain the exact
microbial count number.
(7) There was a minimum time gap of 3 hours between daily AM and PM samples. Every
time the test dose was changed, there was a minimum time gap wait of 2 hours before any
sample was taken.
4.1 Benchtop Lab Studies: Both lab studies and pilot project study show that PAA is as
effective as sodium hypochlorite (NaOCI) in disinfecting wastewater effluent. The bench top
studies were conducted in the lab as a precursor to the pilot study. The PAA efficiency was
compared with sodium hypochlorite at different doses and contact times on fecal coliform and E.
coli as target microorganisms. The microbial inactivation efficiency of both disinfectants was
measured between a 3 and 7 mg/L range. PAA was found to be significantly more effective at
lower doses of 3 and 4 mg/L concentrations compared to NaOCI. From 5 to 7 mg/L
concentrations, the difference between PAA and NaOCI efficiency was insignificant and showed
similar disinfection against fecal coliform and E. coli after 10, 15, or 20 min contact times. The
optimal microbial inactivation was achieved at 6 mg/L with PAA and NaOCI achieving between
4.5 and 5 log reduction. No additional bacterial inactivation was achieved by increasing the
doses to 7 ppm (Fig. 4-1).
Page 11 of 27
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1 NaOCI BPAA
Fig. 4.1 Berichtop Study: Comparison of NaOCI arid PAA Efficiencies on
E. coli in Secondary Effluent
¦ NaOCI
PAA
10 15 20
3 ppm
10 15 20
4 ppm
10 15 20
5 ppm
10 15 20
6 ppm
10 15 20
7 ppm
Fig. 4.2 Benchtop Study: Comparison of NaOCI and PAA Efficiencies on
Fecal coliform in Secondary Effluent
4.2 Side-stream PAA Disinfection Pilot Study: The disinfection efficiency of PAA
against E. coli and fecal coliform in the pilot project was dependent on the dose and
Page 12 of 27
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the length of contact time. Fecal coliform were found to be more sensitive to the
PAA's effect than E. coli. At PAA concentrations of 1.3 mg/L and 1.5 mg/L, a 1 log
reduction was achieved on fecal coliform after a 9 min contact time. In comparison,
only a 0.5 to 0.8 log reduction was observed in the number of E. coli bacteria when
exposed to 1.3 to 1.5 mg/L for 9 min contact time. The 2 mg/L concentration was
significantly effective against fecal coliform at 9 min showing a 1.8 log reduction in
fecal coliform compared with 1.3 and 1.5 mg/L for the same contact time. The highest
fecal coliform inactivation of 2.5 log reduction, was achieved at 30 min with 2 mg/L
concentration (Fig. 4.3) As for E. coli, there was a 1.8 to 2.3 log reduction depending
on the PAA concentrations (Fig 4.4).
3.0
2.5
2.0
1.5
W)
o
1.0
0.5
0.0
10.5 mg/L
1 mg/L
1.5 mg/L
2 mg/L
17
30
Contact time in min
Fig. 4-3 Log removal vs. Contact time with PAA in the pilot study: Fecal
Page 13 of 27
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3.0
2.5
Contact time in min
Fig. 4-3 Log removal vs. Contact time with PAA in the pilot study:
4.3 Influent Fecal Coliform and E. coli Concentrations
The fecal coliform and E. coli concentrations in the non-disinfected influent to the DPR
during the trial period are shown in Figure 4-5 and Figure 4-6, respectively. The horizontal
green and red lines in Figure 4-5 represent the seasonal permit limit values of fecal
coliform of 200 CFU/100 ml_ and 1,000 CFU/100 ml_, respectively. The horizontal red
line in Figure 4-6 represents the potential permit limit value of E. coli of 126 CFU/100 ml_.
Page 14 of 27
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PermitLimit: 1.000 CFU/100 ml
Permit Limit: 200 CFU/100 mL
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i i i
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vP-
Figure 4-5 Fecal Coliform Concentrations in Non-Disinfected Influent to DPR during
Trial Period.
100000
10000
1000
100
10
~~
~ ~
~ ~
~ %
PermitLimit: 126 CFU/100 mL
%
%
v»
Date
%
Figure 4-6 £. cofiConcentrations in Non-Disinfected Influent to DPR during Trial Period
The non-disinfected influent fecal coliform concentrations varied from 6,000 CFU/100 mL
to 230,000 CFU/100 mL, with a geometric mean of 29,933 CFU/100 mL. The non-
Page 15 of 27
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disinfected influent E. coficoncentrations varied from 6,000 CFU/100 mL to 72,000 CFU/100
mL, with a geometric mean of 22,191 CFU/100 mL.
Based on the non-disinfected influent fecal coliform levels, the log reductions required to
reduce fecal coliform concentrations to 200 CFU/m L and 1,000 CFU/100 m L were calculated.
The results are displayed in Figure 4-7. Similarly, the log reduction required to reduce E. cofi
concentrations to 126 CFU/100 mL was calculated and shown in Figure 4-8.
The results demonstrated that, depending on the influent concentration, a reduction from
1.48 logs (96.70%) to 3.06 logs (99.91%) was required to reduce fecal coliform to 200
CFU/100 mL during the trial period, based on single measurement. A reduction from 0.78
logs (83.50%) to 2.36 logs (99.56%) was required to reduce fecal coliform to 1,000 CFU/100
mL, based on single measurement. Similarly, a reduction from 1.68 logs (97.90%) to
2.76 logs (99.83%) was required to reduce E. cofi to 126 CFU/100 mL, based on single
measurement.
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Figure 4-7: Log Reductions Required to Inactivate Fecal Coliform to 200 CFU/100 mL and
1,000 CFU/100 mL.
Page 16 of 27
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• A PAA dose rate of 0.5 mg/L and a contact time of 30 minutes were sufficient to
achieve the disinfection goal to reduce the geometric mean of fecal coliform to
below 1,000 CFU/100 mL, which is the current permit limit value for November to
March.
• For peak flow condition (contact time of 17 minutes), a PAA dose of 2.0 mg/L
was required to reduce the geometric mean of fecal coliform to below 200 CFU/100
mL.A PAA dose of 1.0 mg/L was required to reduce the geometric mean of fecal
coliform to below 1,000 CFU/100 mL for peak flow condition.
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Figure 4-11 Fecal Coliform Concentrations at a contact time of 9 minutes.
Page 19 of 27
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Table 4-1 Statistical Summary of Fecal Coliform Concentrations
Contact
Time in
Minutes
Fecal Coliform at various PAA doses at different sampling locations
In CFU/100 mL (geomean)
Fecal Coliform Permit
Limits in CFU/100 mL
(geomean)
0.5 mg PAA/L
0.8 mg
PAA/L
1.0 mg PAA/L
1.5 mg PAA/L
2.0 mg PAA/L
April to
October
Nov to
March
30
633
1,368
117
112
102
200
1,000
17
8,458
4,805
400
324
137
9
19,194
7,123
2,818
2,314
464
Geomean vales were calculated based on the available data, rather than 30-day or
7- day results.
4-5 Disinfection Performance against E. coli
The disinfection performance against E. coli during the pilot trial is described in this
section. The E. coli concentrations measured at the influent and effluent of the DPR at
contact times of 30, 17 and 9 minutes are shown in Figure 4-12 (contact time 30 minutes),
Figure 4-1 3 (contact time 17 minutes) and Figure 4-14 (contact time 9 minutes). A statistical
summary of the effluent E. coli concentrations at different contact times under various PAA
doses is illustrated in Table 4-2.
The results, once again, demonstrated excellent PAA disinfection performance:
• As expected, the E. coli concentrations in the effluent decreased with increasing
PAA dose and increasing contact time.
• A PAA dose rate of 1.0 mg/L and a contact time of 30 minutes were sufficient to
achieve the disinfection goal to reduce the geometric mean of E. coli to below 126
CFU/100 mL.
• For peak flow condition (contact time of 17 minutes), a PAA dose of 2.0 mg/L
was required to reduce the geometric mean of E. coli to below 126 CFU/100 mL.
Page 20 of 27
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11.5mg/L
Omt'L
1.5mg/L
>
1.0me/L'0.5me/L
2.0mg/L
->
i *
V
~
~
~
- ~
*
~
~~
i
Q
O Q£> O
po°
<$>*--)
rermnLijiiii. i^bLru/iuu niL
; ~ Non-disinfected
Influent
—1—1—1—1—I—
O 30 min contact time
,—|—i—i—i—i—
PAA Dose
%
*b.
-------
100000
10000
1000
100
1
=
^5mg/L
I
^mg/Ll^g/Ll.Or
g^L 0.5mg/l^
^Omg/L
!«* *
! ~
~ ~
! ~
. 1 - *
«•»!» " *
! ~
- A
~
~
I
I
1
•• :
I
A *:
:A A
! A
* !
*•
!
E
a)
fl
L...
nit: 126 CfrU/100 mL
i
i
i
~
i nfluent
i
i
i
i
A
<5\.
<5\_
o>
<9
"w-
<5~
Date
V/
¦V.
o»
<5^
£>
•P,
"V
£>
Figure 4-13 E. coli Concentrations at a contact time of 17 minutes.
1000000
100000
10000
1000
=
1.5mg/L
>
2.0mg/L 1
>
5mg/Ll.(|
>
mg/L 0.5
ng/L
->
2.0mg/L
1 1 II MM
~~
V
i
~
~
«*
ff t ^
rn
~
1 II Mill
~
~
~
~
~
~
~
I n
r1
__A_61 .. . r .
Permit Limit: :
26 CFU/
100 mL
S 10
U 9 min contact time
%
&
%
7
Date
%
X>
(5s
Figure 4-14 E. coli Concentrations at a contact time of 9 minutes.
Page 22 of 27
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Table 4-2 Statistical Summary of E. colt Concentrations
Contact
Time in
Minutes
E. coli at various PAA doses at different sampling locations
In CFU/100 mi (geomean)
Potential Permit
Limit in CFU/100 mL
(geomean
0.5 mg PAA/L
1.0 mg PAA/L
1.5 mg PAA/L
2.0 mg PAA/L
30
656
125
91
81
126
17
16,764
789
636
103
9
19,971
4,640
3736
3,677
Geomean vales were calculated based on the available data, rather than 30-day or 7- day results.
4.6 PAA and Hydrogen Peroxide Residuals
PAA residuals in the final effluent of the DPR at the effective doses of 1.0 mg/L and 0.5 mg/L
during the trial period are shown in Figure 3-11.
0.8
0 .6
0.4
0.2
0
->
a
a
~ Dose of ±.0 mg/L
~ Dose of 0.5 mg/L
~
XI
(=P
~
-0+
->
->
Date
%
%
Figure 4-15 PAA Residuals in the Final Effluent of DPR at Effective Doses of 1.0 mg/L and 0.5mg/L
The site-specific discharge limit for PAA/total oxidants needs to be approved by the Ohio
Environmental Protection Agency (OPEA) before any use of this method for full scale field
trials. At present, we are involved in developing cost effective methods for the removal of
treatment residuals from the final effluent discharge.
Page 23 of 27
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0.8
0.6
00
E 0.4
& 0.2
~
~ Dose of 1.0 mg/L
~ ~
~ Dose of 0.5 mg/L
~
-J I I u
-J I I u
->
v.
V,
<9,
V,
V,
o,
^r.
<6-
Date
Figure 4-16 Hydrogen Peroxide Residuals in the Final Effluent of DPR at Effective Doses of
1.0 mg/L and 0.5 mg/L.
Hydrogen peroxide residuals in the final effluent of the DPR at the effective doses of 1.0
mg/L and 0.5 mg/L during the trial period are shown in Figure 4-1 6. The hydrogen
peroxide residuals were always less than 1.0 mg/L. Since the toxicity impact of hydrogen
peroxide on aquatic organisms was much lower than that of PAA, it is unlikely that it
is necessary to quench hydrogen peroxide before final discharge.
4.7 Whole Effluent Toxicity (WET)
Representative DPR effluent samples were collected for WET testing in accordance to
the protocol specified in the Little Miami WWTP's permit. Two sets of samples were
collected under the conditions shown in Table 4-3 for the WET testing. Note the samples
were taken under the PAA dosing conditions needed to achieve disinfection goals at the
average and peak flow situations, thereby representative of the average and the most
challenging conditions for potential toxicity impacts on aquatic organisms.
Page 24 of 27
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The samples were shipped to Great Lake Environmental Center (Columbus, OH) for static
acute toxicity testing using two aquatic organisms, Ceriodaphnia dubia, and Pimephales
promelas. The results demonstrated that, for both PAA-treated samples, the TUa (acute
toxicity unit) were below detection. This demonstrated that PAA technology could be
implemented as an environmentally friendly disinfection process at this facility, without
causing any compliance issue on WET or toxicity impact on the aquatic organisms of the
receiving stream.
Table 4-3 Sampling Conditions for WET.
Set of
Sample
Sampling Date
PAA Dose at
Sampling Date
mg/L
WET Testing Date
Started
Completed
#1
July 19, 2016
1.0
July 20 for both
organisms
July 22 for
Ceriodaphnia dubia,
July 24 for
Pimephales promelas
#2
August 15,
2016
2.0
August 16 for both
organisms
August 18 for
Ceriodaphnia dubia,
August 20 for
Pimephales promelas
Peracetic acid (PAA) was shown to provide effective bacterial reduction during field pilot
trials at the Little Miami Wastewater Treatment Plant, located in Cincinnati, OH.
Key findings:
• A PAA dose rate of 1.0 mg/L and a contact time of 30 minutes were sufficient to
achieve the disinfection goal to reduce the geometric mean of fecal coliform to
below 200 CFU/100 mL, which is the current permit limit value for April to October.
The same dose rate and contact time were able to reduce the geometric mean of
E. co//to below 126 CFU/100 mL.
• A PAA dose rate of 0.5 mg/L and a contact time of 30 minutes were sufficient to
achieve the disinfection goal to reduce the geometric mean of fecal coliform to
below 1,000 CFU/100 mL, which is the current permit limit value for November to
March.
• Whole Effluent Toxicity (WET) testing for composited samples, collected at PAA
Page 25 of 27
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dose concentration of 1.0 and 2.0 mg / L, resulted in "passing" performance, with
values for the TUa (acute toxicity unit) below detection for all the samples tested.
Proposed Next Steps:
Given the success of PAA in achieving the target microbial reductions, it is
recommended that a full-scale field trial be conducted within the plants' disinfection
contact chambers to assess long-term performance under water quality and hydraulic
flow conditions experienced at the site.
References:
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use. Zentralblatt fur Hygiene und Umweltmedizin 198, 552-566.
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wastewater reuse in agriculture. Water Sci Technol, 40:235-245.
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of different disinfectants on mutagenicity and toxicity of urban wastewater. Water Res., 34,
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efficiency and impact of raw wastewater disinfection with peracetic acid prior to ocean
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