The Impact of Commercially Treated Oil and Gas Produced Water Discharges on Bromide 

Concentrations and Modeled Brominated Trihalomethane Disinfection Byproducts at two 

Downstream Municipal Drinking Water Plants in the Upper Allegheny River, 

Pennsylvania, USA

Matthew S. Landis,

* Ali S. Kamal§

, Kasey D. Kovalcik, Carry Croghan, Gary A. Norris

US EPA, Office of Research and Development, Research Triangle Park, NC 27709

Amy Bergdale

US EPA Region 3, Office of Monitoring and Assessment, Wheeling, WV 26003

*

Corresponding author phone: (919) 541-4841; landis.matthew@epa.gov

§

Now at EPA Office of Air Quality Planning and Standards, Research Triangle Park, NC 27709

Abstract

In 2010, a dramatic increase in the levels of total trihalomethane (THM) and the relative 

proportion of brominated species was observed in finished water at several Western 

Pennsylvania water utilities (PDW) using the Allegheny River as their raw water supply. An 

increase in bromide concentrations in the Allegheny River was implicated to be the cause of the 

elevated water disinfection byproducts. This study focused on quantifying the contribution of

bromide from a commercial wastewater treatment facility (CWTF) that solely treats wastes from 

oil and gas producers and discharges into the upper reaches of the Allegheny River, and its 

impact on two downstream PDWs. In 2012, automated daily integrated samples were collected 

on the upper reaches of the Allegheny River at six sites during three seasonal two-week sampling 

campaigns to characterize bromide concentrations and river dispersion characteristics during 

periods of high (>8500 m3 min-1

) and low (<8500 m3 min-1) river discharge levels. The CWTF 

discharge resulted in significant increases in bromide compared to upstream baseline values in 

PDW raw drinking water intakes during periods of low river discharge. During high river 

discharge, the assimilative dilution capacity of the river resulted in lower absolute halide 

concentrations, but significant elevations bromide concentrations were still observed at the 

nearest downstream PDW intake over baseline river levels. On days with active CWTF effluent 

discharge the magnitude of bromide impact increased by 39 ppb (53%) and 7 ppb (22%) for low

and high river discharge campaigns, respectively. Despite a general declining trend in Allegheny 

River bromide (2009-2014), a significant impact of discharges from CWTF and coal-fired power 

plants to bromide concentrations during the low river discharge regime at downstream PDW 
intakes was observed, resulting in a small modeled increase in total THM (3%), and an estimated 

positive shift (41-47%) to more toxic brominated THM analogs.

Keywords: Specific Conductivity, Source Attribution.
Introduction

Elevated bromide (Br-

) levels in source water can lead to the formation of higher levels of 

brominated disinfection byproducts (DBP) in finished drinking water; currently, conventional

drinking water treatment processes do not effectively remove Br- from source water (States et al., 

2013). In 2010 the Pittsburgh Water and Sewer Authority (PWSA) observed significantly 

increased concentrations of total trihalomethanes (THM; a group of regulated DBPs) in their 

water distribution system that were near the regulatory limit of 80 ppb (U.S. EPA, 1998), and 

found the proportion of brominated THM species to be substantially higher than normal (States 

et al., 2013). Six additional drinking water companies relying on the Allegheny River as their 

source of raw water had their finished water tested and elevated levels of total and brominated 

THM concentrations were also found, suggesting that the concentration and chemical makeup of 

the THMs were changing in response to increased Br- concentrations in the river source water 

(States et al., 2013). Brominated DBPs are of particular concern to public health authorities 

since they are more carcinogenic, cytotoxic, and genotoxic than their chlorinated DBP analogs 

(WHO, 2000; Plewa et al., 2002; Richardson et al., 2007), from consumption, inhalation during 

showering, and dermal exposure (Cantor et al., 2010; Font-Ribera et al., 2010; Kogevinas et al., 

2010; Richardson et al., 2010). Discharges of treated oil and gas well produced wastewater and 

commercial coal-fired power plants have been implicated as the primary sources of excess Br- in 

both the Allegheny and Monongahela rivers in Western Pennsylvania (States et al., 2013; 

Warner et al., 2013; Wilson and VanBriesen, 2013). Naturally occurring brine in the 

hydrocarbon rich formations in the Appalachian Plateau in Western Pennsylvania leads to 

elevated Br- and chloride (Cl-

) concentrations in the oil and gas produced wastewater (Dresel and 

Rose, 2010; Haluszczak et al., 2013). These elevated levels of Br- and Cl- being discharged into 

the Allegheny River have raised concerns of many Western Pennsylvania water suppliers over 

their ability to comply with the U.S. Environmental Protection Agency (EPA) Stage 2

Disinfectant/Disinfection Byproduct Rule (2006) amending the sampling and quarterly DBP 

calculation methodologies with compliance beginning in 2012 for the largest systems.

The large national increase in exploration, drilling, and production of oil and gas from nonconventional shale resources has generated large volumes of additional wastewater that 

ultimately needs to be reused/recycled or disposed (Kargbo et al., 2010; Gregory et al., 2011; 
Vidic et al., 2013). Most oil and gas well wastewater is disposed through deep well injection in 

many parts of the U.S. (Gregory et al., 2011). However, in Pennsylvania, there is currently a

limited capacity for deep well injection with only eight EPA approved Class IID brine disposal 

wells, and the development of the Marcellus Shale has increased the total wastewater generated 

in the region by ~570% since 2004 (Lutz et al., 2013). The majority of oil and gas well 

wastewater that is not reused is either trucked out of state for deep brine disposal well injection 

or disposed of using alternative methods (Veil, 2010; Wilson and VanBriesen, 2013).

In Pennsylvania, the first Marcellus Shale gas well was drilled in 2004 (PA DCNR, 2014). 

Through March 9, 2012 the Pennsylvania Department of Conservation and Natural Resources

issued 11,772 permits for non-conventional wells in the Marcellus Shale, of which 1,456 well 

completion reports were received (PA DCNR, 2014). Overall, the number of gas producing

wells increased in Pennsylvania from 46,654 in 2005 to 55,136 in 2012 (U.S. EIA, 2014). 

Historically, Pennsylvania has allowed oil and gas produced wastewater to be discharged into

publicly owned sewage treatment works (POTWs) where it was diluted, or treated by 

commercial wastewater treatment facilities (CWTF) that solely treat wastes from oil and gas 

producers with subsequent discharge to surface waters (Veil, 2010; Lutz et al., 2013). Most 

CWTFs are designed to chemically precipitate, flocculate, and filter solids; but are not designed 

nor successful in removing dissolved monovalent halides like Br- and Cl- (Ferrar et al., 2013; 

Warner et al., 2013). In 2011 the Pennsylvania Department of Environmental Protection

(PADEP) issued a letter to oil and gas producers requesting that they voluntarily discontinue 

using POTWs and CWTFs to dispose of Marcellus formation wastewaters (PA DEP, 2011), 

which accounted for 79% of gas-related wastewater in Pennsylvania that year (Vidic et al., 

2013). All indications suggest that the producers have complied and diverted Marcellus derived 

wastewater to other reuse or disposal options (Wilson and VanBriesen, 2013). However, other 

non-Marcellus Devonian unit oil and gas wastewaters continue to be sent to both POTWs and 

CWTFs that ultimately discharge to surface waters (Vengosh et al., 2014; U.S. EPA 2015). The 

concentrations of Br- and Cl- in the upper Devonian well brines have been reported to be as high

or higher than the Marcellus wastewater (Dresel and Rose, 2010; Warner et al., 2013).

The Allegheny River is a vital natural resource to residents of Western Pennsylvania. Among its 
provisioning services are accepting waste discharge and supplying drinking water. There is a 

delicate balance between these services, especially during low river discharge periods when the 

river’s assimilative capacity to dilute contaminant concentrations down to safe levels is 

diminished (Ferrar et al., 2013). The Allegheny watershed is vulnerable to impairment due to 

current discharges from POTWs, CWTFs, coal-fired power plants, iron and steel production, 

manufacturing, urban runoff, roadway deicing materials, ongoing coal mining activities, legacy 

mine discharges, and acid rain (Schofield 1982; PA DEP 2002; Wilson and VanBriesen, 2013). 

The water quality at the intakes for public drinking water systems (PDW) is degraded by these 

upstream discharge sources, and concern over this balance is heightened due to perceived 

impacts from increased oil and gas drilling activities (States et al., 2013). Many of the sources of 

impairment to river water quality have distinctive chemical characteristics, discharge at different 

spatial locations, and are variable in time (U.S. EPA 2015). To manage these valuable watershed 

services, investigative tools and strategies that exploit these unique discharge properties are 

needed that track and quantitatively apportion discharge source impacts on surface water quality.

This study’s goals were to (i) establish an approach whereby the impact of a surface water 

discharge from a CWTF in the upper reaches of the Allegheny river on the raw water halide 

concentrations at the nearest downstream PDW could be quantitatively evaluated, and (ii) to 

estimate the impact of CWTF discharges on total THM concentrations and the relative 

abundance of brominated DBPs in finished drinking water at two PDWs on the Allegheny River 

using empirical EPA models.

Methods

Study Design

In 2012, U.S. EPA conducted three seasonal two-week sampling campaigns: spring (April 30-

May 14), summer (July 5-19), and fall (September 19-October 4) on the upper Allegheny River

in Pennsylvania. Samples were simultaneously collected from an upstream location (S01-

Upstream), a CWTF discharge (S02-CWTF), two downstream locations (S03-Downstream1 &

S04-Downstream2), and two downstream PDW raw water intakes (S05-PDW1 & S06-PDW2;

Figure 1) using automated samplers. The CWTF was accepting, treating, and discharging nonMarcellus Appalachian Plateau Devonian strata oil and gas produced wastewater during all 
sampling campaigns. The upstream sampling location was to establish “baseline” conditions

into the study domain, and the multiple downstream sampling locations were to evaluate 

transport and dispersion of inorganic species discharged by the CWTF to the closest downstream 

PDW. The Allegheny River mile of each site and their relative distance from the CWTF 

discharge is presented in Appendix A.1. The first sampler downstream of the CWTF discharge 

was located ~12 km downstream to allow for adequate initial mixing of the effluent and river 

water. The second downstream sampler was located between the first downstream sampling 

location and the closest PDW intake, and was located ~15 km downstream of an 85 megawatt

bituminous waste coal-fired power plant discharge. The second PDW plant was included to 

investigate the general trend of increasing Br- concentrations in the Allegheny as it traverses 

from the upper into the lower reaches of river.

Allegheny River

The Allegheny River drains a catchment area of approximately 30,300 km2 in the Pennsylvania 

and New York region of the northwestern Appalachian Plateau (PA Fish and Boat Commission, 

2011). Most reaches of the upper Allegheny flow over locally-derived river sediment overlying 

thick layers of glacial outwash (sand and gravel). The Allegheny headwaters flow into the 

Allegheny Reservoir and leaves via the Kinzua Dam. Approximately 203 km of the Allegheny 

River downstream of the Kinzua Dam, including the entire upper Allegheny study domain (S01-

Upstream to S05-PDW1), remains free-flowing; and is confined within a narrow, severely 

meandering valley with precipitous side slopes (PA FBC, 2011).

Further downstream, the Allegheny is impounded and regulated by the U.S. Army Corp of 

Engineers (USACE). The USACE manages the water level of the Allegheny in the study 

domain by controlling water discharge volumes from the Kinzua, Tionesta, Union City, and 

Woodcock reservoirs (USACE, 2014). This active management provides for flood control, 

water quality management, and downstream navigation requirements. The water levels in the 

upper reaches of the Allegheny River below the Kinzua Dam have historically been (i) highest in 

the late fall and winter during reservoir drawdown in preparation for snow melt and spring

precipitation, resulting in a relatively high assimilative capacity from source discharges, and (ii) 

lowest in the summer resulting in elevated concentrations of contaminants (USGS, 1993; USGS, 
2013). Due to the resulting annual bimodal nature of Allegheny River water discharge rates, our 

data analysis is categorized into “high” (≥ 8500 m3 min-1) and “low” discharge (<8500 m3 min-1)

regimes (USGS, 1993).

Sample Collection

Teledyne Isco (Lincoln, NE) Model 6712 computer-controlled automatic sequential water 

samplers were utilized to simultaneously collect daily 800 ml composite river, CWTF, and PDW 

samples along the Allegheny River study domain. Acid-cleaned (Landis and Keeler, 1997)

polypropylene bottles and Teflon sampling line were used to minimize contamination from the 

sampler. The samplers were programmed to collect 400 ml twice a day at 09:00 and 12:00 EST, 

after automatically rinsing the sampling line three times. The river sampler inlets were 

positioned as far away as possible from vegetation and eddy currents near the river banks, and 

~15 cm off the river bed. Isco sampler inlet distance from the river banks ranged from 3.1-4.1 m 

during the high river discharge campaign, and 4.6-15.3 m during the low river discharge 

campaigns. Isco sampler inlet depths from the surface ranged from 46-71 cm during the high 

river discharge campaign, and 15-66 cm during the low river discharge campaigns. Sample 

bottles were retrieved every 2-4 days. Grab samples were also collected from the POTW and 

coal-fired power plant (CFPP) in the study domain using acid-cleaned polypropylene dippers and 

poured into sample bottles. Ultra-clean handling methods for sample deployment and collection 

were employed to avoid contamination of the collected samples (Landis et al., 2002). All 

collected samples were packed in ice and shipped overnight to the laboratory.

Conductivity

Onset (Cape Cod, MA) HOBO Model U24-01 in-river sondes were deployed to measure 

temperature and electrical conductivity at each of the Isco sampling sites at 5 min intervals. A 

YSI (Yellow Springs, OH) Model 556 multi-parameter instrument was utilized to collect 

traceable temperature compensated specific conductivity (SC) readings to scale each Onset inriver sonde using manufacturer provided HOBOware® Conductivity Assistant software

(Appendix A.2). The YSI instrument was calibrated each morning using YSI-3161 1000 μS cm-1

standard solution, checked again each night, and checked weekly using YSI-3165 100000 μS cm1 standard solution. Daily calibration check precision (n=42) was 98 ± 2% (mean ± standard 
deviation), and the weekly high range linearity check precision (n=9) was 95 ± 4%. A collocated 

Onset in-river sonde was deployed at S03-Downstream1 and the collocated precision (n=16685) 

was 98 ± 3%.

Specific conductivity of Isco samples was determined in an EPA Class 100 clean room using a 

Mettler Toledo (Columbus, OH) Model S47-K meter equipped with an InLab®731 probe. A two 

point calibration curve was generated each day using certified Mettler Toledo 1413 μS cm-1 and 

12.88 mS cm-1 conductivity standards. Accuracy checks were conducted using a Ricca Chemical 

(Arlington, TX) 1, 50, 100, and 200 mS cm-1 certified secondary standards to ensure linearity. 

Replicate analysis was performed on a minimum of 10% of samples and the observed precision 

(n=54) was 99 ± 1%, and collocated sample precision (n=123) was 98 ± 5%. The mean of the 

two five-min Onset in-river conductivity data points corresponding to the two daily Isco 

sampling times were compared to the Isco sample conductivity and the relative precision was 

found to be 93 ± 10% (Appendix B.1).

Major Anions

Anions were quantified using a Dionex (Sunnyvale, CA) Model ICS-2000 ion chromatography

instrument following an optimized U.S. EPA Method 300.1 (US EPA, 1997) technique as 

described below. Each sample was injected twice to evaluate analytical precision. Anion 

separations were performed with a 200 μL sample loop injection onto a Dionex IonPac© AG18 

(4x50mm guard) and AS18 (4x250mm analytical) cation-exchange column, utilizing an isocratic 

potassium hydroxide eluent method. The analytical columns used met performance criteria 

specified in U.S. EPA Method 300.0 (1993). The ICS-2000 instrument was externally calibrated 

using a six point curve generated from a mixed Dionex seven anion standard (#057590). Initial 

calibration verification was performed with secondary source standards (High Purity Standards, 

Charleston, SC) and NIST (Gaithersburg, MD) Standard Reference Materials for Cl- (#3182) and 

Br- (#3184). Calibration stabilities were verified daily by mid-level continuing calibration 

verification samples. Linear calibration curve statistics were verified with minimum acceptance 

criteria of a coefficient of determination (r

2

) > 0.999. In order to increase the linear dynamic 

range, two analytes (sulfate (SO4

2-

), Br-) were processed with a quadratic regression, utilizing 

seven calibration points with minimum acceptance criteria of r

2 > 0.99. Prior to injection, all 
field samples were filtered using Millipore (Billerica, MA) IC-Millex syringe filters (25mm, 

0.45μm PTFE). Each chromatogram was visually verified for peak shape, retention and 

identification. CWTF samples were all diluted 1000x with ASTM Type I ultra-pure water (18.2 

MΩ⋅cm) prior to analysis. Replicate analysis was performed on ~10% of all samples and the 

resulting analytical precision ranged from 99 ± 2% (Br-) to 100 ± 1% (Cl-, SO4

2-

). Collocated 

samples were collected and analyzed for ~30% of all observations and the resulting precision 

ranged from 96 ± 10% (SO4

2-

) to 99 ± 2% (Cl-). A summary of all analyte specific instrument 

detection limits, method detection limits, and analytical/collocated precision are presented in 

Appendix A.3.

USGS River Gage Data

River water discharge volumes for the sampling domain were obtained from the U.S. Geological 

Survey (USGS). Hourly discharge data is available from October 1, 2007 through 2014 (USGS, 

2015) for gage station #03025500 (Franklin, PA) located 1.5 km upstream of site S01-Upstream

on the Allegheny River, and gage station #03031500 (Parker, PA) located 11 km downstream of

S05-PDW1. The Parker gage station is located 1.8 km downstream of the Clarion River

confluence. The water discharge contribution from the Clarion River as measured by gage 

#03030500 (Piney, PA) was subtracted from the gage value downstream of S05-PDW1 to 

estimate river discharge closure within the upper Allegheny River sampling domain (Appendix

B.2).

Categorization of CWTF Discharge Impacted Samples

The non-continuous operation schedule of the CWTF resulted in periods with and without 

discharge. High time resolution (5 min) in-river sonde conductivity data from each of the 

sampling sites clearly elucidated defined CWTF conductivity discharge plume tracer events as 

they were transported and hydrologically dispersed downstream through the upper Allegheny 

River sampling domain. Transit time analysis was performed independently between the 

CWTF-P45 (45 m downstream of the discharge pipe) and each downstream site, similar to 

conducting a dye or tracer study in the river (Smart and Laidlaw, 1977; Kunkel and Radke, 

2011). An example site-to-site transit time analysis of the CWTF discharge conductivity plumes 

to the 12.2 km downstream site S03-Downstream1 from September 24-29, 2012 is presented in 
Figure 2. The example transit times (∆t) defined as the CWTF median discharge time to the 

maximum downstream conductivity value were ~16 hours during this period, and are depicted as 

dropdown lines in Figure 2. Figure 3 depicts the CWTF-P45 and S03-Downstream1 site 

conductivity data example after the ∆t = 16 hour plume transit time adjustment, showing the 

conductivity peaks observed at site S03-Downstream1 align with the CWTF discharge times

(drop down lines represent the programmed Isco sampling times). Transit times were calculated 

independently for each sampling site during each seasonal sampling period.

Based on these empirically derived plume transit times to each of the downstream sites and the 

duration of the CWTF discharge, all Isco samples were categorized as “discharge impacted” if 

one or both of the sample collection times (9:00 and 12:00 EST) fell within the conductivity 

plume impact time for each site. Based on the transit time analysis Isco samples from the 

example time period: September 24-28 and September 29 were categorized as “impacted” and 

“non-impacted”, respectively. Each Isco sample and its associated time corrected in-river sonde 

conductivity data was visually evaluated to ensure accurate categorization. S06-PDW2 site was 

too far down stream to track the CWTF discharge conductivity plumes and was therefore not 

included in the intra-site analysis.

Disinfection Byproduct Empirical Modeling

Empirical modeling of DBP formation in PDW was conducted to estimate the impact of 

additional Br- contributed by CWTF discharges on total THM and brominated analogs at two 

downstream intakes. The EPA empirical models employed (U.S. EPA, 1998; Solarik et al., 

2000) are statistically-based and were developed by EPA for predicting DBP formation during 

water treatment disinfection using chlorine and ozone. Each model was formulated through 

multiple step-wise regression analysis and takes the form of a multiple regression equation. 

While the predictive empirical models may not accurately predict the complex conditions at any 

particular PDW (Brown et al., 2011) they are considered to generally descriptive and useful for 

the evaluation of water treatment facilities and human risk assessment (Sadiq and Rodriguez, 

2004; Chowdhury et al., 2009). Different versions of the model were evaluated based on their 

ability to predict the reported THM concentrations at PDW1 and PDW2 during our sampling 

periods. Model input parameters are presented in Appendix Table A.4. Due to the use of 
prechlorination, the raw water version of the THM prediction model provided the best predictive 

results for both PDW1 and PDW2, and was utilized for all subsequent analysis. Based on 

median raw water Br-, temperature, and pH measurements made during this study and PADEP 

organic carbon measurements available for 2012-Quarter 2 (Q2) and 2012-Q3 at a location ~28

km upstream of PDW1 (PADEP, 2014; ), the model predicted 2012-Q2 (high river discharge 

regime) total THM to be 50 ppb versus an actual reported concentration of 68, and the model 

predicted 2012-Q3 (low river discharge regime) THM to be 107 ppb versus an actual reported 

concentration of 110 ppb.

EPA’s empirical raw water DBP model was also run for PDW2 using the median raw water Br-, 

temperature, and pH measurements made during this study and PADEP organic carbon 

measurements available for 2012-Q2 and 2012-Q3 at a location ~25 km upstream (PA DEP, 

2014). The model predicted 2012-Q2 (high river discharge regime) THM to be 47 ppb versus an 

actual reported THM concentration of 53, and the model predicted 2012-Q3 (low river discharge 

regime) THM to be 99 ppb versus an actual reported THM concentration of 101 ppb. Based on 

the reasonable results of the raw water model, it was used to estimate the impact of the Brconcentrations attributed to CWTF discharges on PDW THM concentrations.

Statistical Analysis

Data processing and all statistical analyses were performed using SAS v.9.4 (SAS Institute, 

Cary, NC). Parametric statistics used in this analysis include: a t-test for independent samples, 

and one-way analysis of variance (ANOVA). The assumptions of the parametric procedures 

were examined using residual plots, skewness and kurtosis coefficients, Shapiro-Wilk test, and 

the Brown-Forsythe test. If assumptions of the parametric procedures were violated, then the 

Wilcoxon and Kruskal-Wallis non-parametric procedures were used, respectively. Analytical

and collocated precision were calculated as 1-(absolute percent difference) for replicate and 

collocated sample analysis, respectively. In order to determine which combination of major 

anions best predicts conductivity, the results, which were first obtained using stepwise regression 

glmselect procedure, were verified using the general linear model sums of squares and Spearman 

correlation matrix. One-sided tests and a level of significance of α=0.05 was used for all 

statistical procedures unless otherwise stated.
To determine if the CWTF discharge significantly increased halide concentrations at downstream 

sampling sites, the downstream Isco samples were evaluated by both intra- and paired inter-site 

statistical hypothesis tests. The downstream inter-site “discharge impacted” Isco samples were 

paired with their associated transit time corrected S01-Upstream sample. During the spring high 

river discharge measurement intensive, S03-Downstream1 Isco samples paired with S01-

Upstream Isco samples on the same day while S01-Upstream Isco samples paired with S04-

Downstream2 and S05-PDW1 Isco samples on the following day. During low river discharge 

measurement intensives in the summer and fall, S03-Downstream1 Isco samples were lagged by 

one day whereas S04-Downstream2 and S05-PDW1 Isco samples were lagged by two days with 

their paired S01-Upstream sample.

Upper Allegheny Mass Balance Model

A box model detailing daily river baseline and source discharge loading was developed to 

investigate the dilutive capacity of the river in our study domain and to evaluate the estimated 

CWTF impact on Br- and Cl- at downstream S05-PDW1 based on the inter- and intra-site 

comparison method. Daily river baseline loadings were calculated as the product of the river 

volumetric flow and the S01-Upstream river concentration. Source discharge contributions from 

S02-CWTF were calculated as the product of the facility reported daily discharge volumes and 

the daily EPA sample concentrations. Source loading from the POTW and CFPP (without flue 

gas desulfurization (FGD) scrubbers) in the study domain (Figure 1) were calculated using the 

mean EPA discharge grab sample concentrations and facility reported monthly discharge volume 

(adjusted to daily discharge volume). The water volume closure of the box model in the upper 

Allegheny River study domain was evaluated using the results calculated using Equation 1

(Appendix B.2).

CCCCCCCCCCCCCC (%) = 100 − ��

PPPPPPPPPPPP GG GG − (FF FF FFFFFF GG GG + CC CC RR RR GG GG )

PPPPPPPPPPPP GG GG � ∗ 100� (1)

Results and Discussion

Monitoring Campaign Allegheny River Conditions
The river flow conditions and CWTF wastewater discharge characteristics during the sampling 

campaigns were evaluated to see if they were generally representative of overall 2012 conditions. 

A non-parametric Wilcoxon Two-Sample Test, found no significant difference between the 2012 

daily mean Allegheny River high discharge period volumes (25,246 ± 12,067 m3 min-1

; p=0.56) 

and the discharge volumes during the study campaign sampling period (25,477 ± 3,880 m3 min-1

; 

Appendix B.3a). However, the Wilcoxon two-Sample Test did find a significant difference 

between the 2012 daily mean Allegheny River low discharge period volumes (5,059 ± 1082 m3

min-1; p=0.05) and the discharge volumes during the study campaign sampling period (4,591 ± 

566 m3 min-1

; Appendix B.3b). When evaluating the 2012 Allegheny River discharge volumes 

to the available daily historical records (2007-2014), we found the 2012 high river discharge 

period volumes to be consistent with the average values (25,266 ± 11,575 m3 min-1

; p=0.56; 

Appendix B.3a) but the low discharge rates were found to be significantly lower than the 

historical average (4,977 ± 1,025 m3 min-1; p<0.001; Appendix B.3b) due to a summer drought.

The median CWTF treated wastewater discharge volumes from April 2 - October 31, 2012 

(n=157) was 333,976 liters per operation day with a range of 8,210 - 750,269 liters. The median 

CWTF discharge volume during the monitoring campaigns was (n=38) 245,696 liters per 

operation day with a range of 9,017 - 676,075 which was not significantly different from the 

overall period (Wilcoxon Two-Sample Test p=0.06). The facility indicated its discharge 

volumes were a function of customer demand for brine treatment services and facility 

operational conditions.

Upper Allegheny River Observations

The overall study conductivity and halide results are generally consistent with previous 

observations (States et al., 2013), which demonstrate that background levels in the upper 

Allegheny River are relatively low and significantly increase downstream. When the high and 

low river discharge regimes are examined independently (Table 1), the assimilative dilution 

capacity of the river during periods of high discharge is evident for halide species and results in

significantly (p<0.001) lower conductivity, Br-

, and Cl- at each of the sites. The median domain 

baseline conductivity (126 μS cm-1), Br- (25 ppb), and Cl- (13.1 ppm) at S01-Upstream during 
the spring high river discharge campaign were lower than the corresponding medians of 174 μS 

cm-1, 72 ppb and 21.0 ppm during the combined summer/fall low river discharge campaigns. 

The median S05-PDW1 conductivity (158 μS cm-1), Br- (38 ppb) and Cl- (17.0 ppm) during the 

high river discharge campaign increased to 202 μS cm-1, 85 ppb and 23.5 ppm, respectively, 

during the low river discharge campaigns. While the overall halide concentrations were lower 

during the high discharge spring campaign, the S05-PDW1 site downstream of the CWTF 

discharge in our study domain was significantly higher than S01-Upstream baseline site for 

conductivity, Br-, and Cl-.

Lower Allegheny River Observations

While not in the upper Allegheny River study domain, comparing the results observed at S06-

PDW2 ~100 km further downstream from S01-PDW1 is informative to evaluate the integrative 

impact of additional downstream sources in the watershed on another public drinking water 

resource (U.S. EPA, 2015; Appendix B.4a-c). Significant increases in conductivity, Br-

, Cl-, and 

SO4

2- were observed between S05-PDW1 and S06-PDW2 during the low river discharge 

campaigns, and significant increases in conductivity, and SO4

2- were observed during the high 

river discharge campaign (Table 1; Appendix B.4a-d). On an integrated basis during the high 

river discharge campaign, there was a 154% increase in SO4

2- (11.3 to 28.7 ppm), a 16% increase 

in conductivity (157 to 182 μs cm-1), a 3% decrease in Br (36 to 35 ppb), and an 8% decrease in 

Cl- (17.3 to 15.9 ppm) from S05-PDW1 to S06-PDW2. During the low discharge campaigns 

there were significant increases (Table 1; Appendix B.4a-d) in all contaminant concentrations at 

S06-PDW2 relative to S05-PDW1 including a 754% increase in SO4

2- (9.6 to 82.0 ppm), a 83% 

increase in conductivity (204 to 374 μs cm-1

), a 63% increase in Br- (87 to 142 ppb), and a 29% 

increase in Cl- (23.6 to 30.4 ppm). A step-wise multi-linear regression analysis found that 

conductivity at S01-Upstream and S06-PDW2 were best predicted by Cl- and SO4

2- (R2 = 0.965),

while conductivity at S03-Downstream1, S04-Downstream2, and S05-PDW1 were best 

predicted by Cl- and Br- (R2 = 0.862). This finding indicates that in the upper reaches of the 

Allegheny River (S03-Downstream1 to S05-PDW1) downstream of the CWTF discharge 

conductivity is halide dominated, whereas in the lower reaches of the Allegheny River (S06-

PWD2) it reverts back to a more SO4

2- dominated system.
The distance, tributary inflow (Appendix B.2), and additional anthropogenic discharge sources 

downstream of S05-PDW1 preclude identification of the source types contributing to the 

elevated concentrations at S06-PDW2 within the context of this work. One indication that coalrelated sources are substantially impacting halide concentrations at S06-PDW2 is the large 

increase in SO4

2-

(Table 1) in combination with a downward shift in the Cl-/Br- ratio in relation to 

the upper Allegheny River study domain (Appendix B.5). During the low river discharge

campaigns the median Cl-

/Br- drops from 278 (S05-PDW1) in the upper Allegheny River study 

domain to 217 (S06-PDW2) suggesting an impact from a characteristically lower Cl-

/Br- source 

such as upper Pennsylvanian Conemaugh and Monongahela formation bituminous coals that are 

mined regionally (Seere and Lee, 2009; U.S. EPA, 2015).

Impact of CWTF on S05-PDW1 Raw Water

The operation schedule of the CWTF during the study campaigns, nominally 06:00-13:00 EST

Monday through Friday, allowed us to investigate downstream river conditions both in the 

presence and absence of treated oil and gas wastewater discharge. During both the high and low 

river discharge campaigns, the automated samplers captured a sufficient number of CWTF 

discharge impacted and non-impacted categorized samples at the S03-Downstream1, S04-

Downstream2 river sites, and S05-PDW1 intake for inter- and intra-site statistical analyses. A 

summary of the high and low river discharge regimes CWTF impacted and non-impacted 

categorized data and inter-site paired Kruskal-Wallis one-sided test results are presented in 

Tables 2 and 3, respectively.

Evaluating the impact of the S02-CWTF discharge on downstream sites can be characterized on 

an inter-site basis by evaluating the S01-Upstream conductivity and anion species means versus 

the downstream site means for those species that were found to have no significant sources in the 

study domain other than the CWTF discharge. In this case we define no other significant source 

impacting the PDW intake as a condition whereby (i) the non-discharge impacted categorized 

samples at S05-PDW1 and their paired S01-Upstream site samples are not significantly different 

during both high (Table 2) and low (Table 3) river discharge conditions and (ii) no significant 
contribution from the POTW and CFPP discharge grab samples, only Br- meets this criterion. 

During both the high (Table 2) and low (Table 3) river discharge sampling periods the observed 

Br- concentrations at S03-Downstream1, S04-Downstream2, and S05-PDW1 raw drinking water 

intake were not significantly different than the paired S01-Upstream Br- concentrations during 

non-discharge impacted days, but were significantly higher during CWTF discharge impacted 

days. These relationships for the Allegheny River low discharge regime are clearly depicted in 

Figure 4a where the stable Br- concentrations throughout the study domain during non-CWTF 

discharge days are contrasted with the clearly observable downstream enhancement during 

discharge days, which was initially highest at the S03-Downstream1 site with decreasing

concentrations as a result of dilution and hydraulic dispersion downstream to S05-PDW1. This

inter-site analysis takes into account the periods of CWTF discharge only and provides a 

quantitative overall estimate of Br- enhancement through the study domain. The magnitude of 

the integrated Br- enhancement during low river discharge from the CWTF on downstream sites 

was 109% (81 ppb) at S03-Downstream1, 45% (33 ppb) at S04-Downstream2, and 51% (38 ppb) 

at S05-PDW1. During high river discharge the integrated Br- enhancement on downstream sites 

was 50% (14 ppb) at S03-Downstream1, 31% (8 ppb) at S04-Downstream2, and 50% (13 ppb) at 

S05-PDW1. At first glance the lower relative impact of the CWTF effluent discharge on 

observed Br- concentrations at the S03-Downstream1 site during the high river discharge period 

seemed to suggest that the Allegheny River’s assimilative capacity was adequate to dilute CWTF 

related contaminants down to lower relative levels within the 12 km distance between the 

discharge and the site. However, when we evaluated the Isco sampling times categorized as 

CWTF impacted versus the associated in river sonde conductivity plume impact time (e.g., 

Appendix B.5), it was observed that the automated sampler did not capture the main discharge 

plume which was still clearly evident and not fully mixed. The systematic mismatch of Isco 

sampling and CWTF discharge plume impact times encountered at site S03-Downstream1 during 

the high discharge sampling campaign biased the relative impact down in relation to both the 

impact observed at the site during the low river discharge campaigns and the S04-Downstream2 

and S05-PDW1 sites during the high river discharge campaign. While Cl- presented a similar 

overall response as Br- (Figure 4b) demonstrating a clear impact from CWTF effluent, the S05-

PDW1 site high river discharge sampling period Cl- concentration was significantly higher 

(p=0.016) than S01-Upsteam during non-discharge days (Table 2); suggesting another 
contributing source(s) (e.g., CFPP discharge) and precluding its inclusion in the inter-site 

analysis.

The impact of CWTF effluent discharge on downstream sites within the study domain was also 

evaluated using CWTF discharge categorized intra-site analysis, whereby the CWTF impacted 

and non-impacted sample subsets at each site were statistically compared (Table 4; Figures 4a-c). 

Both downstream river sites (S03-Downstream1, S04-Downstream2) and S05-PDW1 were found 

to have significantly higher conductivity, Br-, and Cl- during both high and low river discharge 

conditions when being impacted by the CWTF effluent discharge plume. The discharge 

categorized data from the high and low discharge regime campaigns used for intra-site analysis 

are presented in Table 4 and are depicted in Figures 4a-c. The S01-Upstream conductivity data 

174 ± 13 μS cm-1 has a relatively tight range compared to the CWTF downstream sites and the 

distribution is not significantly different than normal (Shapiro-Wilk; p=0.166; Figure 4c). The 

magnitude of the mean conductivity impact from the CWTF on downstream sites during low

river discharge, determined by evaluating all the impacted versus non-impacted categorized 

samples, was an increase of 15% (28 μS cm-1) at S03-Downstream1, 12% (23 μS cm-1) at S04-

Downstream2, and 12% (23 μS cm-1) at S05-PDW1. The CWTF discharge categorized Cl- data 

from the low discharge regime campaigns are depicted in Figure 4b. Using the same analytical 

approach described above, the magnitude of the Cl- impact from the CWTF discharge on 

downstream sites was an increase of 40% (8.4 ppm) at S03-Downstream1, 21% (4.5 ppm) at 

S04-Downstream2, and 19% (4.3 ppm) at S05-PDW1. The CWTF discharge categorized Brdata from the low discharge regime campaigns are depicted in Figure 4a. The magnitude of the 

Br- impact during the low discharge regime was an increase of 105% (79 ppb) at S03-

Downstream1, 55% (39 ppb) at S04-Downstream2, and 53% (39 ppb) at S05-PDW1. In 

contrast, the S01-Upstream baseline and non-impacted downstream Br- mean concentrations 

were indistinguishable (74 ± 2 ppb), which is a strong indication that non-impacted samples were 

properly categorized and that there were no other significant sources of Br- in the study domain

(Figure 4a).
During the high river discharge sampling regime the overall observed concentrations and the 

magnitude of CWTF impact were lower at all downstream sites due to the river’s increased 

dilution capacity. The CWTF effluent discharge enhancement for (i) conductivity was an 

increase of 7% (9 μS cm-1) at S03-Downstream1, 6% (8 μS cm-1) at S04-Downstream2, and 2% 

(3 μS cm-1) at S05-PDW1, (ii) Cl- was an increase of 20% (2.7 ppm) at S03-Downstream1, 11% 

(1.5 ppm) at S04-Downstream2, and 5% (0.9 ppm) at S05-PDW1, and (iii) Br- was an increase of 

75% (18 ppb) at S03-Downstream1, 31% (8 ppb) at S04-Downstream2, and 22% (7 ppb) at S05-

PDW1.

Cl-

/Br- Ratio

Halide ratios (e.g., Cl-/Br-) are used in hydrogeological studies to elucidate water migration 

because the species primarily occur as dissolved monovalent ions that typically are conserved 

during movement through environmental compartments (Davis et al., 1998; Freeman 2007; 

Alcala and Custodio, 2008). Formation water from Devonian oil- and gas-bearing units such as 

the Marcellus are enriched in Br- resulting in characteristically lower Cl-/Br- ratios (Ferrar et al.,

2013; Warner et al., 2013). The Cl-

/Br- ratio of the S02-CWTF discharge was significantly 

different (Kruskal-Wallis p<0.0001) during the high (n=13; 110.6 ± 6.2) and low (n=23; 90.4 ± 

2.4) discharge regime sampling campaigns. The Cl-/Br- ratio of data presented by Warner et al., 

(2013; and references within) was 127.2 from a similar CWTF discharge in Western 

Pennsylvania treating a combination of Marcellus and conventional Devonian produced 

wastewater (2010-2012), 107.8 from raw upper Devonian produced water, 93.4 from raw 

Marcellus produced water, and 108.5 from raw Lower Devonian produced water. The discharge 

categorized Cl-

/Br- ratio data from the low discharge regime campaigns indicate higher values 

were observed during non-impact conditions compared to impacted conditions (Figure 5). 

Similar to the Br- results, good agreement between the low discharge regime S01-Upstream 

(316.0 ± 80.3) and non-impact categorized downstream Cl-/Br- ratios is an indication of no 

additional significant sources of Br- enriched discharge into the study domain. A significant 

reduction (p=0.023) of the Cl-/Br- ratio is observed at the S03-Downstream1 site when being 

impacted by the CWTF discharge (205.9 ± 38.9) and then increases as the halides are diluted by 

the more Cl- dominated baseline river flow (316.0 ± 80.3) down to sites S04-Downstream2 
(246.2 ± 33.6) and S05-PDW1 (243.7 ± 35.5; Figure 5). Within the upper Allegheny study 

domain (S01-Upstream to S05-PDW1) elevated total Br- and low Cl-/Br- sample ratios appear to 

be a good indicator of CWTF discharge downstream impact.

In the context of S06-PDW2 and other locations in the lower reaches of Allegheny River 

watershed, interpretation of Cl-

/Br- ratios becomes more difficult as the number of sources 

discharging into the river and its tributaries dramatically increase (e.g., public/commercial 

wastewater treatment facilities, discharges from coal mines, coal bed methane (CBM), CFPP). 

The mean Cl-

/Br- ratio observed at S06-PDW2 during the high river discharge regime (460 ± 71) 

was significantly higher (p<0.0001) than the Cl-

/Br- ratio during the low river discharge regime 

(216 ± 17), suggesting that the elevated halides measured during the low river discharge 

campaign were the result of discharges of wastewaters containing characteristically lower Cl-/Brratios into the river. Coal mined in the region from the upper Pennsylvanian Conemaugh and 

Monongahela formation bituminous coals (e.g., Pittsburgh #8; Kosanke, 1984) have been found 

to contain high concentrations of Br- (13.4 ppm) and a low Cl-/Br- ratio of 72.6 (Seere and Lee, 

2009). In addition, contemporaneously collected samples of wastewater discharges from other 

anthropogenic activities exploiting the same coal formations and discharging into the Allegheny 

River or its tributaries between sites S05-PDW1 and S06-PDW2 also contain Cl-

/Br- ratios 

substantially lower that the upper Allegheny baseline S01-Upstream values (316.0 ± 80.3)

including: coal ash (40.7), treated FGD (68.4), CBM (129.9), treated AMD (158.1), AMD seeps

(172.6), and active coal mine runoff (183.0; EPA 2015).

The timeline of increasing PDW THM concentrations along the Allegheny River and its 

perceived correlation to expanding exploitation of the Marcellus shale in western Pennsylvania 

for gas and oil production reported by States et al. (2013), was also concurrent with the regional 

trend of installing air pollution control systems in CFPPs. The development of the EPA 2005 

Clean Air Interstate Rule, the 2011 Cross-State Air Pollution Rule, and the 2011 Mercury and 

Air Toxics Standards have led to the wide spread retrofitting of the US CFPP fleet with FGD 

scrubbers. Scrubber installations reached 64% of CFPPs by the end of 2012 (US Energy 

Information Administration). Among other pollutants such as SO2 and divalent mercury species 
(e.g., HgCl2, HgBr2), scrubbers also efficiently remove halides from the stack gas that originates 

naturally in the combusted coal. Once FGD scrubbers remove components from the stack 

exhaust (e.g., halides and sulfur dioxide), CFPPs typically discharge treated scrubber wastewater 

as well as storm water runoff from coal and residual ash piles enriched in halides and sulfate to 

surface waters in western Pennsylvania (U.S. EPA 2015).

Upper Allegheny Mass Balance Model

The water volume closure of the box model in the upper Allegheny study domain was evaluated 

using the results calculated using Equation 1, and the daily mean volume closure was found to be 

88 ± 11%. The model on average underestimated the volume of water in the system because of 

inflows from three ungaged tributaries (Turkey Run, Sandy Creek, Scrubgrass Creek) into the 

Allegheny River between sites S01-Upstream and S05-PDW1 (Appendix B.2) were not included 

in the model. Water volume closure during the high river discharge regime (95 ± 12) was on 

average better than during the low river discharge regime (84 ± 8).

During the low discharge campaigns, the river baseline flow contributed an average of 448 kg of 

Br- and 133,970 kg of Cl- into the model domain on CWTF discharge days. The daily mean 

source contribution from S02-CWTF was 202 kg Br- and 18,208 kg Cl-

, the contribution from 

the POTW was 0.0 k g Br- and 1,332 Cl-

, and the contribution from the CFPP was 0.1 kg Br-; and 

196 kg Cl-

. Assuming homogeneous steady state conditions with no additional source terms, the 

box model predicts the S02-CWTF discharge would contribute an average of 44 ± 22% of the Brand 14 ± 7% of the Cl- into the upper Allegheny River sampling domain (Figure 6a). The box 

model results agree well with the 53% Br- (39 ppb) and 19% Cl- (4.3 ppm) contributions from 

the intra-site analysis, and the 51% Br- (38 ppb) and 26% Cl- (5.4 ppm) contributions from the 

inter-site analysis at S05-PDW1 (Table 5). The daily box model average estimated total Brmass (649 kg day-1

) contribution into the upper Allegheny River domain was within 8% of the 

S05-PDW1 measurement based Br- mass estimate (703 kg day-1), indicating the observed impact 

at PDW1 during low river discharge could be explained through the contributions of the three 

known discharge sources into the river within the uncertainty of the water volume closure.

During the high river discharge measurement campaign, the Allegheny River water volume was 

five times greater than during the low river discharge measurement campaigns. While the high 
discharge campaign halide concentrations were lower, the river baseline discharge contributed 

more than double the halide mass (mean of 973 kg of Br- and 490,853 kg of Cl-) into the model 

domain per CWTF discharge day than was observed during the low river discharge periods. The 

daily mean source contributions from S02-CWTF was 159 kg Br- and 17,323 kg Cl- (Figure 6b). 

The daily mean source contributions from the POTW and CFPP were 0.0 and 0.1 kg Br-

; and 

1,534 and 147 kg Cl-

, respectively. During the high discharge regime the box model predicts the 

S02-CWTF discharge would contribute 16 ± 6% of the Br- and 4 ± 1% of the Cl- into the river 

domain. While the box model results agree relatively well with the 22% Br- (7 ppb) and 5% Cl-

(0.9 ppm) contributions from the intra-site analysis (Table 5), overall it under predicts the total 

average daily loading in the river versus the S05-PDW1 measurement based estimates (Figure 

6b). The generally higher CWTF impact estimated by the inter- and intra-site analyses was 

expected as the Isco sampling times were coincident with the CWTF effluent conductivity

impacts measured at S05-PDW1 by the in-river sonde, whereas the box model assumes a 

homogeneous well mixed system. The observed CWTF effluent discharge impacts at S05-

PDW1 suggests the impacts of the elevated halide concentrations on the raw water plant intake 

could be partially mitigated by conditional pumping based on near-field upstream conductivity

measurements.

Implications of CWTF Discharges on PDW THM Concentrations

As reported by States et al. (2013) the PWSA and other water utility operators relying on the 

Allegheny as their raw water source observed significantly increased total THM concentrations 

and substantially higher than normal relative abundances in brominated analogs in 2010, and

hypothesized that these observations were a result of increased Br- concentrations in their river 

source water. A time series analysis of Allegheny River Br- concentration was not possible then

as routine Br- measurements by PADEP were not initiated until late 2009 (USEPA, 2014). A 

current time series of quarterly THM concentrations in finished drinking water and the annual 

rolling averages are presented in Figure 7a for site S05-PDW1 using all available data contained 

in the PADEP Drinking Water Reporting System (PADEP, 2014). An upward trend in the 

annual rolling average of THMs in finished drinking water, and an underlying seasonal variation 

are observed. A linear regression analysis was completed for quarterly THM rolling 

concentrations from 2010-Q1 through 2014-Q4 (Figure 7b) and a significant (p<0.0001; 
r

2

=0.864) increasing trend of ~6 ppb per year was found. At this rate, S05-PDW1 will exceed 

the EPA THM standard of 80 ppb by 2016. The Q3 THM concentrations for 2010 through 2014 

are significantly higher than the other quarters (p=0.011) reported during this period. The likely 

contributing factors to elevated Q3 THM concentrations are significantly higher Br- (p=0.015)

and organic carbon (p<0.0001) concentrations during the low river discharge regimes, as well as 

the higher water temperatures in the summer (Appendix A.2).

EPA’s empirical raw water DBP treatment model was used to estimate the impact of the CWTF 

discharge on S05-PDW1 THM formation by comparing discharge impacted and non-discharge 

impacted intra-site analysis scenarios during the low (2012-Q3) discharge regime when the 

highest THM concentrations are reported (Figure 7a). The mean low river discharge non-impact 

categorized Br- concentration from S05-PDW1 (73 ppb; Table 4) and CWTF impacted

categorized (112 ppb; Table 4) samples were used to parameterize successive model runs. The 

predicted total THM concentration for the non-impacted baseline river condition was 105 ppb, 

and the predicted CWTF discharge impacted river condition yielded an estimated total THM 

value of 109 ppb (3% increase). While the additional Br- in the S05-PDW1 raw water intake 

attributed to the CWTF enhancement discharge was not estimated to substantially contribute to

the overall total THM, the model predicted an overall decrease in chlorinated THM analogs and 

a large 41% increase in the more toxic brominated THM analogs. The model estimated a 37% 

increase in bromodichloromethane (19.0 to 26.0 μg L-1), a 113% increase in bromoform (0.2 to 

0.4 μg L-1

), and a 117% increase in dibromochloromethane (4.0 to 8.7 μg L-1). 

Since S06-PDW2 samples could not be categorized as impacted and non-impacted by S02-

CWTF due to the dissipation of the conductivity plume and additional downstream sources, the 

relative impact of aggregate CWTF discharges were based on the receptor modeling results from 

measurements made during this same study period at S06-PDW2 (U.S. EPA 2015). During the 

low river discharge regime, U.S. EPA (2015) attributed 37% and 59% of Br- at S06-PDW2 to 

CWTF discharges and coal-fired power plants equipped with flue gas desulfurization scrubbers, 

respectively. EPA’s empirical raw water DBP treatment model was used to estimate the impact 

of the total aggregate of CWTF discharges on S06-PDW2 THM formation by comparing mean 

observed Br- concentration to the mean Br- concentrations minus the estimated aggregate CWTF 
contributions during the low (2012-Q3) discharge regime. The mean low river discharge Brconcentration from S06-PDW2 (142 ppb; Table 1) and the Br- concentration with the estimated 

37% CWTF contribution removed (89 ppb) were used to parameterize successive model runs. A

predicted total THM contribution at S06-PDW2 from CWTF attributed Br- was 3 ppb, with a 

47% increase in brominated THM analogs. The model estimated a 41% increase in 

bromodichloromethane (18.2 to 25.7 μg L-1), a 128% increase in bromoform (0.3 to 0.7 μg L-1), 

and a 133% increase in dibromochloromethane (5.0 to 11.5 μg L-1

).

The empirical THM modeling results corroborate the States et al. (2013) conclusion that 

increased Br- concentrations in the Allegheny River attributable to CWTF wastewater discharges 

water can substantially shift PDW total THM from chlorinated to more toxic brominated 

analogs. However, the empirical THM modeling does not support the contention that Brattributed to CWTF discharges affects the overall trend of increasing THM concentrations 

(Figure 7b). From 2010 to 2014, PADEP data shows a significantly (p=0.0045) decreasing Brtrend in the upper reaches of the Allegheny River in the vicinity of S05-PDW1 (Figure 7c) 

during the concurrent increasing trend in total THM (Figure 7b). The significantly decreasing 

Br- trend (p=0.005; Appendix B.7) is also observed in the lower reaches of the Allegheny River 

in the vicinity of S06-PDW2 during the concurrent (p=0.003) increasing trend in total THM from 

2010 to 2013 (Appendix B.6). A sensitivity analysis of the THM formation model parameterized 

for both S05-PDW1 and S06-PDW2 suggests the increasing trend is more likely due to 

variability in the Allegheny River dissolved organic carbon (DOC) concentrations. 

Unfortunately, the available Allegheny River data includes primarily total organic carbon (TOC)

rather than DOC concentrations which are more relevant to THM formation (U.S. EPA, 1998; 

Solarik et al., 2000). There are no significant trends observed in the TOC data in either the upper 

(p=0.18; Figure 7c) or lower (p=0.15; Appendix B.7) Allegheny River.

Conclusions

As a result of Marcellus formation wastewater being diverted to other reuse and disposal options 

(PADEP, 2014), there has been a drastic reduction in the volume of oil and gas wastewater 

being discharged into the upper Allegheny River and a corresponding decreasing trend in 
observed Br- surface water concentrations 2009-2014 (Figure 7c; Figure Appendix B.7). But 

despite the declining Allegheny River Br- concentration, a significant impact of ongoing CWTFs 

operations to observed Br- concentrations during the high (2012 Q2) and low (2012 Q3) river 

discharge sampling campaigns were observed at downstream PDW intakes in both the upper and 

lower reaches of the river. On days with active CWTF effluent discharge the magnitude of Brenhancement at S05-PDW1 increased by an average of 39 ppb (53%) and 7 ppb (22%) for high 

and low river discharge campaigns, respectively. The CWTF attributed Br- resulted in small 

modeled increase in total THM (3%), but a substantial positive shift from chlorinated to more 

toxic brominated THM analogs at both S05-PDW1 (41%) and S06-PDW2 (47%).

Suggestions for Future Monitoring

While various sources of surface water and PDW analytical results are available in the public 

domain (EPA STORET, PADEP DWPS), the fragmented nature both spatially and temporally 

between open river and PDW sample collection as well as the lack of DOC data prevent a 

process level understanding behind the underlying mechanisms for THM formation and the 

causality of observed trends. Integrating and coordinating the PDW and surface water 

Fimonitoring programs (e.g., sampling locations, time, analytes, parameters) would provide a 

basis for evaluating/modeling THM production mechanisms and underlying system dynamics.

Acknowledgements: The EPA through its Office of Research and Development funded and 

conducted this research. The views expressed in this paper are those of the authors and do not 

necessarily reflect the views or policies of EPA. It has been subjected to Agency review and 

approved for publication. Mention of trade names or commercial products do not constitute an 

endorsement or recommendation for use. We thank Ram Vedantham, Sania Tong-Argao, and 

Clay Nelson (EPA ORD) for their assistance with data Quality Assurance; Todd Krantz and 

Chris Impellitteri (EPA ORD), Angela McFadden, Louis Reynolds, Kelly Krock (EPA Region 

3), Sam Garvey and Mike Wheeler (Alion) for their logistical assistance; and the CWTF and 

PDW operators for voluntary access to their facilities.
1 List of Figures

2 Figure 1. Plot of Allegheny River sampling domain depicting the locations of sampling sites and 

3 major source discharges. River distances downstream from S02-CWTF discharge are 

4 noted in parentheses.

5 Figure 2. Plot depicting concurrent Onset in-river sonde high resolution (5 min) specific 

6 conductivity observations demonstrating CWTF discharge plume transit time from site 

7 S02-CWTF (sonde located 45 m downstream from discharge pipe; CWTF-P45) to site

8 S03-Downstream1 (black trace). Drop lines denote the median discharge time (S02-

9 CWTF) and conductivity peak from each plume impact event (S03-Downstream1), 

10 respectively. The difference between the drop lines represents the plume transit time.

11 Figure 3. Plot depicting transit time corrected Onset in-river sonde high resolution (5 min) 

12 specific conductivity observations at S03-Downstream1 during low discharge regime 

13 demonstrating how Isco samples were categorized as CWTF “discharge impacted” 

14 (Monday-Friday) and “non-impacted” (Saturday). Drop down lines denote Isco 

15 sampling times.

16 Figure 4. Comparison of Allegheny River low discharge regime S01-Upstream site paired 

17 sample baseline subtracted (a) bromide, (b) chloride, (c) specific conductivity, and (d) 

18 sulfate by site location and CWTF discharge impacted versus non-impacted time 

19 periods. Dashed line indicates relative river “baseline” value.

Figure 5. Comparison of Allegheny River low discharge regime Cl-/Br- 20 ratio by site location and 

21 CWTF discharge impacted versus non-impacted time periods. Dashed line indicates 

22 median “baseline” value at S01-Upstream site.

23 Figure 6. Box model results for high (a) and low (b) flow regimes in the upper Allegheny River 

24 study domain (Baseline includes mass from S01-Upstream, POTW, and CFPP).

25 Figure 7. Time series plots of S05-PDW1 quarterly mean (a) 2004 – 2014 rolling annual mean 

26 THM concentration in finished drinking water in relation to the 80 ppb EPA standard, 

27 (b) 2010 – 2014 significantly increasing THM concentration in finished drinking water 

trend of ~ 6 ppb year-1 28 , (c) 2010 – 2014 trends of bromide and total organic carbon

29 (trend is not significant at α = 0.05). The box delineates the two quarters during the 

30 2012 EPA field sampling campaigns.

31
32 Figure 1.

33

Indiana 

• 

Legend 

• Publicly Owned Sewage Treatment Works 

.A. Commercial Waste Treatment Facility 

• Coal Fired Power Plant 

0 River Sampling Site 

® Public Dtinking Water Intake 

--interstate 

Highways 

.. Allegheny River 

.. Ttibutaties 

Urban Area 

LJ County Line 

S04-Downstream2 ( 43.5 km) 

0 1.5 3 6 

- -
34 Figure 2.

35

36
37 Figure 3.

38

39

1600 260 

1400 

240 .,.... -I 

E 

- 1200 (..) .,.... I 

(/) E 

(..) :l. 

(/) 1000 

- 220 () :l. (/) -() T""" 

(/) 800 E 

l() ro 

Q) ~ L... 

a... 200 

-

C/) I 600 c LL 

I- 3: 

s 0 

0 

() 400 I 

("") 

180 0 

(/) 

200 

0 160 

..... ~ R) ..... ~ ..... ~ ..... ~ ..... ~ ..... ~ ..... ~ R) R) R) R) R) R) 

~rp B-rp ~rp ;'\\t ~rp ~rp ~rp cy'V cyrp cy~ cyf); cy'V cyrp cyOj 
40 Figure 4. 

41

200 (a) Non-Impacted Impacted Non-Impacted Impacted Non-Impacted Impacted 

150 

7l 

a. 

.!:!: 

Q) 

100 1 1 1 1 1 "C 

E 

e 

CXl 

<] : -- ---- ~- -- ---- -- ~ --------- . . ~ -50 

20 (b) 

15 

• 

5 • 

0 ---$----~~- --~--------

-5 

80 (c) 

60 

• 

40 

20 

0 --- ------- • 

-20 

5 (d) 

4 

'E 3 a. 

.!:!: 

Q) 

l§ 

"3 

(/) 

<] 

2 

0 ___ $ _, _______ _ 

S03 - Downstream 1 

-12 km 

---- --------

• Q 

• 

S04 - Downstream 2 

- 44 km 

• 

• 

B 

S05 - POW 1 

-52 km 

-· 
42 Figure 5.

43

S01 - Upstream S03 - Downstream 1

~12 km

S04 - Downstream 2

~44 km

S05 - PDW 1

~52 km

Non-impacted Impacted

Chloride/Bromide Ratio

100

200

300

400

500

Non-impacted Impacted Non-impacted Impacted

S06 - PDW 2

~150 km

44
45 Figure 6. 

46

(a) Low River Discharge Regime 

SOl-Upstream + POTW + CFPP 

448 kg Br dayl 

135,498 kg Cl dayl 

S02-CWTF 

202 kg Br dayl 

18,208 kg Cl dayl 

(b) High River Discharge Regime 

SOl-Upstream + POTW + CFPP 

973 kg Br dayl 

492,534 kg Cl dayl 

S02-CWTF 

159 kg Br dayl 

17,323 kg Cl dayl 

SOS-PDWl (Actual) 

703 kg Br dayl 

167,034 kg Cl dayl 

SOS-PDWl (Actual) 

1475 kg Br dayl 

671,763 kg Cl dayl 
47 Figure 7a.

48

2004_Q12004_Q22004_Q32004_Q42005_Q12005_Q22005_Q32005_Q42006_Q12006_Q22006_Q32006_Q42007_Q12007_Q22007_Q32007_Q42008_Q12008_Q22008_Q32008_Q42009_Q12009_Q22009_Q32009_Q42010_Q12010_Q22010_Q32010_Q42011_Q1

2011_Q22011_Q32011_Q42012_Q12012_Q22012_Q32012_Q42013_Q12013_Q22013_Q32013_Q42014_Q12014_Q22014_Q32014_Q4

Total Trihalomethane (ppm)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

Quarterly Average

80ppb Starndard

Rolling Average

(a)

49

50
51 Figure 7b.

2010_Q12010_Q22010_Q32010_Q42011_Q12011_Q22011_Q32011_Q42012_Q12012_Q22012_Q32012_Q42013_Q12013_Q22013_Q32013_Q42014_Q12014_Q22014_Q32014_Q4

Total Trihalomethane (ppm)

0.04

0.05

0.06

0.07

0.08

THM = 0.0016 * (Quarter) + 0.0490

 r

2 = 0.864

p < 0.0001

(b)

52
53 Figure 

7c.

2009Q42010Q12010Q22010Q32010Q42011Q12011Q2

2011Q32011Q42012Q12012Q22012Q32012Q42013Q12013Q22013Q32013Q42014Q12014Q22014Q32014Q4

Bromide (ppb)

0

50

100

150

200

250

300

TOC (ppm)

0.0

1.0

2.0

3.0

4.0

Bromide 

TOC

(c)

Br- = -7.727 * (Quarter) + 165.3

r2 = 0.474

p = 0.0045

54
55 Table 1. Summary of Allegheny River High (April 30 - May 14, 2012) and Low (July 5-19 & September 19-October 4, 2012) 

56 Discharge Isco Sample Results (Kruskal Wallis Tests Indicate all Low Discharge Concentrations are Higher at all Sampling 

57 Sites p < 0.0001).

58

59

60

S01-Upstream S03-Downstream1 S04-Downstream2 S05-PDW1 S06- PDW2

High Low High Low High Low High Low High Low

Spec. Cond.

(μS cm-1

)

n 15 31 14 31 13 30 15 26 15 28

Median 126 174 131 187 142 198 158 202 186 360

Mean 126 174 132 193 142 200 157 204 182 374

Range 116-143 150-194 112-154 154-262 127-157 168-243 144-171 177-250 152-215 271-608

Bromide

(ppb)

n 15 31 13 30 13 30 12 26 15 28

Median 25 72 28 88 32 78 38 85 35 132

Mean 26 72 34 101 31 85 36 87 35 142

Range 22-36 33-117 19-56 37-277 20-36 38-154 27-41 39-166 26-44 103-202

Chloride

(ppm)

n 15 31 14 31 13 30 15 26 15 28

Median 13.1 21.0 13.8 22.5 14.0 22.5 17.0 23.5 15.9 29.6

Mean 13.5 20.8 14.7 23.8 14.3 23.3 17.3 23.6 15.9 30.4

Range 12.4-16.2 16.2-25.8 12.3-19.2 16.6-41.3 12.8-16.6 17.3-31.3 15.6-18.7 17.6-32 13.1-21.9 24.5-37.3

Sulfate

(ppm)

n 15 31 14 31 13 30 15 26 15 28

Median 10.3 7.5 11.9 8.3 11.6 8.9 11.1 9.5 27.0 83.2

Mean 10.7 7.5 11.3 8.4 11.5 9.0 11.3 9.6 28.7 82.0

Range 9.7-13.5 6.8-8.6 3.7-12.8 7.8-9.7 10.2-12.8 8-11.7 10.3-13.1 8.5-10.8 23.3-39.9 47.6-128.8
61 Table 2. Summary of Spring (April 30 - May 14, 2012) CWTF Discharge Categorized Paired Isco Sample Results for Inter-site 

62 Analysis, and Kruskal Wallis Non-parametric Hypothesis Test Results (bold are significant).

63

No Discharge Discharge No Discharge Discharge No Discharge Discharge

S01-

Upstream

S03-

Downstream1

S01-

Upstream

S03-

Downstream1

S01-

Upstream

S04-

Downstream2

S01-

Upstream

S04-

Downstream2

S01-

Upstream

S05- 

PDW1

S01-

Upstream

S05- 

PDW1

Spec.

Cond.

(μS cm-1

)

Paired n 7 7 6 7 7 7

Median 127 130 123 132 125 137 127 148 123 158 127 161

Mean 124 128 128 137 126 137 127 145 125 156 127 159

Range 116-131 112-137 116-143 122-154 118-138 127-151 116-143 130-157 118-138 144-166 116-143 148-171

p-Value 0.109 0.016 0.031 0.016 0.016 0.016

Bromide 

(ppb)

Paired n 6 7 6 7 4 7

Median 24 24 26 41 25 27 25 34 27 34 25 39

Mean 25 24 28 42 27 26 26 34 28 34 26 39

Range 22-30 19-28 24-36 26-56 22-36 20-32 23-32 32-36 23-36 28-39 23-32 36-41

p-Value 0.281 0.016 0.844 0.016 0.250 0.016

Chloride 

(ppm)

Paired n 7 7 6 7 7 7

Median 13.3 13.3 13 15.0 13.1 13.1 13.6 15.1 13 16.4 13.6 18

Mean 13.1 13.3 13.9 16.0 13.5 13.5 13.7 15.0 13.4 16.8 13.7 17.7

Range 12.6-13.6 12.3-13.9 12.4-16.2 13.6-19.2 12.4-16.2 12.8-15.8 12.6-16 13.2-16.6 12.4-16.2 15.6-18.4 12.6-16 16.8-18.7

p-Value 0.469 0.016 1.000 0.016 0.016 0.016

Sulfate 

(ppm)

Paired n 7 7 6 7 7 7

Median 10.1 11.9 10.3 11.9 10.9 11.5 9.9 11.6 10.6 11.1 9.9 11

Mean 10.5 10.7 10.4 11.9 11 11.7 10.5 11.4 10.9 11.3 10.5 11.3

Range 9.8-12.3 3.7-12.8 9.7-12.3 11.1-12.4 9.8-12.3 11.1-12.8 9.8-13.5 10.2-12 9.8-12.3 10.5-13.1 9.8-13.5 10.3-12.7

p-Value 0.375 0.031 0.313 0.156 0.813 0.109
64 Table 3. Summary of Summer and Fall (July 5-19 & September 19-October 4, 2012) CWTF Discharge Categorized Paired Isco 

65 Sample Results for Inter-site Analysis, and Kruskal Wallis Non-parametric Hypothesis Test Results (bold are significant).

66

No Discharge Discharge No Discharge Discharge No Discharge Discharge

S01-

Upstream

S03-

Downstream1

S01-

Upstream

S03-

Downstream1

S01-

Upstream

S04-

Downstream2

S01-

Upstream

S04-

Downstream2

S01-

Upstream

S05- 

PDW1

S01-

Upstream

S05- 

PDW1

Spec. 

Cond. 

(μS cm-1

)

Paired n 20 9 17 9 15 9

Median 174 182 173 199 174 193 173 212 174 202 173 208

Mean 174 185 175 211 175 195 175 213 174 199 175 219

Range 151-194 164-229 150-194 178-262 161-194 181-216 150-194 188-243 161-194 181-222 150-194 197-250

p-Value <.001 0.004 <.001 0.004 <.001 0.004

Bromide 

(ppb)

Paired n 19 9 17 9 15 9

Median 78 74 71 134 77 71 71 102 80 71 71 107

Mean 75 77 74 155 75 74 74 107 80 77 74 112

Range 37-117 46-112 33-112 84-277 37-117 45-112 33-112 75-154 37-117 43-117 33-112 77-166

p-Value 0.731 0.004 0.927 0.004 0.454 0.004

Chloride 

(ppm)

Paired n 20 9 17 9 15 9

Median 21.3 21.3 21 27.1 21.3 21.9 21 24.7 21.9 22.2 21 25

Mean 21.1 21.4 21 29.5 21.2 22 21 25.6 21.6 22.6 21 26.4

Range 16.3-25.8 17.9-24.9 16.2-25.3 22.4-41.3 16.3-25.8 18.7-25.6 16.2-25.3 22-31.1 16.3-25.8 18.6-26.5 16.2-25.3 22.4-32

p-Value 0.729 0.004 0.089 0.004 0.107 0.004

Sulfate 

(ppm)

Paired n 20 9 17 9 15 9

Median 7.6 8.2 7.4 8.3 7.6 8.8 7.4 9.1 7.6 9.5 7.4 9.7

Mean 7.6 8.3 7.3 8.6 7.6 8.9 7.3 9.3 7.6 9.7 7.3 9.6

Range 7.0-8.6 7.8-8.8 6.8-7.6 7.9-9.7 7.0-8.6 8-10.8 6.8-7.6 8.6-11.7 7.0-8.6 8.5-10.8 6.8-7.6 9.0-10.0

p-Value <.001 0.004 <.001 0.004 <.001 0.004

67

68

69
70 Table 4. Summary of all Isco Sample Analysis at Downstream Sites S03-Downstream1 to S05-PDW1 Categorized as either CWTF 

71 Discharge or Non-Discharge Impacted, and Intra-site CWTF Impact Analysis Results for those Species found to be 

72 Significantly Higher. 73

74

High River Discharge Low River Discharge

Species Site Non-discharge Discharge

One-Sided 

t Appx

CWTF 

Contribution Non-discharge Discharge

One-Sided 

t Appx

CWTF 

Contribution

S03-Downstream1

Total n 7 7

0.19

21 10

<0.01

Mean ± SD 128 ± 8 137 ± 12 184 ± 16 212 ± 28 28 (15%)

Spec. Cond. S04-Downstream2

Total n 6 7

0.12

19 11

<0.01

(μS cm-1) Mean ± SD 137 ± 9 145 ± 10 192 ± 12 215 ± 20 23 (12%)

S05-PDW1

Total n 8 7

0.17

17 9

0.01

Mean ± SD 156 ± 7 159 ± 9 196 ± 13 219 ± 23 23 (12%)

S03-Downstream1

Total n 6 7

0.01

20 10

<0.01

Mean ± SD 24 ± 4 42 ± 11 18 (75%) 75 ± 20 154 ± 64 79 (105%)

Bromide S04-Downstream2

Total n 6 7

<0.01

19 11

<0.01

(ppb) Mean ± SD 26 ± 6 34 ± 1 8 (31%) 71 ± 20 110 ± 30 39 (55%)

S05-PDW1

Total n 5 7

0.05

17 9

<0.01

Mean ± SD 32 ± 5 39 ± 2 7 (22%) 73 ± 23 112 ± 32 39 (53%)

S03-Downstream1

Total n 7 7

0.02

21 10

<0.01

Mean ± SD 13.3 ± 0.6 16.0 ± 2.4 2.7 (20%) 21.1 ± 2.4 29.5 ± 6.1 8.4 (40%)

Chloride S04-Downstream2

Total n 6 7

0.03

19 11

<0.01

(ppm) Mean ± SD 13.5 ± 1.2 15.0 ± 1.2 1.5 (11%) 21.6 ± 2.3 26.1 ± 3.4 4.5 (21%)

S05-PDW1

Total n 8 7

0.04

17 9

<0.01

Mean ± SD 16.8 ± 1.0 17.7 ± 0.7 0.9 (5%) 22.1 ± 2.6 26.4 ± 3.5 4.3 (19%)

S03-Downstream1

Total n 7 7

0.48

21 10

0.15

Mean ± SD 10.7 ± 3.2 11.9 ± 0.5 8.3 ± 0.4 8.6 ± 0.6

Sulfate S04-Downstream2

Total n 6 7

0.36

19 11

0.11

(ppm) Mean ± SD 11.7 ± 0.6 11.4 ± 0.6 8.9 ± 0.6 9.2 ± 0.9

S05-PDW1

Total n 8 7

0.33

17 9

0.39

Mean ± SD 11.3 ± 0.9 11.3 ± 1.0 9.7 ± 0.7 9.6 ± 0.4
75

76 Table 5. Summary of all CWTF Impact Analysis Results at Downstream Sampling Sites S03-Downstream1 to S05-PDW1 on 

77 Effluent Discharge Days.

78

79

High River Discharge Low River Discharge

Species Site Inter-site Intra-site Box Model Inter-site Intra-site Box Model

Spec. Cond.

(μS cm-1

)

S03-Downstream1 . . . . 28 (15%) .

S04-Downstream2 . . . . 23 (12%) .

S05-PDW1 . . . . 23 (12%) .

Bromide

(ppb)

S03-Downstream1 14 (50%) 18 (75%) . 81 79 (105%) .

S04-Downstream2 8 (31%) 8 (31%) . 33 (45%) 39 (55%) .

S05-PDW1 13 (50%) 7 (22%) 4 (16%) 38 (51%) 39 (53%) 30 (44%)

Chloride

(ppm)

S03-Downstream1 2.1 (15%) 2.7 (20%) . 8.5 (40%) 8.4 (40%) .

S04-Downstream2 1.3 (9%) 1.5 (11%) . 4.6 (22%) 4.5 (21%) .

S05-PDW1 . 0.9 (5%) 0.5 (4%) 5.4 (26%) 4.3 (19%) 2.8 (14%)

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