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Anumol et al. | http://dx.doi.org/10.5942/jawwa.2015.107.0129
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Point-of-Use Devices for Attenuation of Trace Organic
Compounds in Water
TARUN ANUMOL,1, 2 BRADLEY O. CLARKE,1, 3 SYLVAIN MEREL,1, 4
AND SHANE A. SNYDER1, 5
1Department
of Chemical and Environmental Engineering, University of Arizona, Tucson
Technologies, Wilmington, Del.
3RMIT University, School of Applied Sciences, Melbourne, Australia
4Department of Geosciences, University of Tübingen, Tübingen, Germany
5National University of Singapore Environmental Research Institute, Singapore
2Agilent
Trace organic compounds (TOrCs) continue to be detected in
drinking water, and their recalcitrance makes them difficult to
attenuate without installing expensive advanced treatment
processes. Because human consumption is a small portion of net
household water use, point-of-use (POU) devices may provide
additional security against drinking water contaminants. This
research evaluated three pitcher and two refrigerator POU devices
using two waters. Refrigerator POU devices removed more
TOrCs over the manufacturer’s expected lifetime in terms of total
mass than the pitcher POU devices. Average removal through all
filters for nonionic, hydrophobic compounds was higher than for
hydrophilic compounds in both waters. Removal of ionic
compounds was enhanced by cation/anion exchange resins
present in pitcher POU devices. Results indicated that POU
devices are capable of removing significant amounts of organic
contaminants in water. However, removal of a specific compound
depends on its molecular properties, treatment technology
implemented, and water quality and lifetime of the cartridge.
Keywords: perfluoroalkyl substance, pharmaceutical, point of use, POU, water treatment
More than 1.1 billion people are unable to access safe drinking
water (Sobsey et al. 2008). Even when clean water supply is available, compromised public pipes, old distribution systems, and
introduction of anthropogenic contaminants can lead to unsafe
water at the tap. Research suggests that improving water quality at
the point of use (POU) is more effective than upgrades at source
treatment plants in achieving a significant decrease in waterborne
disease (Clasen et al. 2007, Esrey et al. 1991). Because of a lack of
infrastructure to provide potable water, consumers in the developing
world must find alternate strategies to ensure safe drinking water
in the household (Greenstone & Hanna 2011). Although regulations for conventional contaminants exist and are more stringent
in the developed world, a growing percentage of the population is
suspicious of emerging contaminants and quality of tap water provided by crumbling distribution systems that are several decades
old (Gelt 1996). For these reasons, over the years POU devices have
been used in developing and developed countries to provide better
finished water quality from both a health and aesthetic perspective.
BACKGROUND
In 1999 the primary drinking water sources for 67% of US
residents were bottled water, POU devices, or both (WQA 1999),
and today nearly 40% of all US consumers use a water purification device (Mintel 2011). Several states allow for communities
to meet regulated water quality compliance through the use of
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POU devices (if proved to be effective) instead of centralized
treatment (NSF International 2010). For instance, Arizona and
Texas have permitted POU devices as a means for compliance for
arsenic and radionuclides (ADEQ 2005). In Washington, D.C.,
thousands of POU devices were distributed to treat high levels of
lead in drinking water (Edwards et al. 2009). Removal of radioactive elements using POU devices can be applied during emergencies and disaster zones (Sato et al. 2011) and was suggested
in Japan after the disaster at the Fukushima nuclear facility. In
developing countries, applications of POU devices in urban and
rural areas have shown dramatic reduction in microbial contaminants and metals, resulting in better water quality (Luoto et
al. 2011, Albert et al. 2010, Ngai et al. 2007).
A POU treatment device is any unit that is designed to improve
water quality by providing a barrier against both microbial and
chemical contaminants in water within a home (Mintel 2011, Miles
et al. 2009, Sobsey et al. 2008, Esrey et al. 1991). Several configurations of POU devices are commercially available, and technologies within a POU type device can be configured for a particular
water quality. Thus, POU devices offer a high degree of flexibility,
depending on the water quality to be treated and the desired produced water quality. Activated carbon-based POU devices are a
viable option for removal of both organic compounds, such as
pesticides, certain disinfection by-products, and some industrial
chemicals (Smith & El Komos 2009, Ahmedna et al. 2004a) and
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metals such as arsenic, copper, lead, and manganese (Carriere et
al. 2011, Deshomes et al. 2010, Moller et al. 2009, Ahmedna et
al. 2004b, Lin et al. 2002). Although the ability of these devices
to attenuate microbial and conventional chemical contaminants
has been shown, studies on their feasibility to treat emerging
organic contaminants are lacking. With increased anthropogenic
influence on source waters because of a burgeoning population
and limited availability of pristine water sources, contaminants
not previously expected in waters are being detected. Contaminants such as pharmaceuticals and hormones are being detected
in tap waters throughout the world (Félix-Cañedo et al. 2013,
Mak et al. 2009, Heberer 2002) and pose an unknown health risk
to a significant portion of the global population through chronic
exposure via drinking water.
Trace organic compounds (TOrCs). TOrCs are ubiquitous in the
aquatic environment through wastewater discharge, surface runoff, and other point and nonpoint source inputs (Benotti et al.
2009, Focazio et al. 2008, Kolpin et al. 2002). Also known as
contaminants of emerging concern, this group of compounds
includes pharmaceuticals, personal care products, endocrine
disruptors, and industrial compounds such as perfluoroalkyl
substances. Humans are often exposed to low concentrations of
TOrCs through drinking water because traditional treatment
processes generally are unable to ensure complete removal of
these substances (Benotti et al. 2009, Westerhoff et al. 2005).
While some TOrCs are known to affect wildlife at concentrations
occurring in wastewater discharge (Sanderson et al. 2004, Bevans
1995), the detection of most TOrCs at low ng/L concentrations
in potable water is not expected to pose an immediate threat to
public health (Bruce et al. 2010). However, synergistic and additive effects, long-term exposures, and low-dose impacts of individual and mixtures of TOrCs are largely unknown (Kim et al.
2009, Daughton & Ternes 1999).
Beyond those compounds currently monitored, additional
substances are certain to be detected as analytical technologies
continue to improve. In addition, new compounds are constantly
introduced into commerce, and others are formed through transformation within natural and engineered systems. Within the
United States, regulatory actions to determine acceptable concentrations of TOrCs in water are generally slow and often controversial (Novak et al. 2011), and most countries currently do not
have regulations in place for these compounds. For this reason,
many consumers have decided to use bottled water and/or POU
devices in hopes of gaining improved water quality and security,
from both health and aesthetic standpoints.
Treatment processes to attenuate TOrCs. Currently only advanced
water treatment processes such as advanced oxidation processes,
activated carbon, and desalting membranes such as reverse osmosis/nanofiltration are able to effectively attenuate most TOrCs’
resilience to conventional treatment such as coagulation and
chlorination (Anumol et al. 2015, Rosario-Ortiz et al. 2010,
Kimura et al. 2004). Advanced treatment approaches are rarely
applied, however, because they are often prohibitively expensive
and energy-intensive (Høibye et al. 2008, Jones et al. 2007). Furthermore, they require significant capital investment and upgrade
of existing infrastructure that is often unaffordable in developing
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countries (Roccaro et al. 2013). This is especially true for small
and isolated communities, some of which rely on small networks
of wells that are not always interconnected. Desalting membrane
processes such as reverse osmosis and nanofiltration are not only
energy-intensive but also generally result in a loss of water
through the creation of a waste stream from the consequential
brine. Activated carbon requires large amounts of thermal energy
to produce and regenerate and must be transported to and from
locations repeatedly. Advanced oxidation is particularly attractive but can lead to formation of toxic and uncharacterized
by-products (Heringa et al. 2011, Andrzejewski et al. 2008,
Von Gunten & Holgne 1994). Moreover, even the highest purity
of produced drinking water can be compromised in the distribution system through cross-connections, infrastructure failure, or
intentional perturbations (Cleland 2010).
Less than 1% of potable water generated in the United States
is used for drinking and cooking (Cotruvo 2003), which means
that most potable water is used as “service water” for nonpotable
purposes. Advanced water treatment to reduce emerging contaminants incurs significant costs, both financial and environmental. Given these realities, future safe drinking water paradigms
may shift toward providing the right quality of water for the
intended application; in other words, the highest quality water is
used for consumption and high-exposure use (i.e., bathing), and
the remaining water for nonpotable applications is treated to a
lesser standard to save energy, chemical, and infrastructure costs.
The aim of the current study was to determine the effectiveness
of five commercially available POU devices in removing a representative group of indicator TOrCs from two differing waters.
The TOrCs were selected as model compounds, representing a
larger class of organic compounds with diverse chemical structures and physical properties that may be present in drinking
water. The application of POU devices in attenuating these TOrCs
would be viable in both developed and developing countries to
ensure safe drinking water at the point of use.
MATERIALS AND METHODS
Selection of POU devices. This research tested three commercially available pitcher POU (P-POU) devices—the Brita® Riviera
eight-cup filter, 1 PUR™ CR-6000 seven-cup filter, 2 and
ZeroWater® eight-cup filter3—and two refrigerator-fitted POU
(R-POU) devices—the GE ® MSWF 4 and Whirlpool ®
W10295370 filter.5 R-POU and P-POU devices were selected
for testing because in the United States, nearly 40% of POU
users have an R-POU device and 38% own a P-POU device
(Mintel 2011). These POU devices are in use because they are
small, easy to install, and easy to transport to rural and hardto-reach regions. The individual POU brands were selected on
the basis of sales data provided by the Good Housekeeping
Research Institute in New York, N.Y. (Genovese 2011).
The P-POU devices all used activated carbon plus cation
exchange resins, with the ZeroWater also containing an anion
exchange resin (Brita 2015, Kaz USA 2013, Kellam 2012). While
the exact amount of activated carbon and ion exchange (IX)
resin in each filter is proprietary business information, a report
found that 60% of the Brita filter consisted of activated carbon,
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and the remaining was filled with a cation exchange resin (Dean
et al. 2010). The R-POU devices operated with solid block activated carbon (SBAC) technology and no IX resin. Each filter
had an exhaustion time specified by the manufacturer either as
volume of water passed through the filter or time of service; this
was termed the manufacturer’s expected lifetime (MEL). In
terms of volume of water, the MELs of the R-POU devices (GE
MSWF = 1,136 L, Whirlpool = 757 L) were an order of magnitude greater than those of the P-POU devices (Brita = 151 L,
PUR = 151 L, ZeroWater = 85 L). Each filter was tested in
duplicate or triplicate in accordance with NSF/ANSI Standard
53 guidelines (NSF International/ANSI 2007).
Selection of target compounds. The current research considered
16 indicator TOrCs selected on the basis of multiple criteria,
including their resistance to conventional drinking water treatment, frequency of detection in finished water, and ease of
analytical detection, as well as the representation of different
chemical properties and class of compounds. Eight of the compounds chosen for the study have since been added to NSF/
ANSI Standard 401 to test emerging contaminant removal by
POU/point-of-entry devices (NSF International/ANSI 2014).
Table 1 lists the TOrCs analyzed in this study and shows their
relevant chemical properties.
Selection of test waters. Two waters were included in this study. The
first, a potable water taken directly from the tap and originating from
groundwater in the city of Tucson, Ariz. (Tucson GW). The second
was a surface water from Colorado River water from the Central
Arizona Project (CAP) canal in Arva Valley, Ariz. (CAP water).
Experimental setup. Test waters were passed sequentially
through 10-, 5-, and 1-µm cartridge filters to remove any large
particles and then stored in a 2,000-L high-density polyethylene
tank and held at room temperature (25ºC) for the duration of
testing. The tank was mixed and aerated for 5 h to remove free
chlorine, which was measured for both waters by the DPD
method using a pocket colorimeter6 to ensure there was no free
chlorine in the tank.
Prior to beginning the experiment, each POU device was preconditioned with the test water as recommended by the manufacturer.
The general conditions for testing POU devices for organics
removal as stated in the NSF/ANSI Standard 53 were followed
(NSF International/ANSI 2007). Water was fed to the three P-POU
devices in 1-L increments followed by an equilibration time of 15
to 30 s before the subsequent 1-L addition. The R-POU devices
were connected to a centrifugal pump that passed water through
the devices at a fixed pressure of 35 to 40 psi. A calibrated flowmeter7 was used to monitor the volume of water passed through
each POU device, and the flow rates for each were monitored at
regular intervals. The test was discontinued after 150% of the MEL
or if the flow rate of a device fell below 20% of its initial flow.
Devices were operated for 10 h/d followed by a rest period of
14 h, during which the devices were stored at 4ºC. Water samples
of 1 L were collected in silanized amber glass bottles for each POU
device when the percentage of water passed through was equivalent
to 0, 25, 50, 75, 100, 125, and 150% of the MEL in accordance with
NSF/ANSI Standard 53 guidelines (NSF International/ANSI 2007).
These guidelines state that filters with a performance indication
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device must be operated to 120% MEL and those without a performance indicator to 200% MEL; as a compromise and to maintain consistency, all tests in the current research were stopped at
150% MEL. The MEL at 0% was considered to be after the preconditioning of the POU device with test water. Control samples
from the tank were collected at the same time to verify that no
degradation of the TOrCs had occurred during the experiment.
The average influent concentration of each TOrC after spiking for
all experiments was between 140 and 1,300 ng/L. Samples were
stored at 4°C immediately after collection.
Analytical methods. All samples were extracted using a solidphase extraction (SPE) technique previously published (Anumol
et al. 2013). Briefly, a 1-L sample was spiked with surrogate
standards at 100 ng/L and extracted using a 200-mg hydrophilic–lipophilic balance cartridge8 using an automated SPE
device.9 SPE cartridges were sequentially conditioned with 5 mL
each of methyl-tert-butyl-ether (MTBE), methanol, and ultrapure water and then loaded with the samples at 15 mL/min.
Cartridges were dried for 30 min using nitrogen and then
eluted with 5 mL of methanol followed by 5 mL of 90:10
(volume per volume) MTBE-to-methanol, followed by concentration to 500 µL and reconstitution to 1,000 µL in methanol for analysis.
Four different analytical methods were used to analyze the
TOrCs in the current study. All compounds were analyzed with
liquid chromatography using a binary pump10 while using two
separate detectors. A triple quadrupole mass spectrometer11
was used to analyze all pharmaceuticals and personal care
products, details of which are described elsewhere (Anumol et
al. 2013). Estrone and bisphenol A were analyzed using liquid
chromatography–mass spectrometry/mass spectrometry in
negative electrospray ionization mode, and a fluorescence detector was used to quantify the two alkylphenols—nonylphenol
(NP) and octylphenol (OP).
RESULTS AND DISCUSSION
TOrC breakthrough in P-POU filters. The P-POU devices were
effective in removal of TOrCs, but their performance and
removal efficiency depended on the brand of device, volume of
water treated, water quality, and chemical properties of the
individual TOrC. All P-POU devices were able to pass water at
an acceptable flow rate to the MEL for Tucson GW but only
the Brita filter managed to run until the experimental goal of
150% MEL; the PUR (125% MEL) and ZeroWater (110%
MEL) filters had drop in flow rate of greater than 80%, which
resulted in cessation of the test. In the CAP water, with a higher
TOC of 3.7 mg/L, all three P-POU devices had lower average
flow rates, but the Brita filter was able to reach the 150% MEL
whereas the ZeroWater filter ceased at its MEL. The PUR filter
suffered severe flow rate loss at 25% MEL in the CAP water,
and the experiments were stopped prematurely. The higher
TOC in the CAP water may also have affected the flow rates
of the filters. The ZeroWater filter flow was, on an average,
28% faster in the Tucson GW (91 mL/min) compared with CAP
water (65 mL/min), and flow for the Brita filter was more than
40% faster in the Tucson GW (332 mL/min) than in the CAP
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TABLE 1
Chemical properties and molecular structure of TOrCs studied
Compound
Use
pKa
Log Kow
Log Dow
(pH = 7.8)
Log Dow
(pH = 8.2)
Atrazine
Herbicide
1.7
2.3
2.3
2.3
Bisphenol Aa
Plasticizer
10.1
4.1
4.1
4.1
Carbamazepinea
Anti-seizure medication
13.9
2.8
2.6
2.6
DEETa
Insect repellant
0.7
2.5
2.5
2.5
Estronea
Steroid
10.4
4.3
4.3
4.3
Fluoxetine
Antidepressant
9.5
4.2
2.0
3.2
Ibuprofena
Analgesic
4.9
3.8
1.3
0.6
4-n-Nonylphenola
Surfactant degradate
10.7
5.7
5.7
5.7
4-n-Octylphenol
Surfactant degradate
10.4
5.3
5.3
5.3
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Structure
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TABLE 1
Chemical properties and molecular structure of TOrCs studied (continued)
Use
pKa
Log Kow
Log Dow
(pH = 7.8)
Log Dow
(pH = 8.2)
PFOA
Fluorosurfactant
2.8
5.1
1.8
1.8
PFOS
Fluorosurfactant
NA
5.4
3.1
3.1
Primidone
Anticonvulsant
11.6
1.1
1.1
1.1
Sucralose
Artificial sweetener
NA
–0.4
–0.3
–0.3
Sulfamethoxazole
Antibiotic
6.0
0.8
0.5
0
TCEPa
Flame retardant
NA
–1.2
–8.9
–9.7
Trimethoprima
Antibiotic
7.1
1.3
1.0
1.3
Compound
Structure
DEET—N,N-diethyl-meta-toluamide, NA—not available, PFOA—perfluorooctanoic acid, PFOS—perfluorooctane sulfonate, TCEP—tris(2-carboxyethyl)phosphine, TOrC—trace organic compound
aCompounds
are listed for testing in NSF/ANSI Standard 401 (NSF International/ANSI, 2014); pKa and log D values were calculated from ChemAxon (www.chemicalize.com).
water (181 ml/min). The average flow rate of the PUR filters
was also slower in the CAP water (104 mL/min) compared with
the Tucson GW (247 ml/min).
Because the filters varied in terms of lifetime and performance,
the authors used four criteria to compare and contrast the efficacy
of the different POU devices in attenuating TOrCs:
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•• The individual removal efficiency (IRE) is defined as
the removal of a specific TOrC at a given sampling
point.
•• The lifetime individual removal efficiency (LIRE) is defined
as the average removal of a specific TOrC throughout the
MEL (0–100% MEL).
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•• The overall removal efficiency (ORE) is defined as the average removal of all contaminants (∑TOrCs) at each sampling
point by each filter.
•• The lifetime overall removal efficiency (LORE) is defined as
the mean percent removal of all contaminants throughout
the MEL (0–100% MEL) of the filter.
The ORE and LORE for each filter in the two waters are
shown in Figure 1. At the 0% MEL sample in Tucson GW, the
Brita filter achieved >85% removal of ∑TOrCs whereas the PUR
and ZeroWater filters had nearly complete removal (>98%). At
100% of the MEL, the filters’ removal of all TOrCs in the Tucson
GW decreased in the following order: ZeroWater (93.2%) > PUR
(83.6%) > Brita (50.2%). In the CAP water, the OREs for all
three filters were similar as in the Tucson GW (Brita = 91.6%,
PUR = 98.5%, ZeroWater = 99.6%) at the initial sample point
(0% MEL); at 100% MEL, and the ORE for the Brita filter was
51%, whereas ZeroWater removals were 87.9%. The PUR filter
had greater than 98% ORE for the two sampling points (0 and
25% MEL) in the CAP water. Compared with the Tucson GW,
the LORE in the CAP water decreased by an average of 11% in
the Brita filter (70.7% versus 63.4%) and 4% in the ZeroWater
filter (94.9% versus 91.6%). Because the PUR filter clogged and
FIGURE 1
Overall removal efficiency of TOrCs by all POU devices in both water qualities
Tucson GW
Cap (SW)
Brita Filter
100
40
80
Removal—%
60
60
40
20
20
25
50
75 100 125 150 LORE
MEL—%
0
25
50
75 100 125 150 LORE
MEL—%
40
80
80
60
40
20
0
0
25
50
75 100 125 150 LORE
MEL—%
Whirlpool Filter
100
Removal—%
Removal—%
GE Filter
100
0
60
20
0
0
ZeroWater Filter
100
80
Removal—%
Removal—%
PUR Filter
100
80
0
was unable to pass water at 25% of its MEL, no removal was
assumed for the rest of its expected MEL in the CAP water, and
this resulted in a LORE of 38.9% (compared with 90.6% in
Tucson GW). The removal of all TOrCs in both the Tucson GW
and CAP water was measured, and reduction of nine representative TOrCs showing different behaviors is shown in Figure 2.
NP, OP, estrone, sucralose, and tris(2-carboxyethyl)phosphine
(TCEP). The three P-POU devices have two principal attenuation
strategies: adsorption by activated carbon and ion exchange by
IX resins. The pH-corrected log KOW known as the distribution
coefficient (log DOW) is generally used for assessing the adsorption of charged species at environmental pH. The high-log Dow
compounds such as NP (5.7), OP (5.3), and estrone (4.3) were
well removed by all P-POU devices throughout their life-spans,
in contrast to hydrophilic compounds such as sucralose (–0.3)
and TCEP (–1.2). For instance, in the Tucson GW, the LIRE of
the Brita filter for OP, NP, and estrone was 97.8, 91.9, and 89.5%,
respectively. In contrast, the Brita filter removed on average only
48.7% of sucralose and 69.3% of TCEP in Tucson GW throughout its lifetime.
Similar to the ∑TOrC removal, individual contaminant removal
was also negatively affected by the higher-TOC CAP water. This
60
40
20
0
25
50
75
100 125 150 LORE
0
0
25
50
MEL—%
75
100 125 150 LORE
MEL—%
CAP—Central Arizona Project, GW—groundwater, LORE—lifetime overall removal efficiency, MEL—manufacturer’s expected lifetime, POU—point-of-use,
SW—surface water, TOrCs—trace organic compounds
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FIGURE 2
Removal of nine representative TOrCs by all five POU devices
Trimethoprim
Sucralose
PFOA
PFOS
Carbamazepine
Fluoxetine
Octylphenol
Nonylphenol
Primidone
Brita
GE
CAP (SW)
Tucson GW
100
80
80
80
80
60
40
0
60
40
20
0
25
0
50 75 100 125 150
MEL—%
Removal—%
100
Removal—%
100
20
60
40
20
0
25
25
50
80
80
100
50
75 100 125 150
MEL—%
96
94
40
92
0
0
75 100 125 150
90
0
100
25
MEL—%
25
50
50
75 100 125 150
MEL—%
80
99
60
98
97
40
96
20
0
0
CAP (SW)
100
80
Removal—%
60
20
50
100
98
20
25
25
Tucson GW
Removal—%
100
Removal—%
100
0
0
Whirlpool
CAP (SW)
40
40
0
75 100 125 150
MEL—%
PUR
60
60
20
0
0
50 75 100 125 150
MEL—%
Tucson GW
Removal—%
CAP (SW)
100
Removal—%
Removal—%
Tucson GW
95
0
100
99
60
98
97
40
96
20
0 25 50 75 100125 150
25
50
75 100 125 150
0
95
0
25
0
50
MEL—%
25
50
75 100 125 150
MEL—%
ZeroWater
Tucson GW
100
80
100
Removal—%
Removal—%
80
60
90
40
80
20
60
40
20
70
0
CAP (SW)
100
0
25
0 25 50 75 100 125
50 75 100 125 150
MEL—%
0
0
25
50 75 100 125 150
MEL—%
CAP—Central Arizona Project, GW—groundwater, LORE—lifetime overall removal efficiency, MEL—manufacturer’s expected lifetime,
PFOA—perfluorooctanoic acid, PFOS—perfluorooctane sulfonate, POU—point-of-use, SW—surface water, TOrCs—trace organic compounds
For the sake of clarity, insets have been added to some graphs to provide a better scale for showing slight variations in TOrC removals.
GE filter results for all nine compounds in Tucson GW are shown at the top of the graph, but individual results cannot be discerned because they were
virtually identical. Similarly, for GE filter results in CAP water, some compounds were completely removed (100% removal) and are grouped so closely at the
top of the graph that individual results cannot be discerned.
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could be attributed to increased competition for pore sites on
the activated carbon between TOrCs and natural organic matter
(de Ridder et al. 2011). In the CAP water, the Brita filter LIREs
for OP and estrone dropped to 95.1 and 72.5%, respectively, and
the LIREs for sucralose and TCEP dropped to 36.7 and 55.4%,
respectively. The ZeroWater filter showed similar trends, but
compared with the Brita filter demonstrated higher IREs at each
MEL in both waters. The LIREs of the ZeroWater filter for
estrone, sucralose, and TCEP were 100, 85, and 92.4%, respectively, in Tucson GW and 98.5, 67.7, and 78.9%, respectively, in
CAP water. OP was completely removed throughout the experiment in both waters by the ZeroWater filter. The lifetime removal
of NP by the ZeroWater and Brita filters increased slightly in CAP
water to 100 and 93%, respectively, compared with 93.2 and
92%, respectively, in the Tucson GW; this increase may be attributable to the high sorption capacity of NP to dissolved organic
matter (Düring et al. 2002), which allowed for marginally better
removal by the filter. In the Tucson GW, the PUR filter had LIREs
of 98.8, 94.8, 100, 81.3, and 90.9% for OP, NP, estrone, sucralose, and TCEP, respectively. Because of the early stoppage of the
PUR filter in the CAP water, it was difficult to make any significant observations, but the filter removed greater than 94% of all
five compounds at both sampling points (0 and 25% MEL).
Fluoxetine, atrazine, perfluorooctane sulfonate (PFOS), and
perfluorooctanoic acid (PFOA). The cation exchange resins present
in the three pour-through P-POU devices enhanced the removal of
charged species in both test waters. Fluoxetine (pKa = 10.4, log
Dow = 2.0) was primarily in cationic form in the Tucson GW
(pH = 7.8), and its removal by all three P-POU devices was higher
than removal of the neutral atrazine (pKa = 1.7) with a similar
log Dow of 2.3. In the Tucson GW, the LIREs of fluoxetine for
the Brita, PUR, and ZeroWater filters were 83.9, 97.8, and
99.6%, respectively, whereas atrazine removals for the three filters were 63.3, 89, and 93.6%, respectively. Removal of fluoxetine and atrazine by the three P-POU devices followed a similar
trend in the CAP water (pH = 8.2).
The LIREs of the two perfluoroalkyl substances—PFOS and
PFOA—were lower than most other compounds for the Brita filter
(57 and 52%, respectively) and PUR filter (84.8 and 79.4%,
respectively), but PFOS and PFOA were well removed by the
ZeroWater filter (96.7 and 97.5%, respectively). PFOS and PFOA
are dominantly present in their anionic form in the environment
(Kissa 1994). The presence of an anionic exchange resin in the
ZeroWater P-POU device allowed greater removal of PFOS and
PFOA, compared with the Brita and PUR P-POU devices in the
two waters. As these cases illustrate, the octanol–water partition
coefficient may be a good indicator for removal of nonionic species,
but information on individual compound pKa values as well as the
solution pH is essential to understand actual removal in activated
carbon-based POU devices that also incorporate IX resins.
TOrC breakthrough in R-POU filters. In line with the manufacturer’s specifications, the two refrigerator filters in this study were
operated at much higher flow rates and treated greater volumes
than the P-POU filters. In the Tucson GW, both R-POU filters,
operated at constant pressure, maintained flow rates in excess of
1.4 L/min throughout the experiment, with an average flow rate
JOURNAL AWWA
of >1.6 L/min for the GE filter and 1.5 L/min for the Whirlpool
filter. Similar to the P-POU devices, the flow rate of both R-POU
devices was negatively affected by the CAP water. Although the
GE filter reached the experimental goal of 150% MEL in both
waters, its average flow rate was 1.3 L/min in the CAP water
(~20% reduction compared with the Tucson GW). Similar to the
PUR P-POU filter, the flow rate of the Whirlpool R-POU device
in the CAP water was significantly reduced from 1.6 L/min to
below 0.4 L/min, resulting in termination of the experiment just
before 50% MEL (48%).
The two R-POU devices were very effective (>96%) at removing TOrCs in the Tucson GW at each sampling point throughout
the experiment. The GE filter had OREs between 96.9 and 99.6%
throughout the experiment in the Tucson GW with a LORE of
98.4%. The Whirlpool filter had OREs between 96.8 and 99.7%
and average removal of 99% throughout its MEL. On the basis
of this testing, both R-POU devices would pass the requirements
for the NSF/ANSI Standard 401 testing for emerging contaminant
removal in the Tucson GW (NSF International/ANSI 2014).
TOrC removal efficiency of both R-POU devices was negatively
affected by the constituents of the CAP water; for the GE filter
in the CAP water, OREs were between 83.3 and 99.9% throughout the MEL, with a LORE of 90.1%. Removal efficiency
declined steadily with volume of water passed through the GE
filter, resulting in a 17% reduction in removal efficiency of TOrCs
from 0% through to 100% MEL in the CAP water. There was
continued gradual decline in performance past the MEL with an
ORE of 74% at the end of the experiment (150% MEL). The
ORE of the Whirlpool filter in the CAP water from start to
exhaustion (48% MEL) was 97.1 to 99.9% at the three sampling
points. However, the Whirlpool filter was unable to reach even
half its expected MEL in this water quality because of flow rate
decline; therefore, the LORE was 59.3% because no removal was
assumed from 50 to 100% MEL for this filter.
Although specific information on average particle size and
distribution of the carbons was not available, both R-POU devices
use SBAC, which is packed with much smaller particle sizes of
carbon than the loosely packed carbon in P-POU devices. Hence,
the R-POU devices have larger surface areas, allowing for greater
physical adsorption of organic contaminants. Both the GE and
Whirlpool R-POU devices are listed as NSF certified Class I
particulate-reduction devices by the manufacturers, meaning that
according to NSF/ANSI Standard 42, these POU devices are
certified to reduce at least 85% of particles from 0.5 to <1 µm in
size (NSF International/ANSI 2012). The smaller carbon particle
sizes could result in higher carbon surface area, which provides
more binding capacity for TOrCs than does the loosely packed
carbon in the P-POU devices. Additionally, the source of carbon
used to make the two types of POU devices may be different and
could be a contributing factor to TOrC removal.
NP, OP, estrone, sucralose, primidone, PFOS, PFOA, ibuprofen,
and sulfamethoxazole. Both R-POU devices had LIREs of >89%
for all contaminants tested in the Tucson GW. The hydrophobic
alkylphenols (NP, OP) were completely removed by the GE filter
in both waters and by the Whirlpool filter in the Tucson GW
throughout the experiment (150% MEL). The Whirlpool filter also
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JOURNAL AWWA
half the mass rejection (0.27 mg) compared with the other two. The
MLR of all P-POU devices was lower in the CAP water, indicating
a loss of performance in higher TOC water.
MLR = (∑TOrC Cin × LIRE) × Vol (up to 100% MEL)
(1)
in which MLR is the mass loading rejection (mg), Cin is the
influent concentration (mg/L), and Vol is the volume of water
treated (L).
The refrigerator filters were more effective than the pitcher
(pour-through) filters in terms of both TOrC attenuation at each
percent MEL and overall mass rejection. The LOREs of the GE
and Whirlpool filters in the Tucson GW were 98.7 and 99.2%,
respectively, compared with 70.7, 90.6, and 94.9% for the Brita,
PUR, and ZeroWater P-POU devices, respectively. The GE R-POU
filter was able to treat approximately 10 times the volume of the
P-POU filters, and the Whirlpool filter treated five times as much
in the Tucson GW and twice as much in the CAP water. In terms
of MLR, the GE filter was able to remove 7.56 mg of TOrCs in
the Tucson GW, which was greater than seven, 10, and 12 times
more than the PUR, Brita, and ZeroWater filters, respectively. The
Whirlpool R-POU filter had a slightly greater LORE than the GE
filter in the Tucson GW but treated only 67% of the volume of
water and had an MLR of 5.06 mg. Like the P-POU devices, both
R-POU devices were negatively affected by the CAP water, with
6.81 and 2.43 mg of MLR achieved by the GE and Whirlpool
R-POU devices, respectively.
Cost comparison of POU treatments. Eventually, the use of POU
devices to provide additional attenuation of contaminants in water
will be determined by their economic feasibility in comparison with
use of bottled water and other newer water treatment technologies
on the market. With this in mind, a cost comparison of the different
FIGURE 3
10
Mass load rejection (mg) of all five POU devices in both
water qualities
Tucson GW
CAP (SW)
7.58
8
6
MLR—mg
removed >98% of these two contaminants in the CAP water at all
three sampling points. In the CAP water, the GE R-POU device had
LIREs that were higher for the hydrophobic compounds such as
NP (100%), OP (100%), and estrone (99.8%) and lower for nonionic hydrophilic compounds such as sucralose (63.1%) and
primidone (91%). This reduction in removal efficacy was greater
at later MELs (especially after the 100% MEL), with average
removals of only 24.5 and 62% observed for sucralose and primidone, respectively. The Whirlpool filter had higher IREs of sucralose compared with the GE filter in the CAP water at corresponding MELs but was not able to reach even half the MEL because of
poor flow rate. The absence of IX resins in the R-POU devices may
have hindered the LIREs of ionized TOrCs, especially in the CAP
water. The lifetime removals of fully or partly ionic species such as
PFOS (49.3%), PFOA (66.6%), ibuprofen (84%), and sulfamethoxazole (73.4%) by the GE POU device in the CAP water
were significantly lower than for uncharged TOrCs. The removal
efficiency for ionic species seemed to follow a pattern based on
proportion of compound present in ionic form. On the basis of
pKa values, less than 20% of sulfamethoxazole and ibuprofen were
present in their charged form in the CAP water, whereas PFOA and
PFOS were entirely in their anionic form. Therefore, better removal
of sulfamethoxazole and ibuprofen compared with PFOS and
PFOA may be attributable to the adsorption of the neutral form
of these compounds by the SBAC even though their log Dow values
are smaller. Although the R-POU devices did not have any IX
resins, electrokinetic adsorption may have accounted for some
anionic species removal whereas physical/mechanical adsorption
because of enhanced surface area and more uniform size distribution of carbon in SBAC POU devices may also have assisted in
removal of these contaminants.
Summary of POU device efficacy. All POU devices were shown to
be effective in attenuating a wide variety of TOrCs in the test waters.
The range of removal efficacy depended on the type of POU device,
the water quality, the volume treated, and the chemical properties
of the specific trace contaminant. The ZeroWater P-POU device was
the best-performing pitcher filter in terms of LORE, with >92% in
the Tucson GW and >87% in the CAP water throughout the
experiment. However, the ZeroWater P-POU filter was rated to treat
only about 58% of the Brita and PUR filters; a comparison of
overall average removals on a volume-treated basis showed that the
PUR and ZeroWater filters had very similar removals (94.6%) in
the Tucson GW, whereas the Brita filter had >80% removal at the
same volume. Removals by both the Brita and ZeroWater filters
were reduced in the CAP water, and the PUR filter was able to pass
water at an acceptable flow rate to only 25% of its MEL. To
account for the different volume of water treated by each filter, mass
load rejection (MLR) was calculated for each POU device as shown
in Eq 1 and presented in Figure 3. The MLR can be defined as the
total mass of contaminants rejected by the filter during its specified
lifetime (0–100% MEL). The MLR of the three P-POU devices in
Tucson GW showed that the PUR filter had highest mass rejection
(0.99 mg) followed by the Brita (0.74 mg) and ZeroWater (0.59
mg). However, in the CAP water, the Brita filter had the greatest
mass rejection (0.66 mg) closely followed by the ZeroWater (0.56
mg), whereas the PUR filters’ early stoppage resulted in less than
5.06
4
2
1.0
0.8
0.99
0.74
0.59
0.6
0.4
0.66
0.2
6.81
2.42
GE
Whirlpool
0.56
0.27
0.0
Brita
PUR
ZeroWater
MEL—%
CAP—Central Arizona Project, GW—groundwater, MLR—mass load
rejection, POU—point-of-use, SW—surface water
2015 © American Water Works Association
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TABLE 2
Cost comparison of five POU devices
Brita Riviera
PUR CR-6000
ZeroWater
Eight-Cup Filter
GE MSWF
Whirlpool W10295370
32.99
21.99
33.99
700–3,000
410–2,500
8
7
8
NA
NA
Replacement filter cost—$
7.99
10.99
14.99
41.99
39.99
Filter lifetime—L
757
Parameter
Estimated capital costa—$
Capacity—cups
151
151
85
1136
Recommended filter replacement—months
2
2
2
6
6
Average filter lifetimeb—days
19
19
11
142
95
Annual cost of ownershipc—$
153
211
498
109
154
0.05
0.07
0.17
0.04
0.05
Annual cost per liter
treatedb—$/L
NA—not applicable, POU—point-of-use
aCost
of purchasing either the pitcher filter or a compatible refrigerator (data from manufacturer’s website)
a family of four consuming 2 L/d each
cost of ownership does not consider the capital cost of the refrigerator
bAssuming
cAnnual
POU devices was conducted with respect to capital required, cost of
replacement filters and annual cost of ownership (Table 2).
The annual cost of ownership was calculated on the basis of
the cost of a replacement filter (with the assumption that the
filter will run for its MEL and will be used by a family of four,
each consuming 2 L/d of water). Because of the high variability
in the cost of purchasing a refrigerator or other similar device to
operate the R-POU units, the annual cost of ownership did not
consider the capital cost (though estimated capital cost is included
in Table 2). Furthermore, the consumer may already own a refrigerator, the cost of which will be offset by the other ancillary
benefits it provides. The GE R-POU device had the lowest annual
cost at $109, followed closely by the Brita P-POU filter ($153)
and Whirlpool R-POU device ($154). The ZeroWater P-POU
filter ($498) had the highest annual cost, primarily because of its
lower expected lifetime in terms of volume of water treated,
which would necessitate more frequent replacement of the filter.
When costs per liter of water treated were compared, all of the
POU devices had annual costs below $0.20/L.
While a basic cost analysis is provided here, it is not in the scope
of this article to provide a detailed assessment of the economic
suitability and environmental sustainability of these devices. The
authors encourage further study into a cradle-to-grave analysis of
POU technologies, including detailed life cycle assessment of these
devices and cost comparisons with bottled water and other
advanced treatment technologies for providing high quality water.
CONCLUSION
This study demonstrated that POU devices have the ability to
reduce the concentration of a diversity of emerging organic chemical contaminants in potable water, complementing the removal
of metals, inorganics, and microbes researched by others (Sato et
al. 2011, Deshomes et al. 2010, Miles et al. 2009). Furthermore,
these devices provide an additional barrier to accidental or intentional contamination that may occur in the distribution system,
such as cross-connections, loss of pressure, or acts of terrorism
(Zhong et al. 2012). The results presented here indicate that POU
devices can be considered as an alternative to full-scale treatment
JOURNAL AWWA
processes as a means of attenuating trace organic compounds in
regions that have poor infrastructure and are in need of clean
drinking water. The application of POU devices may also be considered an additional final barrier in water treatment to provide
the highest-quality drinking water to concerned consumers and
to increase public confidence, especially when impaired source
waters are used, such as in potable water reuse applications. Certainly any benefits are conditional on the proper maintenance and
timely replacement of POU components as specified by the manufacturer. Previous studies have shown the cost-effectiveness of
POU devices compared with installation of a centralized unit
process to achieve a particular water quality (Quintana et al. 2010).
However, further cost–benefit analysis is required to understand
the life-cycle costs and benefits of a POU system. In light of global
water sustainability challenges of water quality and quantity, POU
devices could lead to a paradigm shift that allows for more appropriate use of the highest-quality water versus service water.
ACKNOWLEDGMENT
This study was funded in part by the Good Housekeeping
Research Institute in New York, N.Y. The authors thank Armando
Durazo, Colin Richards, and Amanda Veitch from the University
of Arizona (Tucson) for assistance with solid-phase extraction of
the samples. The authors also acknowledge Jeffrey Bliznick and
Gaylen Bennett at the Environmental Research Laboratory of the
University of Arizona for help in setting up the experiments. The
authors are grateful to Agilent Technologies (Santa Clara, Calif.)
and especially Joe Weitzel for providing instrumentation and
technical support used in this work.
ABOUT THE AUTHORS
2015 © American Water Works Association
Tarun Anumol is a liquid chromatography/
mass spectrometry applications scientist at
Agilent Technologies in Wilmington, Del. At
the time of this study, he was a PhD student
in the Department of Chemical and
Environmental Engineering at the University
of Arizona from which he graduated in
SEPTEMBER 2015 | 107:9
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Anumol et al. | http://dx.doi.org/10.5942/jawwa.2015.107.0129
Peer-Reviewed
August 2014. In addition to holding a doctorate, Anumol holds
a master of science degree in civil and environmental
engineering from Carnegie Mellon University in Pittsburgh, Pa.,
and a bachelor of technology degree in chemical engineering
from Anna University in Chennai, India. Bradley O. Clarke is a
senior lecturer at RMIT University in Melbourne, Australia.
Sylvain Merel is a research professor at the University of
Tübingen in Germany. Shane A. Snyder (to whom
correspondence may be addressed) is a professor in the
Department of Chemical and Environmental Engineering,
University of Arizona, 1133 E. James E. Rogers Way, Tucson,
AZ 85721 USA; [email protected].
Brita, 2015. See What We Filter Out of Your Tap. www.brita.com/why-brita/whatwe-filter/ (accessed June 15, 2015).
Bruce, G.M.; Pleus, R.C.; & Snyder, S.A., 2010. Toxicological Relevance of
Pharmaceuticals in Drinking Water. Environmental Science & Technology,
44:14:5619. http://dx.doi.org/10.1021/es1004895.
Carriere, A.; Brouillon, M.; Sauve, S.; Bouchard, M.F.; & Barbeau, B., 2011.
Performance of Point-of-Use Devices to Remove Manganese From Drinking
Water. Journal of Environmental Science and Health Part A: Toxic/
Hazardous Substances and Environmental Engineering, 46:6:601. http://dx.
doi.org/10.1080/10934529.2011.562852.
Clasen, T.; Schmidt, W.P.; Rabie, T.; Roberts, I.; & Cairncross, S., 2007.
Interventions to Improve Water Quality for Preventing Diarrhoea: Systematic
Review and Meta-Analysis. BMJ: British Medical Journal, 334:7597:782.
http://dx.doi.org/10.1136/bmj.39118.489931.BE.
PEER REVIEW
Date of submission: 03/25/2015
Date of acceptance: 05/28/2015
Cleland, C.A., 2010. Security and Preparedness—Threats and Investment Options to
Protect Our Drinking Water Distribution Networks. Journal AWWA, 102:12:36.
ENDNOTES
1Brita®
Riviera, Brita LP, Oakland, Calif.
CR-6000, Kaz USA, Southborough, Mass.
eight-cup filter, Zero Technologies, Bensalem, Pa.
4GE® MSWF, General Electric, Fairfield, Conn.
5Whirlpool® W10295370, Whirlpool, Benson Harbor, Mich.
6Hach, Loveland, Colo.
7McMillan Flow Products, Georgetown, Tex.
8Waters Corp., Milford, Mass.
9Dionex, Sunnyvale, Calif.
10Model 1290, Agilent, Palo Alto, Calif.
11Model 6460, Agilent, Palo Alto, Calif.
2PUR™
3ZeroWater®
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