Guidelines for Canadian drinking water quality boron: Analytical and treatment considerations

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Analytical methods to detect boron

Standardized methods

Standardized methods available for the analysis of total boron in drinking water and their respective MDLs are summarized in Table 3. MDLs are dependent on the sample matrix, instrumentation, and selected operating conditions and will vary between individual laboratories. These methods are subject to a variety of interferences, which are outlined in detail in the respective references. Analysis of boron should be carried out as directed by the responsible drinking water authority. Drinking water utilities should discuss sampling requirements with the accredited laboratory conducting the analysis to ensure that quality control procedures are met and that minimum reporting levels are low enough to ensure accurate monitoring at concentrations below the maximum acceptable concentration (MAC).

Table 3. Standardized methods for the analysis of boron in drinking water
Method (reference) Methodology MDL (µg/L) Interferences/comments
U.S. EPA methods

EPA 200.5 Rev. 4.2

(U.S. EPA, 2003)

Axially viewed inductively coupled plasma - atomic emission spectrometry (AVICP-AES) (wavelength 249.68 nm)


Matrix interferences: Ca, Mg and Na > 125 mg/L and Si > 250 mg/L

EPA 200.7 Rev. 4.4

(U.S. EPA, 1994)

Inductively coupled plasma - atomic emission spectrometry (ICP-AES) (wavelength 249.68 nm)


Matrix interferences: TDS > 0.2% weight per volume (w/v)

American Public Health Association (APHA) standard methods

SM 3120B

(APHA et al., 2017)

Inductively coupled plasma - atomic emission spectrometry (ICP-AES) (wavelength 249.77 nm)


Matrix interference: TDS > 1 500 mg/L

SM 3125

(APHA et al., 2017)

Inductively coupled plasma - mass spectrometry (ICP-MS)


ICP-MS method can be applied successfully for boron determination even though it is not specifically listed as an analyte in the method (as cited in SM 4500B A)

SM 4500-B.B

(APHA et al., 2017)

Colorimetric method using curcumin reagent and spectrophotometer (540 nm)

0.2Table 3 Footnote a

Applicable for boron concentrations in a range from 0.1 to 1.0 mg/L.

Interference: Na > 20 mg/L and hardness >100 mg/L as CaCO3

SM 4500-B.C

(APHA et al., 2017)

Colorimetric method using carmine reagent and spectrophotometer (585 nm)

2Table 3 Footnote a

Applicable for boron concentrations in a range from 1.0 to 10 mg/L.

Less sensitivity and requires the use of concentrated sulphuric acid.

International Organization for Standardization (ISO) methods

ISO 9390

(ISO, 1990)

Water quality - determination of borate-spectrophotometric method using azomethine -H

(414 nm)


Applicable for boron concentrations ranging from 0.01 to 1.0 mg/L

MDL – method detection limit; N/A – not available; TDS – total dissolved solids; SM – standard method

Table 3 Footnote a

Minimum detectable quantity

Table 3 Return to footnote a referrer

Online and portable colorimetric field kits

Commercial online and portable test kits are available for quantifying dissolved boron in source and drinking water and are generally based on colorimetric azomethine-H and carmine methods (ISO, 1990; APHA et al., 2017). The commercial online analyzers are capable of continuously measuring boron concentrations in the range of 0 µg/L to 500 µg/L with higher concentrations (up to 50 mg/L) requiring dilution. Portable test kits can be used to obtain a rapid measurement of boron concentrations in drinking water. In general, available commercial test kits using the azomethine-H method are capable of measuring boron concentrations in the range of 0.05 mg/L to 2.5 mg/L, while the carmine method is applicable for concentrations in the range of 0.2 mg/L to 14 mg/L. To accurately measure boron using these units, utilities should develop a quality assurance and quality control (QA/QC) program such as those outlined in Standard Method (SM) 3020 (APHA et al., 2017). Periodic verification of results using an accredited laboratory is recommended.

Sample preservation and preparation

Total boron includes both the dissolved and particulate (suspended) fractions of boron in a water sample and is analyzed using methods for total recoverable boron. Analysis of total boron is needed for comparison to the MAC.

Sample processing considerations for analysis of boron in drinking water (that is, sample preservation, storage, digestion) can be found in the references listed in Table 3. Accurate quantification of dissolved, particulate and total metals in samples is dependent on the proper sample preservation and processing steps. SM 3030B and SM 3030D provide guidance on filtration, preservation (acidification) and digestion procedures for the determination of dissolved or particulate metals (APHA et al., 2017). To determine dissolved boron concentrations, samples should be filtered at the time of collection (not at the laboratory) and the filtrate should be acidified to pH < 2 with concentrated nitric acid.

Treatment considerations

Published data on boron removal in water are primarily from seawater desalination and geothermal water treatment plants (Kabay et al., 2015). These data show that drinking water treatment technologies that are effective for boron removal are reverse osmosis (RO) and ion exchange (IX) using boron-selective resins (BSRs) and combinations of these processes (Kabay et al., 2010; Hilal et al., 2011; Farhat et al., 2013; Guler et al., 2015). Information on the removal efficiencies of boron and the operational conditions of treatment plants are reported below as they provide an indication of the effectiveness of treatment technologies for boron removal (see Tables 4 and 5).

As discussed in the section on Exposure, in the areas of Canada where boron is found in groundwater, concentrations are generally below 5 mg/L with maximum concentrations reaching 8 mg/L. Since this water quality will be significantly different than seawater, adjustments to the typical operation of the desalination plants reported below may be needed. However, studies have shown that process modifications used to increase boron removal in desalination and geothermal applications are also effective for groundwater systems (Rodriguez Pastor et al., 2001; Georghiou and Pashalidis, 2007; Kheriji et al., 2015).

The selection of an appropriate treatment process for a specific water supply will depend on many factors, including the raw water source and its characteristics, the operational conditions of the selected treatment method and the utility's treatment goals. Pilot testing is recommended to ensure the source water can be successfully treated. In addition, treatment plants should be aware that RO and IX generate liquid waste (for example, reject water or regeneration waste brine) that may require special handling and off-site disposal.

Boron chemistry

The species of boron present in water entering a treatment plant is an important factor in determining the effectiveness of treatment as smaller, neutral species are generally more difficult to remove than larger, charged species. The 2 main species of boron present in natural waters are boric acid (B(OH)3) and borate (B(OH)4-). The distribution of these species is controlled predominantly by pH with ionic strength and temperature also having a minor effect (Hilal et al., 2011; Kochkodan et al., 2015). In fresh water (temperature = 25o C) at pH below 9.2 the major species is boric acid and at higher pH borate is the major species (Kabay et al., 2010; Hilal et al., 2011; Kochkodan et al., 2015). Since most source waters have a pH lower than 9.2, boric acid is the predominant species that will need to be considered in drinking water treatment systems.

Municipal scale

The selection of an appropriate treatment process will depend on many factors, including the raw water source and its characteristics, the operational conditions of the selected treatment method and the water utility's treatment goals. Treatment goals may require that pH be adjusted post-treatment to address corrosion issues in the distribution system (Health Canada, 2015). Pilot- and bench-scale testing is recommended to ensure the source water can be successfully treated and to optimize operating conditions.

Boron is not removed by drinking water treatment technologies commonly used for surface and groundwater sources such as chemically assisted filtration and/or chlorination (Parks and Edwards, 2005; Tagliabue et al., 2014). Therefore, alternative treatment processes, such as those discussed below, are needed for boron removal.

Reverse osmosis (RO)

RO is the most widely used process for boron removal (Guler et al., 2015; Kabay et al., 2018a). When boron is present as borate (B(OH)4-) in source water, it is effectively rejected (> 95% removal) using standard RO membranes by diffusion and charge repulsion by negatively charged membranes (Bodzek et al., 2015; Guler et al., 2015). However, when boron is predominantly in the form of boric acid (pH < 9.2) rejection is lower (40% to 70%) because it is a smaller, neutral species (Magara et al., 1996; Hilal et al., 2011; Farhat et al., 2013; Bodzek, 2015; Guler et al., 2015; Kabay et al., 2015). Therefore, design and process modifications are needed to standard RO systems to achieve low treated water boron concentrations when boron is present as boric acid in source water.

The most common approaches for boron removal using RO are single and multi-pass RO, RO with increased pH, and the use of high boron rejection membranes or a combination of these processes (Redondo et al., 2003; Hilal et al., 2011). The key parameters that affect boron removal using RO include feed water quality (pH, temperature, total dissolved solids), properties of the membrane and system design and operation (average permeate flux, recovery and operating pressure) (Redondo et al., 2003; Guler et al., 2011; Tomaszewska and Bodzek, 2013; Viatcheslav et al., 2015). Boron removal data from pilot and full-scale treatment plants is reported in Table 4.

Single-pass RO is the simplest system to design and operate for boron removal. Full-scale treatment plants using single-pass seawater reverse osmosis (SWRO) have been shown to decrease boron concentrations of up to 5 mg/L to approximately 0.9 to 1.8 mg/L in treated water (65% to 85% rejection), depending on the membrane type and recovery ratio of the system (Kabay et al., 2010; Viatcheslav et al., 2015). Data presented in Table 4 indicate the operational conditions used by treatment plants to achieve treated water concentrations well below 5 mg/L (range of 0.25 to 2 mg/L). Various modifications can increase boron removal in existing RO treatment plants. These include increasing the feed water pH, adding a second pass coupled with pH adjustment, and passing the feed water through an ion exchange system (Glueckstem and Priel, 2003; Viatcheslav et al., 2015). Several authors have noted that low boron concentrations (< 0.5 mg/L) are rarely reached for single-pass reverse osmosis seawater desalination plants equipped with standard commercially available RO membranes (Hilal et al., 2011; Guler et al., 2015; Kabay et al., 2015; Kabay et al., 2018a).

A study in Saskatchewan determined boron removal efficacy at 22 water treatment plants with various treatment technologies. Seventy percent (15) of treatment plants were supplied by groundwater and 31% (7) of the treatment plants were equipped with RO systems. Monitoring data from 2016 to 2021 showed that 26% of all systems had raw water boron levels greater than 2 mg/L. Study results showed that all the RO systems were capable of removing boron. Removals ranged from 8% to 44% for raw water concentrations of 0.5 mg/L to 3.5 mg/L, resulting in treated water concentrations of 0.4 mg/L to 3.1 mg/L for these full-scale systems (Thirunavukkarasu and Bansah, 2022). These results indicate that some existing full-scale RO systems that are not specifically designed for boron removal require modifications or additional resources to achieve boron concentrations below 5 mg/L.

An important consideration for water utilities is selection of an appropriate membrane, particularly for single-pass RO systems, because boron rejection (removal) varies considerably depending on the properties of the membranes used in the system. Under standard laboratory test conditions brackish water RO membrane boron rejection ranges from 40% to 80% and standard SWRO membrane boron rejection ranges from 82% to 92% (Redondo et al., 2003; Gorenflo et al., 2007; Kabay et al., 2010; Tu et al., 2010). In comparison, high boron rejection membranes can achieve removals from 93% to 96%, but these membranes usually have higher feed pressure requirements (Guler et al., 2015; Viatcheslav et al., 2015). These membranes are commercially available and may be appropriate when source water concentrations of boron are high.

Table 4. Boron removal reported in pilot and full-scale reverse osmosis treatment plants
Influent (mg/L) Effluent (mg/L) Rejection (%) Process description Operating conditions Reference
Single-pass RO




Single-pass SWRO treatment of seawater (full-scale)

  • P: 39.3 bar
  • T: 12.8 oC
  • Recovery: 50%
  • Permeate flow rate: 155 m3/h
  • pH: 7.3

Busch et al. (2003)




Single-pass SWRO treatment of seawater (full-scale)

  • P: 801 psi
  • T: N/A
  • Recovery: 50%
  • Permeate flow rate: 17.2 gpm
  • pH: 6.69-8.03

Kim et al. (2009)



91.5% (average)

Single-pass SWRO treatment of seawater (full-scale)

  • P: 63.5 bar
  • T: 22 oC
  • Recovery: 36%
  • Permeate flow rate: 1200 m3/h
  • pH: 7.0

Busch et al. (2003)




Single-pass SWRO with standard membranes (full-scale)

  • P: 6.5-7.5 MPa
  • T: 18-26 oC
  • Recovery: 37%-47%
  • Permeate flow rate: 7200 m3/d
  • pH: 8

Ruiz-Garcia et al. (2019)



Single-pass SWRO with high boron rejection membranes (full-scale)



56% (average)

Single-pass BWRO treatment of geothermal water (pilot-scale)

  • P: 1.1 MPa
  • T: 30 oC
  • Recovery: 75%-78%
  • Permeate flow rate: 1 m3/h
  • pH: 5

Tomaszewska and Bodzek (2013)

2-pass or 2-stage RO





2-pass low-pressure BWRO treatment of geothermal water (pilot-scale)

  • P: 1.0 MPa
  • T: 30 oC
  • Recovery: 75%
  • Permeate flow rate: 1 m3/h
  • pH: 1st pass acidified to pH 5 (to prevent scaling), 2nd pass pH increased to 10-11

Tomaszewska and Bodzek (2013)




2-stage SWRO treatment of seawater

1st stage using high pressure SWRO boron rejection membranes

2nd stage lower pressure SWRO membranes (full-scale).

  • P: N/A
  • T: 14-27oC
  • Recovery: 50%
  • Permeate flow rate: 515 m3/h
  • pH: stage 1 feed pH 8.0 increased to 8.6 during summer (27 oC); 0.9 to 1.3 mg/L anti-scalant added

Franks et al. (2013)




(normalized rejection over two stages)

2-stage high recovery RO plant using SWRO membranes (full-scale)

  • P: 59-66 bar
  • T: 22oC
  • Recovery: 55%
  • Permeate flow rate: 295 m3/h
  • pH: feed acidified to 7.0-7.3

Redondo et al. (2003)

Multi-stage (that is, 3+) RO


< 0.3


(across all stages)

Multi-stage cascade SWRO treatment of seawater

Part of 1st stage RO permeate treated in 2nd stage with high pH, low recovery

Concentrate from 2nd stage treated in 3rd and 4th stage to remove hardness and additional boron (full-scale)

P (normalized): 7.3-11 bar (2nd stage), 8.5-12 bar (3rd stage), 8.2-10.5 (4th stage)

T: 19-32 oC

Recovery (overall): > 95%

Permeate flow rate:

330, 000 m3/d

pH: 7-8 (1st stage), 10 (2nd stage), 6.5 (3rd stage), > 10 (4th stage)

Gorenflo et al. (2007)

BWRO – brackish water reverse osmosis; N/A – not available; P – feed pressure; RO – reverse osmosis; T – temperature; SWRO – seawater reverse osmosis

In cases where greater boron removal needs to be achieved, more complex RO systems (for example, multi-pass RO system [with or without pH adjustment]) need to be installed (Tomaszewska and Bodzek, 2013; Viatcheslav et al., 2015). A variety of design configurations have been used and are reported in Hilal et al. (2011). The most common approach is to use a 2-pass RO system with an increase in pH prior to the second pass. Increasing pH to greater than 10 in the second pass feed water can increase boron rejection from 65% to between 90% and 99% depending on the type of membranes used in each pass (Redondo et al., 2003; Gorenflo et al., 2007; Koseglu et al., 2008; Tomaszewska and Bodzek, 2013; Freger et al., 2015; Viatcheslav et al., 2015). An important consideration for systems that are conducting pH adjustment is the potential for scaling of the membranes which is highly dependent on the source water quality (Koseoglu et al., 2008).

Other water quality parameters such as temperature can influence the removal of boron and other dissolved parameters using RO, particularly during desalination (Guler et al., 2011). The primary considerations to ensuring adequate boron removal are the properties of the membrane, recovery, and operating pressure.

Limitations of the RO process include possible membrane scaling, fouling and failure, as well as higher energy use and capital costs. Calcium, barium and silica can cause scaling and decrease membrane efficiency. Since RO completely removes alkalinity in water, it will continually lower product water pH and increase its corrosivity. Therefore, the product water pH must be adjusted, and alkalinity may need to be increased to avoid corrosion issues in the distribution system such as the leaching of lead and copper (Schock and Lytle, 2011; U.S. EPA, 2012).

Ion exchange (IX)

IX is an effective treatment technology for the removal of boron. In general, removal of boron using a traditional strong base anion exchange resin is not efficient due to the presence of other anions such as bicarbonate, sulphate and chloride that compete for exchange sites with borate. In addition, strong base anion exchange is not effective unless the pH is above 9.2 (so that boron is present as borate ions) which is rarely applied for this process. As a result, BSRs have been developed (Kabay et al., 2010; Hilal et al., 2011; Wang et al., 2014; Yoshizuka and Nishihama, 2015; Kabay et al., 2018b). The most common BSRs are chelating IX resins synthesized by using macroporous crosslinked polystyrenic matrices that are functionalized with an N-methyl-D-glucamine (NMDG) group. The NMDG group forms a covalent attachment with boron which then forms an internal complex in the resin. This is also referred to as an adsorption process as it does not follow standard IX processes. The formation of these complexes does not require boric acid dissociation. Therefore, treatment can be effective over a wide pH range (Bodzek, 2015). A number of boron selective chelating resins are available commercially with theoretical boron capacities ranging from 0.6 to 1.2 eq/L. Details on the types and performance of various resins are discussed in greater detail by Hilal et al. (2011), Wang et al. (2014) and Kabay et al. (2018b).

The removal of boron by BSRs depends on several design/process parameters (type of resin, flow rate, height/depth ratio of resin) and water quality characteristics (influent boron concentration, temperature, pH). In theory, low treated water boron concentrations can be achieved using IX, particularly if resin regeneration is frequent, but this is often not operationally practical. Additionally, frequent regeneration has been shown to cause corrosion issues (that is, leaching of copper and lead) (Lowry, 2009, 2010) because ion exchange reduces alkalinity and causes the treated water pH to be lowered during short runs (Clifford, 1999; Wang et al., 2010).

Data reported in Table 5 provide an indication of the operational conditions that were used in several treatment plants to achieve removal efficiencies between 93% to 98% and treated water concentrations below 0.50 mg/L (Kabay et al., 2004; Jacob, 2007; Santander et al., 2013). The major limitation of IX using BSRs is regeneration and neutralization of the saturated resin as it requires a large volume of chemicals (acid and bases) that must be carefully handled. This is problematic in terms of not only the training required to operate these types of systems but also the high cost of regeneration chemicals (Wolska and Bryjak, 2013; Bodzek, 2015; Guan et al., 2016).

To reduce costs, system design often includes treating only a portion of the water for boron removal followed by blending with other water within the treatment plant. The characterization of the water quality must be carried out to ensure that changes in water quality resulting from blending are assessed and that potential impacts on the existing treatment processes and distribution system are determined.

Table 5. Studies on boron removal using boron selective IX
Source water Influent (mg/L) Effluent (mg/L) Process details Breakthrough (BV) Reference

Desalinated RO permeate


0.1 from IX

0.47 blended treated water concentration

Full-scale: treatment of 74% of RO permeate using IX followed by blending with 26% of untreated permeate

Resin: macroporous poly(styrene-co-DVB) with NMDG functional group

Resin diameter: 300-1 200 µm,

Flow rate: 30 BV/h


Jacob (2007)

Geothermal water


< DL

Small pilot-scale column study

Resin: macroporous poly(styrene-co-DVB) with NMDG functional group, diameter 300-1 200 µm

Flow rate: 15 BV/h


Kabay et al. (2004)

Geothermal water


0.3 mg/L (defined as breakthrough concentration)

Fixed bed column study

Resin: cellulose-based fibre containing NMDG functional group diameter 100 µm

Resin diameter: 100 µm

Flow rate: 15-30 BV/h

Column: diameter = 0.7 cm, 0.5 mL of fibre

225 (flow rate: 15 BV/h)

Recepoglu et al. (2018)

Geothermal water


0.5 mg/L (defined as breakthrough concentration)

Fixed bed column study

Resin: novel resin poly(N-(4-vinylbenzyl)-(N-methyl-D-glucamine), particle size 0.180-0.250 mm

Flow: 15 BV/h

Column: diameter = 0.7 cm, 0.5 mL of resin


Santander et al. (2013)

BV – bed volume; DL – detection limit; DVB – divinyl benzene; NMDG – N-methyl-D-glucamine; RO – reverse osmosis; IX – ion exchange

The effect of process parameters on boron removal using BRSs is summarized by Hilal et al. (2011), Bodzek et al. (2014), Yoshizuka and Nishihama (2015) and Ipek et al. (2016). The breakthrough point of a column is a critical parameter indicating the effectiveness of boron removal as it is directly connected to resin capacity. Studies have demonstrated that breakthrough column capacity decreases with higher flow rates due to reduced contact time between boron in solution and the resin (Kabay et al., 2008a; Yan et al., 2008). A greater height to diameter ratio can improve the breakthrough capacity as it increases the contact time and it enhances the liquid distribution in the column (Yan et al., 2008).

Residential scale

In cases where boron removal is desired at the household level, for example, when a household obtains its drinking water from a private well, a residential drinking water treatment unit may be an option for decreasing boron concentrations in drinking water. Before a treatment unit is installed, the water should be tested to determine the general water chemistry and boron concentration in the source water. To verify that a treatment unit is effective, water entering and leaving the treatment unit should be sampled periodically and submitted to an accredited laboratory for analysis. Units can lose removal capacity through use and time and need to be maintained and/or replaced. Consumers should verify the expected longevity of the components in the treatment unit according to the manufacturer's recommendations and service it when required.

Health Canada does not recommend specific brands of drinking water treatment units, but it strongly recommends that consumers use units that have been certified by an accredited certification body as meeting the appropriate NSF International Standard/American National Standard (NSF/ANSI) for drinking water treatment units. The purpose of these standards is to establish minimum requirements for the materials, design and construction of drinking water treatment units. This ensures that materials in the unit do not leach contaminants into the drinking water (that is, material safety). In addition, the standards include performance requirements that specify the removal that must be achieved for specific contaminants (that is, reduction claim) that may be present in water. Certification organizations provide assurance that a product conforms to applicable standards and must be accredited by the Standards Council of Canada (SCC). Accredited organizations in Canada (SCC, 2022) include the following:

An up-to-date list of accredited certification organizations can be obtained from the SCC.

The drinking water treatment units that are expected to be effective for boron removal at the residential scale include (NGWA, 2018):

The effectiveness of RO units for boron removal is dependent on the membrane (filter) type and pH of the water and anticipated removals range from 50% to 90% (based on municipal-scale data). Therefore, an RO system will need to be carefully selected to achieve treated water concentrations below the MAC. In addition, it may be necessary to pre-treat the water to reduce fouling and extend the service life of the RO membrane. Although there is a lack of data regarding the use of distillation for removal of boron from drinking water, it is expected to adequately remove boron, because it is effective for the reduction of other inorganic contaminants. However, this process requires a high electrical energy input. Consumers may want to consult a water treatment professional for advice on available treatment systems, as well as installation and maintenance costs, based on their specific water quality.

Water that has been treated using RO and distillation may be corrosive to internal plumbing components. Also, as large quantities of influent water are needed to obtain the required volume of treated water, these devices are generally not practical for point-of-entry installation. Therefore, these units should be installed only at the point-of-use.

Although IX is an effective treatment technology for boron removal for municipal-scale systems, it requires the use of a specific type of resin that needs to be regenerated using a large volume of acid. Since this is a complex process that requires extreme care, this type of treatment is not practical at the residential scale. Currently, boron is not included in the performance requirements (for example, reduction claims) of NSF/ANSI standards. However, use of a treatment unit that is certified to the standards for RO or distillation will ensure that the material safety of the units has been tested. These standards are NSF/ANSI Standard 58 (Reverse Osmosis Drinking Water Treatment Systems) and NSF/ANSI Standard 62 Drinking Water Distillation Systems (NSF/ANSI, 2021a, b).

Summary of treatment achievability

Data from full- and pilot-scale treatment plants indicate that when concentrations of boron are below 8 mg/L in source water, treated water concentrations well below 5 mg/L are achievable using SWRO or IX treatment technologies with varying complexity and operating conditions. However, existing full-scale RO systems that are not specifically designed for boron removal may require modifications or additional resources to achieve boron concentrations below 5 mg/L. Achieving a treated water concentration of 5 mg/L gives drinking water treatment providers flexibility in selecting the treatment technology that is best suited for their water quality, existing treatment processes, and available technical and financial resources. Larger municipal systems that can operate more complex treatment systems, such as multi-pass RO or combinations of treatment technologies, may be capable of achieving treated water concentrations of less than 0.5 mg/L (Hilal et al., 2011).

It is anticipated that elevated boron concentrations may impact some smaller groundwater systems in Canada. For small systems with limited resources, it is important that the treatment system not be overly complex to install and operate. Single-pass RO is the simplest treatment system for boron removal. Data indicate that achieving a treated water concentration of 5 mg/L or less is practical for this type of treatment technology (boron rejection between 65% and 85%).

Generally, it is recommended that residential-scale treatment units be certified to meet the NSF International (NSF)/American National Standards Institute (ANSI) standards. Currently, a reduction claim for boron is not included in these standards. However, point-of-use reverse osmosis treatment units are likely the most applicable at the residential scale. RO units that comprise a single membrane element are expected to achieve greater removal (for example, > 75%) than municipal-scale systems. Treated water concentrations below 5 mg/L could be achieved even when maximum source water concentrations are as high as 8 mg/L.

Distribution system considerations

Although significant research has been conducted in recent years on the potential accumulation and release of contaminants in drinking water distribution systems (Friedman et al., 2010, 2016), no information was found in the literature regarding the presence of boron in distribution system scales. However, given that boron has been shown to adsorb onto aluminium and iron oxides in the environment (see Environmental fate), it is possible that boron may accumulate within distribution systems where these types of deposits are present.

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