Anion Exchange Resin and Inorganic Anion Parameter Determination for Model Validation and Evaluation of Unintended Consequences during PFAS Treatment

Smith, Samantha J.; Wahman, David G.; Kleiner, Eric J.; Abulikemu, Gulizhaer; Stebel, Eva K.; Gray, Brooke N.; Datsov, Boris; Crone, Brian C.; Taylor, Rose D.; Womack, Erika D.; Gastaldo, Cameron X.; Sorial, George A.; Lytle, Darren A.; Pressman, Jonathan G.; Haupert, Levi M.

doi:10.1021/acsestwater.2c00572

Cited by 7 publications

(13 citation statements)

References 46 publications

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“…The tributyl groups significantly enhance the nitrate selectivity compared to typical strong base anion exchange resins (details in Table S3). ,, All materials are commercially available, but no endorsement is implied.…”

Section: Methodsmentioning

confidence: 99%

Resilient Nitrate Removal by a Biological Nitrate-Selective Ion Exchange (BIO-NIX) Process

Dong,

Chen,

Shepsko

et al. 2023

ACS EST Water

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Nitrate violation is increasing globally due to substantial fertilization to feed the growing population. Biological denitrification (BIO) represents one of the major techniques in addressing nitrate contamination, but it lacks resiliency in handling system fluctuations. To improve the resiliency, we have demonstrated a biological nitrate-selective ion exchange (BIO-NIX) process for resilient nitrate removal, which differentiates from typical biologically regenerated ion exchange that requires intermittent interruption of regeneration. BIO-NIX combines a fixed-bed BIO column and a nitrate-selective ion exchange (NIX) column. Efficient denitrification (over 90%) was enabled by biofilms attached to a highly porous ceramic host material in the BIO column, and the effluent was polished by the NIX column to handle system fluctuations. To enable efficient denitrification, we designed a self-adjusted carbon-releasing system using a citrateloaded ion exchange column. The whole system operated for over two months under conditions of carbon shortage, influent nitrate surge, and flow rate jump; resilient nitrate removal to below 45 mg/L (MCL as NO 3 − ) was achieved without intermittent regeneration of the nitrate-selective resin. The BIO-NIX system is also retrofittable to a biologically regenerated NIX process (BIO-RNIX) to fully restore resin capacity if necessary. The demonstrated resiliency enables BIO-NIX to be deployed in various applications, especially in decentralized, rural areas.

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Section: Methodsmentioning

confidence: 99%

Resilient Nitrate Removal by a Biological Nitrate-Selective Ion Exchange (BIO-NIX) Process

Dong,

Chen,

Shepsko

et al. 2023

ACS EST Water

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“…A complete specification of the ion exchange column model (referred to here as HSDMIX) can be found in Smith et al (2023). The model is implemented as an open‐source code library and is freely available on GitHub (USEPA, 2023b).…”

Section: Methodsmentioning

confidence: 99%

“…Neglecting chemical activity adjustments, the ion exchange isotherm between a hypothetical ion (

B

) and another ion (

A

) can be approximated by the apparent equilibrium coefficient (Helfferich, 1995; Zagorodni, 2006), given in terms of liquid‐phase concentration (

C

), resin‐phase concentration (

q

) and valence (

Z

) (Equation ). The selectivity values (Equation ) of major counterions against chloride were previously determined to be 0.033 for sulfate, 0.31 for bicarbonate, and 13 for nitrate (Smith et al, 2023).

K_{B, A} goodbreak= {(\frac{q_{B}}{C_{B}})}^{Z_{A}} {(\frac{C_{A}}{q_{A}})}^{Z_{B}} .

…”

Section: Methodsmentioning

confidence: 99%

“…In an ideal ion exchange column (one with no chromatographic effects or sorption front dispersion), the number of bed volumes that can be treated (

normalΓ

) for a given contaminant (

i

) can be expressed in terms of the bed porosity (

ε

), the influent concentration, and the equilibrium resin‐phase concentration. The porosity (

ε

) of the packed bed was assumed to be 0.37 (Smith et al, 2023). Note that in this work

normalΓ

is dimensionless, and

q

is defined as the contaminant concentration inside the resin beads (meq/L).…”

Section: Methodsmentioning

confidence: 99%

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Impact of phosphate addition on PFAS treatment performance for drinking water

Haupert,

Redding,

Gray

et al. 2023

AWWA Water Science

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Adding new unit operations to drinking water treatment systems requires consideration of not only efficacy for its design purpose but also costs, water quality characteristics, impact on overall regulatory compliance, and impact of other treatment unit operations. Here, pilot study results for ion exchange (IX) and granular activated carbon (GAC) are presented for a utility with both per‐ and polyfluoroalkyl substances (PFAS) and volatile organic contaminant removal needs. Specifically, the impact of upstream air stripping and phosphate addition on PFAS treatment performance was evaluated. Modeling was used to fit the IX and GAC pilot data and predict performance under different scenarios. GAC performance was generally consistent for treating water before or after the air stripper, but the addition of phosphate prior to air‐stripping resulted in a loss of 15%–25% capacity for some PFAS on IX media, demonstrating the need to consider the entire treatment train before implementing PFAS removal unit operations.

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“…Recently, Smith et al 30 addressed some noted data gaps for inorganic anions, determining nitrite, sulfate, and bicarbonate selectivity with respect to chloride (K N/C , K S/C , and K B/C , respectively) for three strong base anion exchange resins (studied herein) recommended for PFAS removal and then validating a developed and publicly available ion exchange column model (https://github.com/USEPA/Water_ Treatment_Models). Considering remaining research needs, the objective of the current work was an extension of Smith et al 30 to PFAS, estimating K PFAS/C to support future PFAS column studies and ion exchange column model expansion and validation. Using three strong base anion exchange resins, K PFAS/C was estimated for nine PFAS (Table 1) at relevant drinking water equilibrium PFAS liquid concentrations (≤500 ng/L).…”

Section: ■ Introductionmentioning

confidence: 99%

Strong Base Anion Exchange Selectivity of Nine Perfluoroalkyl Chemicals Relevant to Drinking Water

Wahman,

Smith,

Kleiner

et al. 2023

ACS EST Water

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Selectivity with respect to chloride (K PFAS/C) was determined for nine drinking water relevant perfluoroalkyl and polyfluoroalkyl substances (PFAS): perfluoro-2-propoxypropanoic acid (GenX), five perfluoroalkyl carboxylic acids (PFCAs), and three perfluoroalkyl sulfonic acids (PFSAs). Three single-use strong base anion exchange gel resins were investigated, targeting drinking water relevant equilibrium PFAS liquid concentrations (≤500 ng/L). Except for the longest carbon chain PFCA (perfluorodecanoic acid) and PFSA (perfluorooctanesulfonic acid) studied, PFAS followed traditional ion exchange theory (law of mass action), including increasing equilibrium PFAS liquid concentrations with increasing equilibrium chloride liquid concentrations. Overall, K PFAS/C values were (i) similar among resins for a given PFAS, (ii) 1–5 orders of magnitude greater than the selectivity of inorganic anions (e.g., nitrate) previously studied, (iii) 2 orders of magnitude greater for the same carbon chain length PFSA versus PFCA, (iv) found to proportionally increase with carbon chain length for both PFSAs and PFCAs, and (v) similar for GenX and perfluorohexanoic acid (six-carbon PFCA). A multisolute competition experiment demonstrated binary isotherm-determined K PFAS/C values could be applied to simulate a multisolute system, extending work previously done with only inorganic anions to PFAS. Ultimately, estimated K PFAS/C values allow future extension and validation of an open-source anion exchange column model to PFAS.

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Anion Exchange Resin and Inorganic Anion Parameter Determination for Model Validation and Evaluation of Unintended Consequences during PFAS Treatment

Cited by 7 publications

References 46 publications

Resilient Nitrate Removal by a Biological Nitrate-Selective Ion Exchange (BIO-NIX) Process

Resilient Nitrate Removal by a Biological Nitrate-Selective Ion Exchange (BIO-NIX) Process

Impact of phosphate addition on PFAS treatment performance for drinking water

Strong Base Anion Exchange Selectivity of Nine Perfluoroalkyl Chemicals Relevant to Drinking Water

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