granular activated carbon testing

Photo image area measures 2” H x 6.93” W and can be masked by a collage strip of one, two or three images.

The photo image area is located 3.19” from left and 3.81” from top of page.

Each image used in collage should be reduced or cropped to a maximum of 2” high, stroked with a 1.5 pt white frame and positioned edge-to-edge with accompanying images.

Granular Activated Carbon TestingJonathan G. Pressman

Office of Research and DevelopmentNational Risk Management Research Lab 9/26/19

Presenter

Presentation Notes

Understanding issues related to low disinfection residuals

Contributors

Gulizhaer Abulikemu Thomas Speth Jeff Vogt Maria Mayer Ying Hong Thomas (Mac) Kelley Gulizhaer Abulikemu Toby Sanan Tim Neyer Dionysios Dionysiou Paul Rossman Stephanie Brown David Griffith Deborah Roose Clermont County Ohio Water Resources Department Greater Cincinnati Water Works

Outline

Introduction/GAC 101

Case Studies:Pilot Scale - PFAS

Bench Scale - cVOCs

Bench Scale - Microcystin-LR

Bench Scale - Standardization of NOM

Adsorption and GAC

Adsorption is the accumulation of material at the interface between two phases

Activated carbon is the most common adsorbent because it can economically adsorb a broad spectrum of organic chemicals, a result of its extremely large surface area

https://pacificwater.com.au

https://pacificwater.com.au/

Factors Affecting Adsorption

Adsorbate Solubility Polarity MW Charge Concentration

Activated CarbonSolution Conditions

Temperature pH

Binding forces Physical Chemical Specific

Adsorption Equilibrium

In the presence of GAC, chemicals in water will partition between the carbon and water, such that a chemical equilibrium between the two phases is eventually established

Freundlich isotherm – qe=KCe1/n

K = adsorption capacity at unit concentration (mg/g)(L/mg)1/n

1/n = adsorption intensity (dimensionless)

Log

q e(m

g/g)

Log qe = Log K + 1/n LogCe

Log Ce (mg/L)

Kinetics

Transport from bulk liquid to liquid film Transport across liquid film to GAC surface Transport within GAC particle by surface and pore diffusion Adsorption to the GAC surface

Controlling factors GAC diameter GAC type Chemical being adsorbed Chemical concentrationWater quality Competition

Need for Testing

Full-scale

Pilot-scale

Bench-scale

Presenter

Presentation Notes

RSSCT – three primary advantages Fraction of the time of pilot studies Unlike predictive mathematical models, extensive isotherm or kinetic studies are not required to obtain a full scale performance prediction from an RSSCT Only a small volume of water is required

Bench Scale

Rapid Small Scale Column Tests (RSSCTs) A benefit because:

Shorter Duration Small volume of water Data can be scaled up to performance of Full Scale unit Mathematical relationships used to scale

Based on mathematical similitude – dimensionless parameters equal for both systems

Surface/pore diffusion modulus, solute distribution parameter, Stanton number, Reynolds number, etc.

Two primary test design scenarios:

Constant Diffusivity: 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝑆𝑆𝑆𝑆𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐿𝐿𝑆𝑆

= 𝑅𝑅𝑆𝑆𝑆𝑆𝑅𝑅𝐿𝐿𝑆𝑆

2= 𝑡𝑡𝑆𝑆𝑆𝑆

𝑡𝑡𝐿𝐿𝑆𝑆

Proportional Diffusivity: 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝑆𝑆𝑆𝑆𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐿𝐿𝑆𝑆

= 𝑅𝑅𝑆𝑆𝑆𝑆𝑅𝑅𝐿𝐿𝑆𝑆

= 𝑡𝑡𝑆𝑆𝑆𝑆𝑡𝑡𝐿𝐿𝑆𝑆

Presenter

Presentation Notes

Constant diffusivity – when the surface diffusivity of the chemical on the carbon is the same for the Large and Small scale. Proportional diffusivity – when the surface diffusivity of the chemical on the on carbon is proportional to the partical size of the carbon. This has been found over the years for larger molecules such as NOM and large MW synthetic organic chemicals. Longer run time and EBCT are required because the particle size ratio is only raised to the first power.

Modeling

Pore and Surface Diffusion Model (PSDM)

AdDesignS

WBS cost models

https://www.epa.gov/dwregdev/drinking-water-treatment-technology-unit-cost-models-and-overview-technologies

Presenter

Presentation Notes

Python Enables automated fitting of pilot data to model results Vary K and 1/n for each Carbon/chemical combination Select the pair that minimizes sum-of-squared difference Predictions then allow for design evaluations Work breakdown structure models A treatment technology is broken down into discrete components that can be measured for the purpose of estimating costs. The components include specific equipment (e.g., tanks, vessels, pipes, and instruments) and other identifiable cost elements such as annual expenditures on labor, chemicals, and energy. There are 37 different cost models – some for main treatment processes and others for add-on pre- and post-treatment processes. Most of the models exist in draft form and several of the main treatment process models have undergone peer review. Multi-state bubble aeration, packed tower aeration, and GAC models have been uploaded to EPA’s website. The anion exchange, biological treatment, and non-treatment models are finished and are waiting to be uploaded. Here is the link. You can find it by Googling EPA WBS.

https://www.epa.gov/dwregdev/drinking-water-treatment-technology-unit-cost-models-and-overview-technologies

Case Study – Pilot Scale PFAS

Objectives

Evaluate GAC for the removal of PFASs at lower concentrations in the submicrogram per liter range, not currently regulated.

Evaluate adsorptive competition on the GAC between the PFAS and NOM, which could become highly relevant at the low PFAS concentrations of interest.

Calculate carbon usage rates (CUR) for the GAC and PFAS of interest.

Presenter

Presentation Notes

Longer operation improves knowledge about performance Pilot sees more variability in water quality Improves knowledge about impact of fouling/competitive adsorption Uses unmodified carbons


Pilot Configuration4 in diameter4 ft length0.25 gpm (results in 10-min EBCT)~10 lbs of carbon2 columns in series = 2x EBCT trialExpected duration 4-6 months<30 ppt individual PFASs Partial breakthrough beginning after ~1

monthComplete breakthrough 2+ months


0.00

0.50

1.00

1.50

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000

C/C0

Bed Volumes

PFBA (C4) PFPeA (C5) PFHxA (C6) PFHpA (C7)

PFOA (C8) PFNA (C9) PFDA (C10) PFBS (C4)

PFPeS (C5) PFHxS (C6) PFHpS (C7) PFOS (C8)

PFMOAA* PFO2HxA* PFO3OA* PFPrOPrA/GenX

PFO4DA* Nafion BP2*

10-min EBCT

Modelingcourtesy Jonathan Burkhardt

Modeling helps extend the usefulness of Pilot/RSSCT data

Test impact of different influent conditions, bed sizes or flowrates

Compare difference between GACs

Fit Pilot Data

Model

Con

cent

ratio

n (n

g/L)

Predict Full-Scale w/ Multiple PFAS

Total

Days

Tota

l Con

cent

ratio

n (n

g/L)

Model Different Operational Conditions

Current Flow, average conc.Current Flow, lower conc.Current Flow, higher conc.Future Flow, average conc.Future Flow, lower conc.Future Flow, higher conc.

Expected Bed Replacement Frequency (Days)

Case Study: cVOCs

Objectives

Evaluate GAC for the removal of a group of cVOCs at lower concentrations in the submicrogram per liter range, including additional cVOCs not currently regulated.

Evaluate adsorptive competition on the GAC between the cVOCs and DOM, which could become highly relevant at the low cVOCconcentrations of interest.

Calculate carbon usage rates (CUR) for the GAC and cVOCs of interest.

Presenter

Presentation Notes

Former USEPA Administrator Jackson introduced a drinking water strategy to expand public health protection by going beyond the traditional framework that regulates one contaminant at a time. Specifically, one of the strategies is to accelerate advancement of drinking water protection by addressing contaminants as a group rather than one at a time. Additionally, with a maximum contaminant level (MCL) goal of zero for the regulated carcinogenic volatile organic compounds (cVOCs), recently improved analytics may allow for lower MCL determinations under Six Year review. These two drivers have led to interest in writing a group regulation for cVOCs. To regulate cVOCs at lower concentrations, the USEPA must know if the designated Best Available Technology (BAT) will work cost-effectively at these concentrations. The BATs for the currently regulated cVOCs are granular activated carbon (GAC) and packed tower aeration (PTA). The current research is designed to evaluate GAC adsorption as a BAT for cVOCs at sub-microgram per liter concentrations. Using the CURs developed in this research, the USEPA Office of Water can calculate the costs associated with a potential group cVOC regulatory action and determine if GAC remains a BAT at the lower concentrations of interest

Experimental Apparatus

cVOC Breakthrough

GAC Fouling

NOM Effects

Carbon Usage Rates

Case Study: Microcystin-LR

Objectives

Use RSSCTs to assess the effectiveness of GAC in treating cyanotoxins, particularly MC-LR

Investigate competitive adsorption/interactions of NOM (TOC) and MC-LR

Use RSSCTs to evaluate the adsorption capacity of GAC in treating cyanotoxins when the GAC was preloaded with NOM at different levels

RSSCT Apparatus & Design

• EBCTSC = 0.84 min

• EBCT LC = 10 min

• Hydraulic loading rate (v)= 1.73 m h-1

• Flow Rate= 0.32 mL/min

• Sieve size= 100 × 200

• RSSCT column diameter= 3.74 mm

• Bed Volume= 0.27 mL

• Bed Length= 2.42 cm

• dp LC = 1.29 mm

• dp SC = 0.11 mm

• SF= 11.8

Feed Water and GAC

Feed water, i.e., GAC Influent water (GACI) was collected from the drinking water utility

GAC was also collected from the utility Regenerated with 15% virgin makeup

GAC was ground to meet 0.11 mm average particle size (100 x 200 sieve size)

GAC rinsed to separate “fines” to prevent pressure buildup in column

Varying NOM PreloadingM

C-L

R (µ

g L

-1)

0

2

4

6

8

10

Influent A

Influent C

Influent BEffluent A (0%)

Effluent C (100%)

Effluent B (55%)

0 40000 60000 80000Bed Volumes6min EBCT, 80% at 30000 BV

(Hall et al.2000)

20000

Case Study: Standardized NOM

Objectives

Evaluate water quality conditions of reconstituted GAC influent water (Recon GACI) that are essential for conducting RSSCT studies that compare with original GAC influent water (GACI) RSSCTs.

Compare RSSCT predicted breakthrough behaviors of NOM in GACI and Recon GACI, to evaluate if Recon GACI can be used as a surrogate for source water.

Compare the RSSCT predicted NOM breakthrough profiles obtained using virgin and regenerated GACs to the full-scale breakthrough profile.

RSSCT Apparatus & Design

Pressure Gauge

3-way Valves

Influent Carboy

Glass Wool

Automatic fraction collector

Pulse Dampener

GAC

Pump

Major RSSCT design parameters include :1. GAC mesh size: 230 × 325 2. Column internal diameter: 0.38 cm3. GAC bed height: 4.1 cm4. Empty bed contact time (EBCT):

0.81min5. Flow rate: 0.58 ml/minOther RSSCT design and operation parameters are specified elsewhere (Zhi Weili et al. 2012 ).

GAC Preparation

Grind GAC with mortar and pestle, collect particles between sieves 230 and 325 mesh size (54 µm).

Rinse collected particles with milli-Q water multiple time to remove fines.

Dry at 95 ℃ .

NOM ComparisonTO

C m

g/L

0.5

1

1.5

2

2.5

00 5000 10000 15000 20000 25000

Throughput (Bed Volumes)

GACI Influent

GACI Effluent

Recon GACI Influent

Recon GACI Effluent

RSSCT vs. Full ScaleN

orm

aliz

ed T

OC

, C/C

0

00.10.20.30.40.50.60.70.80.9

1

0 50 100 150 200 250

Large column days

Virgin RSSCT_GACI

Virgin RSSCT_Recon GACI

Regenerated RSSCT_GACI

Regenerated RSSCT_Recon GACI

Full scale

Photo image area measures 2” H x 6.93” W and can be masked by a collage strip of one, two or three images.

The photo image area is located 3.19” from left and 3.81” from top of page.

Each image used in collage should be reduced or cropped to a maximum of 2” high, stroked with a 1.5 pt white frame and positioned edge-to-edge with accompanying images.

Questions? Jonathan G. [email protected]

DisclaimerThe information in this presentation has been reviewed and approved for public dissemination in accordance with U.S. Environmental Protection Agency (EPA) policy. The views expressed in this presentation are those of the author(s) and do not necessarily represent the views or policies of the EPA. Any mention of trade names or commercial products does not constitute EPA endorsement or recommendation for use.

Office of Research and DevelopmentNational Risk Management Research Lab 9/26/19

mailto:[email protected]

granular activated carbon testing

Documents