Powdered and Granular Activated Carbon Treatment for TOC Reduction and Stage 2 D/DBPR Compliance

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Roger Tucker
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1 Powdered and Granular Treatment for TOC Reduction and Stage 2 D/DBPR Compliance NC AWWA-WEA Spring Conference, Wilmington, NC April 15, 2013 Pete D Adamo, PhD, PE pdadamo@hdrinc.com

2 Basics Learning Objectives and Outline Ø Total Organic (TOC) Basics Ø Basics Ø to Evaluate Ø with Ø Types of Delivery Ø Summary and Conclusions

3 Basics Natural Organic Matter

4 Basics Natural Organic Matter

5 Basics Why Are We Concerned About NOM/TOC? Ø Organic Compounds Represent Sources of Tastes, Odors and Color Ø Precursor for Disinfection By-Products Ø Potential Health Concerns Ø Many Organics are EDCs, PPCPs and CECs and may be Subject to Future Regulation Ø Potential Source for Biological Regrowth in Distribution Ø Regulatory Compliance Stage 1 and 2 D/DBPR

6 Basics DBP Control = Controlling this Equation Chemical Disinfectant Precursor + DBPs = Chlorine Monochloramine Ozone Chlorine Dioxide + Natural Organic Matter Bromide = Trihalomethanes Haloacetic Acids Haloacetonitriles Haloketones Aldehydes Bromate and many more

7 Basics What is? Ø A highly porous charcoal that effectively removes organic compounds from air and water Ø Available as a powdered (PAC) or granular (GAC) material

8 Basics GAC vs. PAC Ø Granular (GAC) Particle size: larger than 0.1 mm Typical range 0.4 to 2.5 mm Bulk dry (apparent) density 0.22 to 0.5 kg/l Used in adsorption columns/filters Ø Powdered (PAC) Particle size: < 200 mesh (74 µm) Typical range µm Bulk dry (apparent) density 0.34 to 0.74 kg/l Used by direct addition

9 Basics Where Does it Come From? Ø Produced from a variety of source materials Coal Wood Coconut shells Ø Raw materials are heated (in two stages) to form activated carbon

10 Basics Manufacturing Courtesy of Calgon Corporation

11 Basics Internal Surface Area Courtesy of Calgon Corporation

12 Basics Diffusion in Particle

13 Basics Breakthrough Bed Life Conc. Influent Effluent Saturation Time Finished water TOC goal will determine what breakthrough percent is allowed and when carbon change-out will occur.

14 Basics for Assessing with Ø Isotherm - GAC Ø Jar - PAC Ø Rapid Small Scale Column - GAC Ø Pilot Column - GAC

15 Basics GAC Adsorption Isotherm Where q = (TOC initial TOC final )/ Dose (g/l) Norit HD3000 and Calgon Filtersorb 300

16 Basics PAC Jar Evaluate the performance of different PACs Determine optimum dose Evaluate mixing energy and time Evaluate impact on coagulation chemistry Obtain Raw Water for Conduct Jar with Plant Specific Conditions Analyze for TOC at Different Doses Calculate and Select PAC Type/ Dose

17 Basics Pilot Column Ø Advantages: Incorporates fluctuations in influent quality and flow rate Large enough to backwash and consider physical throughput Ø Disadvantages Time consuming Expensive

18 Basics Mini-column Accelerated Column (ACT) (Calgon) Rapid Scale Small Column Test (RSSCT) (Michigan State) Pulverize to reduce particle size and increase rate Apply scale up factors (for reduced particle size and accelerated flow)

19 Basics and DBP Reduction with Strategy/Technology Enhanced Coagulation/Alternate Coagulants Chlorine Dioxide Pre-treatment TOC/DBP Reduction Potential 0 to 10% 0% TOC, 10 to 50% DBPs PAC Pretreatment 5 to 25% MIEX 50 to 70% Ozone / Biological Active Filtration 0 to 20% Post Filtration GAC Contactors 25 to 75%

20 Basics Powdered Townsend WTP Raw Water TOC/DOC Ferric Dose Caustic Dose Raw Water Temperature 3.81 mg/l/3.75 mg/l 40 mg/l 4 mg/l 25 o C Raw Water ph 7.1 ~ 22% at 30 mg/l PAC CFE FW

21 Basics PAC Addition Concord, NC Hillgrove WTP 7-Day TTHM Formation Potential 67 mg/l per mg/l TOC 7-Day HAA5 Formation Potential 45 mg/l per mg/l TOC ~ 14% DBP 15 mg/l PAC Up to ~ 22% at 25 mg/l PAC

22 Basics RSSCT Results - GUC Filtersorb x 200 mesh fraction EBCT 1.26/15 minutes Temperature C ph 6.3 Initial TOC 4 mg/l UV cm -1 Flow 2 ml/min THMFP, ug/l THMFP Logistic Function Fit MCL 80% MCL Full- scale service time, days

23 Basics Post-Filter GAC Contactors Rapid Mix Floc/Sed Dual-Media Filter Storage Distribution GAC Contactor

24 TOC Basics Basics Typical GAC Arrangement Post-Filter Contactor 2 8 gpm/sf EBCT of 7-25 minutes per vessel Typically 10 to 12 in diameter; 18 to 22 tall Typical carbon loading - 4 to 8 feet, 20,000 lbs Granular Media Filter Adsorber 2 6 gpm/sf EBCT of 5-20 minutes Typical media depth 3 to 6 feet

25 Basics Dry PAC Delivery Options 40 to 45 lbs/33 bags/pallet 30,000 to 32,000 lb load 750 lb bulk bags

26 Basics Delivery PAC Feeders Bag Loading Bulk Bag

27 Basics PAC Bulk Silo Feed

28 Basics PAC Slurry System Mixer Slurry (1-2lbs/gal) Feed Pump

29 Basics Typical - PAC Ø PAC - $0.50 to $1.00 per pound Dose (mg/l) 1 MGD 5 MGD 10 MGD 20 MGD 5 $10,654 $53,272 $106,544 $213, $21,309 $106,544 $213,087 $426, $31,963 $159,815 $319,631 $639, $42,617 $213,087 $426,174 $852,348 Based on $0.70/lb Ø Equipment Cost - $200K to $500K

30 Basics Typical - GAC Ø Capital Cost - $0.25 to $0.50 per gallon Ø GAC Media - $1.50 per pound regenerated Ø 10 MGD WTP ~ $230,000 per change out 4 gpm/sf 1,750 SF filter area, 3 foot GAC depth GAC density - 30,000 lbs/cf

31 Basics Summary and Conclusions Ø PAC and GAC are effective technologies for reducing TOC concentrations, minimizing DBPs and can remove selected contaminants of concern Ø Both technologies are costly to operate Ø Before considering the use of PAC, bench scale testing should be conducted to determine effectiveness and cost Ø Bench and/or pilot scale testing are required for GAC including monitoring TOC removal and DBP formation potential

32 Basics Specificity

Enhanced Organic Precursor Removals Using Aged Filter Media Page 1. Enhanced Organic Precursor Removals Using Aged Filter Media

Enhanced Organic Precursor Removals Using Aged Media Page 1 Enhanced Organic Precursor Removals Using Aged Media O b j e c t i v e s The main goals of this project was to evaluate the dissolved organic