Taste and Odor Mitigation Strategies Laboratory-Based Analysis

Transcription

1 Taste and Odor Mitigation Strategies Laboratory-Based Analysis 2013 PNWS-AWWA Conference Spokane, WA Kim Ervin, P.E., West Region Drinking Water Service Lead, CH2M HILL

2 Outline Introduction - Sources of Taste and Odor Treatment Effectiveness DAF with Ozone Biological Filtration Powdered Activated Carbon (PAC) and Superfine PAC Oxidants and Advanced Oxidation Comparing the Results

3 INTRODUCTION

4 Significance of Taste and Odor Occurrence Survey of 800 utilities in the U.S and Canada showed: 16% experience taste and odor (T&O) problems 4.5% of their total budget is spent on T&O control Survey of 100 utilities by Summers et al. found: 15% experience problems for more than 4 months of the year Raw water concentrations as high as 1,700 and 240 ng/l were reported

5 Responses Types of Odor Problems Experienced by U.S. Utilities (Suffet, 1993) Chlorinous Earthy Fishy Medicinal Chemical Grassy Swampy Sulfide Petroleum Septic Other

6 CONTROL AND TREATMENT LABORATORY-BASED ANALYSIS

7 CONTROL AND TREATMENT DISSOLVED AIR FLOATATION (DAF) AND OZONE

8 Winnipeg High-Rate DAF Pilot Test One of the first high-rate DAF evaluations for a large (105 mgd) WTP Extensive piloting of both conventional and highrate DAF reduced construction costs DAF cost model allowed comparison of overall costs for different systems Pre-negotiated DAF equipment bid process to shorten the construction schedule

9 TON Winnipeg Pilot Results - DAF & Ozone Apr- 15- Apr- 29- Apr- 12- May- 27- May- 10- Jun- 23- Jun- 7- Jul- 22- Jul- 13- Aug- 26- Aug- 2- Sep- 23- Sep- Raw Post DAF Post O3

10 CONTROL AND TREATMENT BIOLOGICAL FILTRATION

11 What is Biological Filtration? Conventional Filtration Common points of chlorine application Raw Water Rapid Mix Flocculation Sedimentation Filtration

12 What is Biological Filtration? Biological Filtration No chlorine upstream of filters Raw Water Rapid Mix Flocculation Sedimentation Filtration Filter media supports biomass

13 What s the Difference Between BAC Filtration and GAC Adsorption? GAC adsorption requires regular replacement of GAC (depends on water quality, but could be 1x/yr or more) In filters, GAC typically has less empty bed contact time (EBCT), resulting in even more frequent replacement of GAC Post-filter GAC contactors expensive, but provide longer EBCT and less frequent GAC replacement versus GAC adsorption in filters With BAC filters, GAC replacement frequency extends to 5-10 years or more, resulting in reduced O&M costs BAC provides less removal of TOC and micro-constituents BAC is still an important barrier in a robust, multi-barrier water treatment train

14 Acclimation Experiment Objectives To investigate the impact of: Time on acclimation to MIB and geosmin Empty bed contact time (EBCT)

15 Low Ozone Low Ozone MIB/Geosmin Feed MIB (ng/l): 0 Geosmin (ng/l): 0 Tank 1 Tank 2 Feed MIB (ng/l): 24 Geosmin (ng/l): 21 Sand Sand Low Temp BAC Sand GAC Sand Sand Low BAC Sand Temp Backwash Tank To Waste To Waste

16 Removal Percentage Impact of Acclimation Time on Sand Biofilter Performance 90% 80% 70% MIB EBCT = 13 min GSM EBCT = 13 min 60% 50% 40% 30% 20% 10% Significant time was required for acclimation to MIB and Geosmin. 0% 8-Jun 28-Jun 18-Jul 7-Aug 27-Aug 16-Sep 6-Oct 26-Oct 2003

17 Percent Removal (%) Impact of Empty Bed Contact Time Empty Bed Contact Time (min) MIB Geosmin Note: Initial concentration of MIB and geosmin were 20 ng/l each.

18 Steady-State Experiment Objectives To investigate the impact of the following on biofilter performance: Preacclimation to MIB and geosmin Media type Temperature Empty bed contact time (EBCT) Influent concentration

19 Low Ozone Low Ozone MIB/Geosmin Feed MIB (ng/l): 20, 98 Geosmin (ng/l): 11, 98 Tank 1 Tank 2 Feed MIB (ng/l): 23, 88 Geosmin (ng/l): 17, 82 Sand Sand Low Temp BAC Sand GAC Sand Sand Low BAC Sand Temp Backwash Tank To Waste To Waste

20 Biomass nmol PO 4 /g dry media Steady-State Biomass Concentrations Top Middle Preacclimated BAC Low Temp Sand Sand Sand Filter

21 Percent Removed (%) Steady-State Biofilter Performance Preacclimated to MIB and Geosmin Sand (20) Sand (80) BAC (20) Unacclimated to MIB and Geosmin BAC (80) Sand Low Temp (20) Sand Low Temp (80) MIB Geosmin Sand (20) Sand (80)

22 Biological Filtration Summary Preacclimation to MIB and geosmin was critical for biofilter performance on sand media in pilot scale experiments. BAC sustained higher concentrations of biomass and showed increased removals of MIB and geosmin. The lower temperature column showed lower removals of MIB and geosmin. Longer EBCTs may be required for adequate removal of MIB and geosmin. A reacclimation to higher influent concentrations was observed.

23 CONTROL AND TREATMENT POWDERED ACTIVATED CARBON (PAC)

24 Powdered Activated Carbon Contact Time Application (or Dosing) Point Adsorption capacity, Brand and Type of PAC Interferences: natural organic matter (NOM), coagulants (such as alum), chlorine Chlorine consumption

25 Concentration, ng/l Compared Two PACs for T&O Control (Spiked #1 - Reservoir Water) Task 2.2A: PAC Pretest - Reservoir Water Mixing = 10 minutes at 50 rpm Note: Numbers next to PAC type in legend are doses in mg/l Spiked - Reservoir Calgon - 20 Norit MIB 2I3M Geosmin T&O Compound 11

26 Concentration, ng/l Compared Two PACs for T&O Control (Spiked #2 Lake Water Higher TOC) Task 2.2A: PAC Pretest - Lake Water Mixing = 10 minutes at 50 rpm Note: Numbers next to PAC type in legend are Raw - Hodges Calgon - 20 Norit MIB 2I3M Geosmin T&O Compound

27 PAC Summary PAC products vary in terms of effectiveness 20 minutes of simultaneous coagulation/flocculation and PAC contact time provided T&O removal In Sample #1 Reservoir water, PAC provided: 90% Geosmin removal 50% MIB removal 80% 2I3M removal In Sample #2 Lake water, TOC competition reduced effectiveness significantly for Geosmin (50-80% removal) and MIB (40% removal)

28 Superfine PAC Research by Susan Dunn under the direction of Dr. Detlef Knappe at North Carolina State University, compared the performance of as-delivered PAC with wet-milled superfine PAC. The delivered PAC was wet-milled on site. Source: Susan Dunn, Master s Thesis, 2011

29 Comparison of PAC to Superfine-PAC Superfine PAC was wet milled on site to two sizes from 5 different sources of PAC including wood-based, coconut shells, and coal. Table below is for wood-based PAC from Effect of Powdered Activated Carbon Base Material and Size on Disinfection By-Product Precursor and Trace Organic Pollutant Removal, Master s thesis by Susan Ennis Dun, North Carolina State University, PAC Superfine-PAC 1 Superfine-PAC 2 Particle Size (um) Mean diameter Range diameter BET Surface Area (m 2 /g) Micropore Volume (cm 3 /g) Mesopore Volume (cm 3 /g)

30 How did Superfine PAC compare? Wood-based PACs outperformed coal, lignite, and coconut-shell based PAC. MIB removal with PAC ranged from 33% to 69% in 60 minutes. Faster adsorption kinetics were observed with the Superfine PACs compared to their as-received forms. For example the coconutshell PAC removed only 33% but the superfine versions removed 94% under the same conditions. Source: Effect of Powdered Activated Carbon Base Material and Size on Disinfection By-Product Precursor and Trace Organic Pollutant Removal, Master s thesis by Susan Ennis Dun, North Carolina State University, 2011.

31 MIB (ng/l) Results of PAC and Superfine PAC testing 15.0 MIB Concentration Control Concentration SNR Hydrodarco Calgon WPH Superfine WPH Target PAC Dose (mg/l)

32 CONTROL AND TREATMENT OXIDANTS

33 Fishy/Swampy/Grassy T&O Control >50% Removal in CRW/SPW ClO 2 Cl 2 KMnO 4 PAC Fishy/Swampy/Grassy T&O 1-hr 5-min 25-min 1-hr 1 mg/l 25 mg/l Dimethyl Trisulfide Yes Yes Yes Yes Yes Yes 2,3-Benzopyrrole (Indole) Yes Yes Yes Yes Yes Yes Dimethyl Disulfide Yes Yes Yes Yes Yes No Cis, 3-Hexen-1-ol No No Yes** Yes NA No Cis, 4-Heptenal No No Yes** Yes Yes No Trans, 2-cis, 6-Nonadienal No No Yes** Yes NA Yes Cis, 3-Hexenyl Acetate No No No Yes* Yes Yes 1-Heptanal No No No No No Yes Trans, trans-2,4-heptadienal No No No No Yes Yes 2-Isobutyl-3-methoxypyrazine No No No No No Yes Trans, trans-2,4-decadienal No No No No NA Yes 1-Hexanal No No No No No No *Yes in 50% SPW, no in 100% CRW and 100% SPW **Yes in 100% SPW, no in 100% CRW

34 Ozone Treatment Example Cedar Water Treatment Facility Seattle, Washington

35 Log Removal UV-Peroxide AOP Removes Algal Compounds 2.0 Geosmin Removal MIB Removal Microcystin Removal Hydrogen Peroxide Dose of 5 mg/l 99.0% % Spiked Riverbank Filtration Water % % LPCB Exposure Time (min)

36 Summary of Results Treatment Technique Geosmin Removal MIB Removal TON Reduction DAF 50 75% DAF + Ozone 50 85% Biological Sand Filtration Biologically Active Carbon (BAC) Powdered Activated Carbon (PAC) 5 70% 10 80% >90% >95% 40 90% 40 75% Superfine PAC 85% UV-Peroxide AOP >95% >90%

37 THE END References and Acknowledgements: 1. Effect of Powdered Activated Carbon Base Material and Size on Disinfection By- Product Precursor and Trace Organic Pollutant Removal, Master s thesis by Susan Ennis Dun, North Carolina State University, CH2M HILL Applied Sciences Laboratory 3. Kerry Meyer/CH2M HILL, et al, Biofiltration for MIB and Geosmin Removal, ACE 2005 podium presentation. 4. Others as cited.

38 EXTRA SLIDES

39 DETECTION MEASUREMENT

40 Drinking Water Taste and Odor Wheel

41 Traditional Sensory & Chemical Evaluation Techniques Threshold Number (TON) A threshold dilution test Flavor Profile Analysis (FPA) A panel of trained analysts evaluates the T&O characteristics Standardized qualitative and quantitative T&O characterization (Flavor Rating Scale, Flavor Rating Assessment, Flavor Threshold Test) Gas Chromatography (GC)

42 New Sensory Techniques Attribute Rating Test Rating Method difference method 2-of-5 Odor Test

43 New Sensory Techniques Attribute Rating Test Paired comparison test Identify Geosmin or 2-MIB 15ng/L standard Sample is < or = or > standard Compared well with GC More effective than TON American Water (PAC testing) Korea (PAC testing)

44 New Sensory Techniques Rating Method difference method Used primarily for distribution system evaluations Compare sample at end of plant to one drawn from point in distribution system FPA basic technique, looking for difference

45 New Sensory Techniques 2-of-5 Odor Test Forced choice method 2 flasks test sample & 3 flasks control sample Blind test, group in 2 and 3, correct sort indicates a T&O change that can then be Describe odor difference in standard terms Very reliable US and Korea analyses

46 Smell Bell (River Trent)

47 Smelling the Water (Aerosol) at Osaka

48 Marconi - enose 5000 System

49 CONTROL AND TREATMENT FILTRATION AND OZONE

50 T&O Treatment Examples Southern Delivery System Lab Testing Colorado Springs, Colorado Concentration, ng/l MIB (AM) MIB (PM) Geosmin (AM) Geosmin (PM) Human Detection Limit 20 0 Raw Settled Ozonated Filtered

51 Common Causes of Taste and Odor Geosmin and MIB Geosmin (Trans-1,10-dimethyl-trans-9-decalol) MIB (2-Methylisoborneol) Produce earthy/musty odors not removed during conventional treatment Metabolic byproducts of algae (blue-green algae and actinomycetes) Occurrence seasonal (summer and fall) Geography global, significant research conducted in Japan and the U.S. Odor threshold concentration (OTC) - 2 to10 ng/l For comparison hydrogen sulfide (H 2 S) odor threshold - 5,000 ng/l

52 Current Taste and Odor Observations Surface water supplies in the Northwest are subject to seasonal T&O events due to algae Watershed influences for T&O include Storage reservoirs / forbays that favor algae proliferation Nutrient loadings (point source & non point discharges) Climate Change impact (temperature, vegetation) Wildfire Extreme Wet and Dry periods Changes in conveyance and storage Variations in run-off Monitoring programs beginning to establish baseline understanding of cycles and trends