Treatment Considerations for

Surface Water T&O IssuesKim Ervin, P.E.

West Region Drinking Water Solutions Lead

May 2, 2019

Agenda

Sources and causes of taste and odor in surface water

Measurement and monitoring techniques

Control and Treatment

• Source Management

• Dissolved Air Flotation

• Biological filtration

• Activated Carbon

• Ozone

• Other oxidation (chlorine dioxide, chlorine, permanganate)

• Advanced Oxidation Process (AOP)

Sources of T&O in Surface Water

Climate change is expected to have many impacts on drinking

water supplies

• Stress on water supplies

• Increased frequency of forest fires

• Increased frequency of heavy rains

• Increased proliferation of algae & algal toxins

Lake Erie Algal Bloom, 2013, Source: NOAALake Chelan, WA Forest Fires 2015, Source: NWCC

Types of Taste

and Odor

Occurrence

Algae presents the greatest source of T&O for surface water

Global Taste and Odor Survey of Water Utilities, AWWA 2012

Primary causes of taste and odor in surface water - geosmin and MIB

• Metabolic byproducts of algae

• Geosmin and MIB are most prevalent

• Produce earthy/musty odors not removed during conventional treatment

• Occurrence – seasonal (summer and fall)

• Odor threshold concentration (OTC) -2 to 10 ng/L

• For comparison hydrogen sulfide (H2S) odor threshold - 5,000 ng/L

Algal metabolites

• Taste & Odor: Geosmin and MIB are most

problematic for WTPs

• Can also release toxins

• Produced during growth, within algal cell

• Metabolites can be released from algal

cells

– Death

– Grazing by zooplankton

– Signaling in response to environmental

factors

– Cell rupture (lysis) during water treatment

Toledo Free Press photo by Christie Materni

Algae related issues in water treatment plants

• Clogging of intake screens

• Fouling weirs/disruption of settling

• Algal mats

• Filter clogging from algae or extracellular organic matter

• Increased coagulant demand

• Increased chlorine demand

• Increased disinfection by products (DBPs)

• pH fluctuations

• Tastes and odors

• Release of algal toxins from cell lysing

9

Measurement & Monitoring Techniques

Traditional sensory & chemical evaluation techniques

• Threshold Number (TON)

– A threshold dilution test

• Flavor Profile Analysis (FPA)

– Panel of trained analysts evaluates T&O characteristics

– Standardized qualitative and quantitative T&O

characterization (Flavor Rating Scale, Flavor Rating

Assessment, Flavor Threshold Test)

• Gas Chromatography (GC)

• New techniques: attribute rating test, difference

method, 2-of-5 odor test.

Sensory methods

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

ThresholdOdor Number

2-or-5 Test Triangle Test Flavor ProfileAnalysis

(FPA)

AttributeRating Test

Flavor RatingAssessment

(FRA)

Other

12 Global Taste and Odor Survey of Water Utilities, AWWA 2012

Control and Treatment

Treatment selected to remove algae or treat toxins/T&O

Treatment Removes algae

Addresses

toxins and T&O

compounds

Source management

Clarification (DAF, Sedimentation)

Biological Filtration

Adsorption (PAC or GAC)

Oxidation (chlorine, chlorine dioxide,

permanganate, ozone)

Advanced Oxidation (UVAOP or Ozone AOP)

Source Water Management

Source water management

Operational Changes

• Reservoir by-pass

• River bank filtration

Limiting Nutrients - Controlling Phosphorus – In Lake

Treatments

• Hypolimnion Aeration/Oxygenation – limits P release

from Sediment

• Ferric Coagulation – difficult to control in anoxic areas

• Alum – aluminum toxicity

• Lime – May effectively precipitate and control P, doesn’t

lyse cells

• Dredging of sediments – can be effective longer term

• Surface Aeration – mixed results

• Hypolimnion withdrawal – removes P from anoxic, no

chemicals, requires sufficient new flow input

• Lake Flushing – effective if sufficient flow of low P water

available

• Mixing – increases epilimnion, 80% of volume mixed,

high rate of mixing, deep lakes

16

Preventive methods in use

74%

41%

15% 15%

Algicide Aeration Hypolimnetic aeration Other

• Copper sulfate

• PAK 27

• Cutrine

• Stratification

• TTHMs

• Increase DO

• Control H2S

Prevent

stratification and

increase DO

• Active mixing

• Permanganate

• PAC

• Blending

Global Taste and Odor Survey of Water Utilities, AWWA 2012

Density stratification

Epilimnion: warmest, wind mixed

Hypolimnion: cool/cold and stagnant

Thermocline: transition & separate zone

Dam

Stratification, anoxia, & nutrients

Aerobic

AnoxicDam

Sediments

Fe(II) Mn(II) NH4+ PO4

H2S

O2 sag to hypoxic

Cyanobacteria, stratification, & nutrients

Nutrient poor

Nutrient

rich

Dam

Green algae

DiatomsCyano-

bacteria

DIURNAL

CYCLE

Hypolimnetic oxygenation

Hypolimnetic Oxygenation

_______

• Destroy anoxia

• Sequester nutrients

• Limit cyanobacteria

growth

Aurora Reservoir, CO

HO

Sta

rt0

2

4

6

8

10

12

14

DO

, m

g/L

DO Surface (1 m) DO Bottom (24 m)

O2

Benefits

• 90% reduction in

T&O complaints

• 3 YR return on

$1M cost from

chemical and

GAC savings

Dissolved Air Flotation

Challenges with conventional coagulation and clarification

• Minimizing turbidity not sufficient to

remove algae and cyanobacteria.

• Mechanisms vary for cell removal.

Cyanobacteria will be the last

phytoplankton cells to be removed.

• High alum dose for anatoxin-a

• Little microcystin removal.

• Toxin release in some cases.

Winnipeg high-rate DAF• One of the first high-rate DAF

installations for a large (105 mgd) WTP

• Extensive piloting of conventional and high-rate DAF reduced construction costs

Winnipeg pilot results - DAF & ozone

0

20

40

60

80

100

120

140

160

180

2-

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-

TO

N

Raw Post DAF Post O3

Bellingham WA, Lake Whatcom

• Lake source

– Discontinued lake flushing and reduced intake flow

• Turbidity is typically low, < 0.5 NTU

• In-line filtration plant

– Reduced filter runs to 3.5 hours during algae bloom

DAF selected for algae removal

Bellingham DAF commissioning September 201728

Bellingham filter performance before and after DAF

Fall 2017 (before DAF) Fall 2018 (with DAF)

Average filter run time

(hours)12 53

Average unit filter run volume (UFRV)

(gal/hr)2,400 10,800

Filter influent turbidity

(NTU)0.48

0.1 to 0.2

(70% reduction)

Filter influent particle counts

(#/mL)3,640 100

Backwash water saved

(gal/day)300,000

29

Biological Filtration

Conventional filtration

Filtration

Rapid Mix/

Flocculation/

Sedimentation

Basin

Raw Water

Source

Chlorine

Chlorine Contact

Basin

Chlorine

Finished

Water

Storage

Chlorine

Chlorine

Chlorine

31

Biological filtration – the minimum

Filtration

Rapid Mix/

Flocculation/

Sedimentation

Basin

Raw Water

Source

Chlorine

Chlorine Contact

Basin

Chlorine

Finished

Water

Storage

32

Eliminate

upstream

chlorine addition

Biological filtration - enhanced

Filtration

Rapid Mix/

Flocculation/

Sedimentation

Basin

Raw Water

Source

Chlorine

Chlorine Contact

Basin

Chlorine

Finished

Water

Storage

O3

Ozonation

Nutrients

33

Exhausted GAC media

Add ozone and

nutrients

Use exhausted

GAC media

In pilot studies, both sand and GAC media biological filters demonstrate

reduction in T&O compounds

Sand

(20)

Sand

(80)

BAC

(20)

BAC

(80)

Sand LowTemp(20)

Sand LowTemp(80)

Sand

(20)

Sand

(80)

0

10

20

30

40

50

60

70

80

90

100

Perc

ent

Rem

oved (

%)

MIB

Geosmin

Preacclimated to

MIB and Geosmin Unacclimated to MIB and Geosmin

Activated Carbon

Powdered Activated Carbon

• Most common approach for T&O

• Usually temporary or seasonal use

• Added with other coagulants prior to

flocculation and sedimentation

• Can be very effective

• Expensive annual O&M compared to

other options

Compared two PACs for T&O control

45

65

44

11

64

20

811

0

20

40

60

80

100

120

MIB 2I3M Geosmin

Co

nce

ntr

atio

n,

ng

/L

T&O Compound

Spiked - Reservoir

Calgon - 20Norit - 20

Task 2.2A: PAC Pretest - Reservoir WaterMixing = 10 minutes at 50 rpmNote: Numbers next to PAC type in legend are doses in mg/L

45

65

44

11

64

20

811

0

20

40

60

80

100

120

MIB 2I3M Geosmin

Co

nce

ntr

ati

on

, n

g/L

T&O Compound

Spiked - Reservoir

Calgon - 20Norit - 20

Task 2.2A: PAC Pretest - Reservoir WaterMixing = 10 minutes at 50 rpmNote: Numbers next to PAC type in legend are doses in mg/LReservoir water

55 – 75%

MIB removal

75 - 90%

Geosmin removal

62

7678

27

18

32

38

32

49

0

20

40

60

80

100

120

MIB 2I3M Geosmin

Co

nce

ntr

atio

n,

ng

/L

T&O Compound

Raw - HodgesCalgon - 20Norit - 20

Task 2.2A: PAC Pretest - Lake Water

Mixing = 10 minutes at 50 rpmNote: Numbers next to PAC type in legend are

62

7678

27

18

32

38

32

49

0

20

40

60

80

100

120

MIB 2I3M Geosmin

Co

nce

ntr

atio

n,

ng

/L

T&O Compound

Raw - HodgesCalgon - 20Norit - 20

Task 2.2A: PAC Pretest - Lake Water

Mixing = 10 minutes at 50 rpmNote: Numbers next to PAC type in legend are

Lake water

(higher TOC)

40 - 55%

MIB removal

40 – 60%

Geosmin removal

Granular activated carbon• Can be used as a filter media (in

lieu of anthracite)

• Can be installed as GAC contactors downstream of filtration

38

Ozone

Advantages of Ozonation

• Taste and odor control

• Disinfection

• Coagulation/ filtration enhancement

• Oxidation

• Biological filter enhancement/

TOC removal

97%

55%

73%69%

97%

66%

82% 84%

0%

20%

40%

60%

80%

100%

120%

CH3A MIB 2I3M Geosmin

% D

es

tru

cti

on

Ozone Dose = 2.0 mg/L

Ozone Dose = 2.8 mg/L

Destruction of T&O Chemicals with Ozone in Raw OMWD Water

pH ranged from 7.3 to 7.7

Note: Results are after 3-min ozone addition followed by 7 minutes of ozone decay

Destruction of T&O in raw water

Ozone effectiveness measured with Flavor Rating AssessmentCedar Water Treatment Facility, SPU

Other Oxidants

Fishy/Swampy/Grassy T&O Control

ClO2 KMnO4 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

>50% Removal in CRW/SPW

Cl2

Summary of Results

Treatment Technique Geosmin

Removal

MIB Removal TON Reduction

DAF 50 – 75%

DAF + Ozone 50 – 85%

Biological Sand Filtration 5 – 70% 10 – 80%

Biologically Active Carbon (BAC) >90% >95%

Powdered Activated Carbon (PAC) 40 – 90% 40 – 75%

Ozone 55 – 90% 70 – 90%

UV-Peroxide AOP >95% >90%

Treatment Technologies Associated with Increasing T&O

T&

O C

oncentr

ation

BA

C

Ozone &

BA

C

PA

C &

Ozone &

BA

C

GA

C

Ozone &

GA

C

PA

C

Increasing T&O Treatment Efficiency

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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, 2011.2. CH2M HILL Applied Sciences Laboratory3. Kerry Meyer/CH2M HILL, et al, “Biofiltration for MIB and Geosmin Removal”, ACE 2005 podium presentation.4. Others as cited.

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