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Copyright © 2012 American Water Works Association. All Rights Reserved.

GLOBAL TASTE AND ODOR SURVEY OF WATER UTILITIES

FINAL REPORT

The American Water Works Association

Taste and Odor Committee

Report prepared by:

Pinar Omur-Ozbek, Ph.D.

Colorado State University

Survey and report overseen by the subcommittee:

Stephen Booth, Ph.D., P.E. Confluence Engineering Group, LLC

Steven Butterworth, Calgon Carbon Corporation

Nathaniel Dunahee, P.E., Burns and McDonnell

Monique Durand, P.E., Hazen and Sawyer

Thomas Gillogly, Ph.D., Carollo Engineers

October 12, 2012

Copyright © 2012 American Water Works Association. All Rights Reserved. Page 1

INTRODUCTION

The AWWA Taste and Odor Committee conducted a survey of drinking water

utilities, funded by the AWWA’s Technical and Educational Council, during September

2011 to May 2012, as an update of the previous survey conducted in 1989 by the AWWA

Taste-and-Odor Committee. The goal of the survey was to obtain information on the

occurrence of taste-and-odor (T&O) episodes and how the drinking water utilities

handled them and the customer complaints.

An online survey provided by Qualtrics® was utilized for this project and the

survey (questionnaire is provided at the end) was e-mailed to 982 drinking water

utilities (723 in the US, 195 in Canada, 40 in South Korea, 17 in Australia, 3 in France,

and 4 in Turkey) in early September. The contact person from each utility received the

questionnaire (as a PDF document) with a separate e-mail as well. Periodic reminders

were sent to participants and 45% of them were called by phone to encourage

participation. At the end of the project period (May 15, 2012), 478 utilities had started

the survey however only 381 responses were usable, 168 of which indicated they have

T&O issues.

Participants indicated that they have either 1) changed source waters over the

years, 2) updated the treatment plants for other reasons, 3) did not keep the data from

10 to 20 years before, and 4) they were not employed there for a long time and hence

couldn’t provide reliable data that dated back more than 5 to 10 years. This should be

taken into consideration while evaluating the results. The summary of the data collected

by this project is provided in a tabulated or graphed format below.


SUMMARY OF THE DATA COLLECTED

The survey links were specific to each participant to be able to track the source of

the data as well as to prevent multiple entries. The data was analyzed and went through

a QA/QC process to ensure inclusion of reliable data as well as the correction of units

(e.g. MGD, days, costs, etc.) for the related data. The responses obtained from the

utilities were pooled and summarized for each question and presented below.

1. Countries surveyed

The data for the participating utilities indicated that 86% of the responses came

from the US, as 74% of our list included utilities from the USA. There were some

contributions from the Canadian and Australian utilities.

2. Number of consumers served by the facility

About 30% of the utilities that responded to the survey serve less than 20,000

consumers and another 30% serve 100,000 to 500,000 customers. The majority of the

utilities serve small or mid-size towns.

# of Consumers %

< 20,000 29%20,001 - 50,000 13%50,001 - 100,000 18%100,001 - 500,000 29%> 500,000 10%

339

3713 2 1

0

50

100

150

200

250

300

350

400

USA Canada Australia South Korea France

# of

resp

onde

nts


3. Total annual budget in US $

The total annual budgets of the utilities followed a similar trend to the number of

consumers served. A small portion of the utilities have a less than $1 million or more

than $50 million budget. 30% of the utilities have a $1 to $5 million budget and another

30% have a $10 to $50 million budget.

4. Capacity of the facility

The majority of the utilities treat less than 50 MGD of water during average

conditions. Under peak demand conditions the number of utilities that serve more than

50 MGD increases about 10%.

7%

30%

17%

30%

8%8%

Annual Utility Budgets

$ < 1 million

$ 1 - 5 million

$ 5 - 10 million

$ 10 - 50 million

$ 50 - 100 million

$ > 100 million

42%

35%

9%

14%

Amount of water treated per day during average demand

<10 MGD

10 to 50 MGD

50 to 100 MGD

> 100 MGD


5. Permitted water withdrawal

Water withdrawals and the source waters varied among the utilities with different

capacities. The main supply of source water was groundwater, closely followed by lake

and river. It should be noted that some of the utilities use more than one type of source

water. For utilities less than 5 MGD capacity, groundwater was the main source followed

by lake. For utilities more than 50 MGD capacity, river followed by lake were more

common sources. For high capacity utilities all sources were used equally to meet the

demand. Most of the utilities that responded “other” as source indicated that they buy

water from other utilities and a few indicated sources as desalinated brackish water,

canals, and desalinated water.

33%

34%

11%

22%

Amount of water treated per day during peak demand

<10 MGD

10 to 50 MGD

50 to 100 MGD

> 100 MGD


25%

13%

26%

28%

8%

Types of source water

Lake

Reservoir

River

Groundwater

Other

15

19

7 6 7

0

19

53

66

32

14

96

22

30

6 6 6

0

5

10

15

20

25

30

35

<5 MGD 5-50 MGD 50-100MGD

100-500MGD

> 500 MGD

# of

resp

onse

s

Permitted water withdrawal based on source water type

Lake

Resevoir

River

Groundwater


6. Treatment processes

The majority (65%) of the utilities that responded used a conventional treatment

and about half of those utilities supplement it with activated carbon or advanced

treatment practices. Utilities use ozone and UV for disinfection as well as removal of

resistant organic compounds. Ultrafiltration and biofiltration are among the other

supplemental processes. About a third of the utilities (35%) indicated that they do not

employ conventional treatment processes and send the water directly to their

consumers after one of the following treatment methods:

Chlorination only Ion exchange Iron removal Activated carbon filtration Direct filtration Packed tower aeration Membrane treatment

35%

14%16%

35%

Treatment processes used

Conventional

Conventional + occasionalactivated carbon treatment

Conventional + advancedtreatment, please specify

Other, please explain


7. Disinfectants

Chlorine was determined as the most common disinfectant (64%) and is mainly

used as the primary choice. Chloramines (19%) and ozone (9%) follow chlorine as the

primary choices. The most common secondary disinfectant is chloramines (43%),

followed by chlorine. Other disinfectants used by the 2% of the utilities are potassium

permanganate and sodium hypochlorite.

8. Distribution system

As the sizes of the utilities varied, their distribution systems varied significantly.

The information on the distribution system is summarized below. The utilities indicated

that they replace the pipes as needed, replace certain lengths (30-40 mi) every year, or

replace mains every 5 years. The responses varied based on the budget and length of the

distribution system.

Length of DS Pipes Age of system

Top Pipe Materials

Other Pipe Materials

AvgWater Age

MaxWater Age

Min 1 mi 0 years Ductile Iron PVC 0.25 days 1 day

Avg 810 mi 55 years Cast Iron Steel 2.7 days 10 days

Max 13,041 mi 150 years Steel Cement 3 weeks 40 weeks

64%

19%9%

2% 4% 2%

31%43%

9%8% 9%

45%

15%20%

10% 10%

0%10%20%30%40%50%60%70%80%90%

100%

% o

f res

pons

es

Disinfectants usedPrimarychoice

Secondarychoice

Occasionallyused


9. Water quality

The water quality data for source water (SW) and treated water (TW) is

summarized below. As expected the water quality varied significantly.

Parameter Min Max AvgTOC (mg/L) SW 0.6 28 3.97TOC (mg/L) TW 0.3 10 2.05DOC (mg/L) SW 0.002 10 3.71DOC (mg/L) TW 0.001 5 1.86TP (mg/L) SW 0.003 2.36 0.21TP (mg/L) TW 0.00001 4 0.55TN (mg/L) SW 0.002 3 0.77TN (mg/L) TW 0.012 3.3 0.78NH3 (mg/L-N) SW 0.002 3 0.28NH3 (mg/L-N) TW 0.002 3.1 0.45H2S (mg/L) SW 0.003 7 2.07H2S (mg/L) TW 0.001 1 0.20Fe (mg/L) SW 0.00063 340 11.58Fe (mg/L) TW 0.001 40 1.00Mn (mg/L) SW 0.00012 73.1 4.06Mn (mg/L) TW 0.00002 38 0.92pH SW 5 10 7.53pH TW 6.5 9.62 7.93DO (mg/L) SW 0.2 12 7.71DO (mg/L) TW 1 11.5 7.69Conductivity (uS/cm) SW 1 1150 307.46Conductivity (uS/cm) TW 1 1818 352.44Turbidity (NTU) SW 0.03 40.6 6.00Turbidity (NTU) TW 0.01 1 0.19Temperature (C) SW 1 30 15.52Temperature (C) TW 1 30 15.68Alkalinity (mg/L as CaCO3) SW 1 350 102.58Alkalinity (mg/L as CaCO3) TW 1 380 79.58Hardness (mg/L as CaCO3) SW 1 500 124.65Hardness (mg/L as CaCO3) TW 1 400 104.56Chlr-a (mg/L) SW 0.0006 60.5 6.15Chlr-a (mg/L) TW 0.0001 1 0.28SUVA (at 254 nm) SW 0.032 75 4.94SUVA (at 254 nm) TW 0.013 2.1 1.06


10. Experience T&O?

This survey indicated that 44% of the utilities face taste-and-odor issues. These

utilities completed the following questions. For the utilities that said no to this question,

the survey was terminated. About 1% of the utilities were not sure if they have T&O issue

and hence completed the following questions as well.

11. Odors in treated water

The main types of odors detected in the drinking water were identified as earthy,

musty and chlorinous odors. Even though the utilities indicated that the data that dated

back more than 5-10 years is not very reliable, an increasing trend in these odors over

the last two decades is observed.

0

10

20

30

40

50

60

70

80

90

100

Eart

hyM

usty

Chlo

rinou

sG

rass

yFi

shy

Rott

en e

gg/S

ulfid

ePe

trol

eum

Plas

ticy

Rubb

ery

Ranc

idSe

ptic

Med

icin

alCu

cum

ber

Frui

tySw

ampy

/Dec

ayin

g ve

geta

tion

Chem

ical

Solv

ent

Woo

dyO

ther

, ple

ase

spec

ify

# of

resp

onse

s

Odors in Treated Water

This year

2 to 5 Years Ago

5 to 10 Years Ago

10 to 20 Years Ago


12. Consumer complaints due to odors

The odor complaint data indicated that for the majority of the utilities that

responded the average number of complaints were less than 10 per year for the common

odors (earthy, musty, chlorinous). Additionally, the maximum number of complaints

per year received was for the most common odors (earthy, musty, chlorinous) and the

data was more equally distributed showing about 20 to 50 complaints per year or more.

0

5

10

15

20

25

30

35

40

<5 5 to 10 10 to 20 20 to 50 > 50

# of

resp

onse

s

Average number of complaints per yearEarthyMustyChlorinousGrassyFishyRotten eggSwampyChemicalSolventPetroleumPlasticyRubberyRancidSepticMedicinal

0

5

10

15

20

25

30

<5 5 to 10 10 to 20 20 to 50 > 50

# of

resp

onse

s

Maximum number of complaints per yearEarthyMustyChlorinousGrassyFishyRotten eggSwampyChemicalSolventPetroleumPlasticyRubberyRancidSeptic


13. Tastes in treated water

The main types of tastes detected in the drinking water are determined as

chlorinous, earthy, musty, metallic and medicinal. Even though the utilities indicated

that the data that date back more than 5-10 years is not very reliable, an increasing

trend in the most common taste issues is observed. Other taste descriptors include hard,

moldy and raw water.

14. Consumer complaints due to tastes

The complaint data due to tastes indicated that for the majority of the utilities

that responded the average number of complaints were less than 10 per year for the

common tastes (earthy, musty, chlorinous, metallic). Looking at the maximum number

of complaints received for the earthy, musty, and chlorinous tastes, the response data

was skewed towards higher numbers of 50 complaints or more per year.

0

10

20

30

40

50

60

70

80

# of

resp

onse

s

Tastes in treated water

This year

2 to 5 Years Ago

5 to 10 Years Ago

10 to 20 Years Ago


15. Frequency of T&O episodes

The number of T&O episodes reported by utilities for average and maximum

conditions are tabulated below. Based on the last 5 years of data, about 80% of the

participating utilities reported less than 10 episodes per year on average; however, the

maximum numbers of complaints reported by 20% of the utilities were between 30 to

500. A slight increasing trend was observed for the recent number of episodes compared

to the data from 10 and 20 years ago. It may be that the utilities were confused about

how to define “an episode” in the past, as well as unable to provide quality data from two

decades ago.

0

5

10

15

20

25

30

<5 5 to 10 10 to 20 20 to 50 > 50

# of

resp

onse

sAverage number of complaints per year

Sweet

Salty

Bitter

Sour

Metallic

Chlorinous

Earthy/Musty

Other

02468

101214161820

<5 5 to 10 10 to 20 20 to 50 > 50

# of

resp

onse

s

Maximum number of complaints per year

Sweet

Salty

Bitter

Sour

Metallic

Chlorinous

Earthy/Musty

Other


T&O episodes per year

Avg last 5 yrs

Avg 5-10 yrs

Avg 10-20 yrs

Max last 5 yrs

Max 5-10 yrs

Max 10-20 yrs

Minimum # 0 0 0 0 0 0

Maximum # 189 199 75 590 588 100

Median # 2 2 2 3 3 3

Average # 11 13 6 24 26 11

16. Is there an increasing trend of T&O episodes?

The utilities that replied yes (15%) to this question indicated changes to the

source water and algal blooms were the reason for increased T&O episodes, however the

majority (65%) replied no to this question or not sure.

15%

65%

20%

Have you noticed an increasing trend in T&O episodes?

Yes

No

Not sure


17. Probable causes of T&O in source and tap waters

The main causes of T&O in source and tap waters were reported as algal blooms,

disinfectant residual and plumbing, followed by the distribution system, lake turnover

and decaying vegetation. Other causes were identified as:

Spring runoff Agricultural runoff Tar lined pipes Annual free chlorine flush Tank maintenance Water age New carpeting Zebra mussels Hydrogen sulfide in ground water Customers switching from well water were unaccustomed to chlorine

11%

66%

8%1% 2% 1%

14%4% 0%

21%32%

57%

34%44%

13%

0%10%20%30%40%50%60%70%80%90%

100%

% o

f res

pons

es

Likely causes of T&O in source and tap waters


18. Probable causes of T&O in the distribution system

Domestic plumbing, corrosion and biofilm growth were reported as the main

reasons for the T&O issues related to the distribution system. Also new pipe installations

and coal tar enamel lined mains were listed as other T&O causing items.

9%

25%

52% 52%

73%

11%

43%

7%

0%10%20%30%40%50%60%70%80%90%

100%

% o

f res

pons

es

Likely causes of T&O in the distribution system


19. Severity of the T&O episodes

Utilities reported that their T&O episodes were mostly minor, and the responses

were relatively uniform for the other severity ratings for data up to 10 years ago.

However, the data suggests that the severity of the episodes were much higher 10 to 20

years ago.

20. T&O episode prone seasons

The data indicates that winter is the least likely season for T&O episodes whereas

summer and fall were reported as more severe T&O episode prone seasons. Spring was

also noted as a moderate T&O episode occurring season. The results for this question

correlates well with the top likely cause of the T&O episodes which was indicated as

algal blooms that usually occur during summer and fall months.

74%

11%7% 5% 4%

50%

20%16%

9% 5%

42%

17%

30%

6% 6%

34%

16%21%

17%13%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 (minor) 2 3 (moderate) 4 5 (severe)

% o

f res

pons

es

Severity of T&O episodes

This year

2 to 5 years ago

5 to 10 years ago

10 to 20 years ago


21. Duration of T&O episodes

Based on the responses obtained for the duration of T&O events, it was

determined that for most utilities minor episodes last less than 2 weeks following a

similar trend for average episodes. However, severe episodes usually last longer than 2

weeks. The longest duration of a T&O episode was reported as 1 year.

4%

51%

34%

11%13%

52%

27%

7%

47%45%

6%2%

24%

55%

20%

1%0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

None Minor Moderate Severe

% o

f res

pons

esT&O episode prone seasons

Summer

Fall

Winter

Spring

58%

24%

5%

14%

43%

34%

16%

7%

27%21%

29%23%

0%

10%

20%

30%

40%

50%

60%

70%

< 1 week 1-2 weeks 2-4 weeks > 4 weeks

% o

f res

pons

es

Duration of T&O episodes

Minor

Average

Severe


22. Noticed a significant change in recent T&O episodes?

Similar responses were obtained for question 16 above. The main reason for T&O

episodes was identified as algae outbreaks. Utilities elaborated on their techniques to

reduce T&O by applying lake management practices, dissolved air floatation, activated

carbon, ozonation, and chlorine dioxide.

23. Importance of handling T&O issues

It was determined that, on average, about 6% of utilities do not pay attention to

handling T&O issues. However, 77% of the utilities take it very seriously.

21%

68%

11%

Have you noticed a significant change in T&O episodes?

Yes

No

Not sure

3% 3%

17%

26%

51%

How Important is handling T&O issues?

1 (not important)

2 (slightly important)

3 (moderately important)

4 (quite important)

5 (extremely important)


24. Does your facility have a public relations program?

Reflecting a similar response as the question above, 69% of the utilities indicated

that they have a public relations program to reach out to their customers and handle

their concerns and complaints.

25. How do you handle customer complaints and explain T&O

issues to consumers?

The majority of the utilities explain the situation to the consumer on the phone

and collects and analyzes samples from their tap. The utilities also indicated that they

follow up with the customers afterwards to make sure the problem is solved. About a

third of the utilities also send a newsletter or issue a news release to inform their

consumers.

Answer options:

Ignore the complaints as you cannot take any actions

Explain the issue to the customer on the phone

Send a newsletter to the consumers to explain the issue (before or after it happens)

0%

85%

16%26%

46%

77%

4%16%

0%10%20%30%40%50%60%70%80%90%

100%

% o

f res

pons

es

How do you handle consumer complaints?


Issue a news release to the local paper/TV station

Follow-up with the consumers after the issue is resolved

Take samples from the consumer(s)' house(s) and conduct sensory and/or analytical analyses

Update website, Facebook or other social media

Other, please specify: These responses included: handle by flushing the distribution system pipes

and handle by activated carbon treatment.

26. How do you record complaints?

The majority of the utilities utilize an online system to record their complaint

data in conjunction with keeping hard copies. Other responses included creating and

compiling data in one excel spreadsheet or not recording the data at all.

27. Do you record T&O complaints separately to be retrieved later?

About two-thirds (63%) of the utilities indicated that they record the T&O related

complaints separately in order to retrieve them at a later date. This practice aids in

being able to trend and track T&O related issues, generally by season.

17%

42%

67%

4%0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Record it on anotebook by hand

Record it on a pieceof paper and placein the complaints

folder

Record it on anonline systemelectronically

Other, pleasespecify

% o

f res

pons

es

How do you record/archive complaints?


28. Do you use standard descriptors for T&O complaints?

The majority (61%) of the utilities use standard descriptors for recording their

T&O complaint data. The most common standard descriptor combinations used were:

Earthy Musty Chlorine Fishy

Other standards used in survey that were also noted included: Cat urine Kerosene Algae Dirt

The following three questions were asked per request from EPA becauseAWWA and EPA are launching a program to track consumer complaints as a tool to detect intentional contamination of drinking water.

29. Are you aware of the USEPA’s efforts to use consumer

complaints as an indication of contamination?

37%

48%

15%

Aware of USEPA's efforts to use complaints as contamination indicator?

Yes

No

Not sure


30. How likely would you be to implement a system that tracks

customer complaints?

31. If you were to implement the system above, how desirable

would the built in features (work management, voice recording, GIS, etc.)

be?

4%

11%

29%42%

14%

Would implement surveillance program or system to track customer complaints?

Very Unlikely

Unlikely

Undecided

Likely

Very Likely

14%

45%

41%

For surveillance program, how important are built in features?

Not at all

Somewhat

Very


32. Did your facility undergo a major treatment process within the

last two decades to handle T&O better?

About half (47%) of the drinking water utilities indicated that they have updated

their treatment processes to better handle T&O issues. Major treatment process updates

included building or addition of:

Whole new facilities

Dissolved air flotation

Ozonation

Granular activated carbon layer to the filter

Powdered activated carbon feed

Biofiltration

Membranes (nanofiltration, microfiltration)

Reverse osmosis softening treatment

New potassium permanganate building

Copper sulfate addition to the reservoir

Switched to chloramines

Switched to a different source water

Changed intake location

33. Treatment methods and their efficiency to remove T&O

The top three T&O removal treatment methods reported were filtration,

flocculation and powdered activated carbon. The least applied treatment methods

included super chlorination, UV, softening and chlorine dioxide. Ozonation, GAC/PAC,

and post chlorination were reported to achieve more than 75% removal of the T&O.

Softening, pH adjustment and corrosion inhibitor application were reported as not

efficient methods. Other methods employed by a few of the utilities include dissolved air

flotation, permanganate oxidation and purchasing water from another utility.


34

1915

51

35

52

35

7

24

46

26

2

3429

20

50

9

0

15

22

10

0

10

20

30

40

50

60

Blen

d so

urce

wat

ers

Pre-

sedi

men

tatio

n

Aera

tion

Rapi

d m

ix /

flocc

ulat

ion

Pre-

chlo

rinat

ion

Filtr

atio

n

pH a

djus

tmen

t

Soft

enin

g

Gra

nula

r act

ivat

ed c

arbo

n

Pow

dere

d ac

tivat

ed c

arbo

n

Pota

ssiu

m p

erm

anga

nate

Supe

r chl

orin

atio

n

Post

chl

orin

atio

n

Chlo

ram

ines

Ozo

natio

n

UV

Hyd

roge

n di

oxid

e

Chlo

rine

diox

ide

Ion

exch

ange

sof

teni

ng

Mem

bran

e fil

trat

ion

Corr

osio

n in

hibi

tor

Oth

er, p

leas

e sp

ecify

# of

resp

onse

sEmployed treatment methods


14

3 4 5 46

3 2

11

23

6

1

5 68

35

31

8

0

5

10

15

20

25

Blen

d so

urce

wat

ers

Pre-

sedi

men

tatio

n

Aera

tion

Rapi

d m

ix /

flocc

ulat

ion

Pre-

chlo

rinat

ion

Filtr

atio

n

pH a

djus

tmen

t

Soft

enin

g

Gra

nula

r act

ivat

ed c

arbo

n

Pow

dere

d ac

tivat

ed c

arbo

n

Pota

ssiu

m p

erm

anga

nate

Supe

r chl

orin

atio

n

Post

chl

orin

atio

n

Chlo

ram

ines

Ozo

natio

n

Chlo

rine

diox

ide

Mem

bran

e fil

trat

ion

Corr

osio

n in

hibi

tor

UV

Oth

er, p

leas

e sp

ecify

# of

resp

onse

sMost effective treatment method


Treatment Efficiencies reported (min/max/average) as:

Blend source waters %

Pre-sedimentation % Aeration %

Rapid mix / flocculation %

Min 10 Min 5 Min 10 Min 10Max 95 Max 80 Max 80 Max 95Average 58.2 Average 40 Average 40 Average 59

Pre-chlorination % Filtration %pH adjustment % Softening %

Min 5 Min 5 Min 0 Min 5Max 100 Max 100 Max 5 Max 5Average 46 Average 45 Average 8 Average 5

GAC % PAC %Potassium permanganate % Post chlorination %

Min 10 Min 5 Min 50 Min 0Max 100 Max 100 Max 90 Max 100Average 82 Average 69 Average 60 Average 67

Chloramines % Ozonation %Chlorine dioxide %

Membrane filtration %

Min 20 Min 90 Min 25 Min 20Max 100 Max 100 Max 50 Max 100Average 62 Average 96 Average 37.5 Average 63

Corrosion inhibitor %Min 0Max 5Average 2.5


34. Do you apply any preventive methods?

Only about one-third (29%) of the utilities apply preventive methods to reduce

T&O issues. The most common method is application of algicide and the other methods

are given below.

The most common algicides used are: Copper sulfate PAK 27 Cutrine

Aeration was used as a preventative method for reasons such as: Stratification TTHM’s To increase DO levels To control H2S levels

Hypolimnetic aeration was used to prevent stratification and increase DO

Other preventative methods used: Active mixing KMnO4

PAC Source water blending

74%

41%

15% 15%

0%

20%

40%

60%

80%

100%

Algicide Aeration Hypolimneticaeration

Other

% o

f res

pons

es

Preventative methods employed


35. Annual cost of handling T&O ( in US Dollars)

Based on the limited data provided by the utilities, the expenditures based on

severity of the T&O episode follow a weak trend. The data indicates that even severe

episodes may be handled with a low budget. The cost data gathered for other

components of handling T&O episodes are presented below.

20%13%

23%13%

30%

0%

16%11% 11%

16%26%

21%19%6%

0%6%

25%

44%

0%10%20%30%40%50%60%70%80%90%

100%

< $50 $50 - $100 $100 -$500

$500 -$1000

$1000 -$5000

> $5000

% o

f res

pons

es

Handling consumer complaints ($)

Minor

Average

Severe

46%

4%8%

13%17%

8%4%

35%

5%10% 10% 10%

25%

5%

31%

0%

15%

8%

15%23%

8%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

< $50 $50 -$100

$100 -$500

$500 -$1000

$1000 -$5000

$5000 -$25000

> $25000

% o

f res

pons

es

Sensory or instrumental analysis costs ($)

Minor

Average

Severe


About 10% of the utilities indicated that they spent $50,000 to $4.5 million

dollars in capital costs to update their treatment units to handle T&O issues.

71%

12% 12%6%

33%

11%17%

28%

11%

38%46%

15%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

< $50 $50 -$100

$100 -$500

$500 -$1000

$1000 -$5000

$5000 -$25000

> $25000

% o

f res

pons

esPreventive method related costs ($)

Minor

Average

Severe

46%

25%21%

8%

25%25%

15% 15%

5%

15%24%

6%

18% 24%

12%18%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

<$1000 $1,000 -$10,000

$10,000 -$50,000

$50,000 -$100,000

$100,000 -$500,000

> $500,000

% o

f res

pons

es

Treatment: operational and maintenance costs ($)

Minor

Average

Severe


36. Tests to monitor T&O issuesAbout a third (29%) of the utilities do not conduct any testing to monitor T&O

issues; however, the rest of the utilities employ sensory, instrumental and biological

testing (alone or in combination with each other) to help stay on top of T&O issues.

Other tests to monitor/detect T&O issues include:

Source water monitoring

Customer monitoring

37. Regular testing for specific T&O compounds

More than a third (38%) of the utilities test for specific T&O compounds such as:

Geosmin 2-MIB Iron Chlorine residual Algae Chlorophyll-a

48% 46%

26%

6%

29%

0%10%20%30%40%50%60%70%80%90%

100%

% o

f res

pons

es

Testing used to monitor T&O


38. Sensory methods

About 40 % (69 responses) of the utilities responding to this survey reported that

they conduct sensory methods to test for T&O. Most of the utilities (85%) that conduct

sensory testing employ the threshold odor number (TON) test as their main sensory

test. Other more elaborate testing methods, such as flavor profile analysis (FPA), are

used by a lot fewer utilities. Other methods conducted were reported as informal smell

surveys and staff T&O panels.

The utilities indicated that the most effective method to test for T&O is the

threshold odor number, followed by the FPA.

85%

4% 2%

19%

0%9%

13%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

% o

f res

pons

es

Sensory methods used to test for T&O compounds


39. Sensory methods used for each treatment stage

The most common sensory methods employed to detect the T&O of the samples

from different stages of water treatment were TON, followed by FPA, as shown in the

previous question above.

56%

6%4%

21%

2% 4%7%

Most effective method for sensory T&O testingThreshold Odor Number (TON)

2-of-5 Test

Triangle Test

Flavor Profile Analysis (FPA)

Attribute Rating Test (ART)

Flavor Rating Assessment (FRA)

Other, please specify

0

5

10

15

20

25

30

35

40

TON 2-of-5 Triangle FPA FRA Other (asstatedabove)

# of

resp

onse

s

Methods used for each stage

Source water

Treated water

Samples from thetreatment units

Samples from thedistribution system

Samples from theconsumers' taps


40. Frequency of sensory testing

During a T&O episode, the majority of the utilities (78%) conduct daily sensory

testing. During T&O prone seasons more than half of the utilities continue their daily

testing and more than a quarter perform testing twice a week. The rest of the time a

considerable number (40%) of the utilities continue performing daily sensory testing.

41. Do the sensory test results correlate with consumer complaints?

Utilities indicated that when they detect off-flavors in the raw or finished water

they are very likely to get complaints. However some of them indicated that the masking

effect of higher levels of chlorine in the finished water may lead to false results,

preventing them from detecting the T&O before the consumers.

78%

14%4%

2% 2%

40%

19% 17%6% 10% 6% 2%

52%

27%

11% 7%2%

0%10%20%30%40%50%60%70%80%90%

100%

Everyday

Twice aweek

Once aweek

Twice amonth

Once amonth

Everythree

months

Every sixmonths

% o

f res

pons

es

Frequency of sensory testing

During an episode

Generally

T&O episode proneseason(s)

47%

20%

33%

Do the sensory test results correlate with consumer complaints?

YesNoNot sure


42. Results for the sensory tests

0

2

4

6

8

10

≤ 1 1 to 2 2 to 4 4 to 8 8 to 16 16 to32

32 to64

64 to128

128 to256

# re

spon

ses

TON - Source Water

Normal

T&O Episode

0

2

4

6

8

10

≤ 1 1 to 2 2 to 4 4 to 8 8 to 16 16 to 32 32 to 64

# re

spon

ses

TON - Treated Water

Normal

T&O Episode

01234567

≤ 1 1 to 2 2 to 4 4 to 8 8 to 16

# re

spon

ses

TON - Distribution system

Normal

T&O Episode


43. Chemical/analytical tests

About half of the utilities that completed this survey (84 utilities) indicated that

they conduct chemical tests for T&O. As illustrated by the results below, 48% of the

utilities do the tests in their own lab and another 48% send the samples to an outside

lab. A small portion of them use a combination of outside resources and their own labs.

44. Analytical methods used by the utilities

Based on the limited responses (by only 30 utilities) to this question, the

common/popular analytical method to test for volatile organics is determined as solid

phase micro-extraction coupled with gas chromatography/mass spectrometry.

01234567

≤ 1 1 to 2 2 to 4 4 to 8

# re

spon

ses

TON - Consumers' tap

Normal

T&O Episode

48%

48%

4%

Conduct in house tests or send to outside lab?

Conduct tests in thefacility's lab

Send the samples to anoutside lab

Other, please specify


45. Methods and instruments used by the outside laboratory

Utilities were almost evenly split for this question and reported that they either

know the methods and instruments used by the outside lab (47%) or they do not (53%).

The methods used by the laboratories were reported as solid phase micro-extraction

coupled with gas chromatography/mass spectrometry or closed loop stripping.

46. T&O compounds detected in source or treated water

The utilities reported several compounds that were detected/measured in their

source and treated waters. The reported compounds and their concentrations are given

below. Other compounds measured/detected were reported as limonene, propanol,

naphthalene, mycrocystis and an unidentified compound.

5

0

8

11

2 2

11

2 24

7

0

2

4

6

8

10

12#

of re

spon

ses

Analytical methods used


Concentrations during average conditions:

Free chlorine (mg/L) Chloramines (mg/L) Geosmin (ng/L)2-Methylisoborneol (ng/L)

Min 0 Min 0 Min 0 Min 0Max 3 Max 2.8 Max 13 Max 15Average 0.93 Average 1.88 Average 5.7 Average 5.2Responses 24 Responses 9 Responses 20 Responses 18

Iron (mg/L) Copper (mg/L) Manganese (mg/L)Min 0.0005 Min 0.0018 Min 0.003Max 0.3 Max 0.103 Max 2Average 0.12 Average 0.037 Average 0.3Responses 10 Responses 6 Responses 9

Concentrations during high conditions:

Free chlorine (mg/L) Chloramines (mg/L) Geosmin (ng/L) 2-Methylisoborneol (ng/L)Min 0.2 Min 2.3 Min 8 Min 1Max 3.4 Max 5.1 Max 4,600 Max 400Average 1.8 Average 3.5 Average 411 Average 78.5Responses 19 Responses 10 Responses 23 Responses 21

Iron (mg/L) Copper (mg/L) Manganese (mg/L)Min 0.001 Min 0.054 Min 0.035Max 2.1 Max 1.5 Max 8Average 0.5 Average 0.5 Average 1.5Responses 8 Responses 4 Responses 7

34

14

3126

1 2

158

13

5

05

10152025303540

# of

resp

onse

s

Detected T&O compounds


Concentrations after treatment:

Free chlorine (mg/L) Chloramines (mg/L) Geosmin (ng/L) 2-Methylisoborneol (ng/L)Min 0.05 Min 1.8 Min 2 Min 0Max 2.5 Max 3.5 Max 30 Max 26Average 1.3 Average 2.5 Average 8.7 Average 6.3Responses 9 Responses 11 Responses 13 Responses 12

Iron (mg/L) Copper (mg/L) Manganese (mg/L)Min 0 Min 0.05 Min 0Max 0.3 Max 0.05 Max 0.05Average 0.1 Average 0.05 Average 0.015Responses 4 Responses 1 Responses 5

47. Algal toxins

Fifty-six utilities responded to this question and only 12 of them indicated that

they test for algal toxins. The commonly tested toxins include cyanotoxins and

microcystins.

48. Frequency of analytical testing

During a T&O episode, the majority of the utilities conduct analytical testing at

least once a week. Under normal conditions, once a week and once a month are the most

common sampling frequencies. Utilities mostly conduct analytical testing during T&O

episode prone season(s) once a week.


49. Biological testing

Thirty-seven utilities (about 20%) reported that they conduct biological tests to

monitor T&O issues. The utilities mainly perform algae counts and identification. The

responses to this question were limited, but the data collected indicates that algae are

the more common cause of T&O. Other methods include testing for zooplankton.

40%

21% 26%

2%7%

13%

3%

29%

11%

32%

5% 4% 4%

17%11%

42%

14% 14%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Everyday

Twice aweek

Once aweek

Twice amonth

Once amonth

Everythree

months

Everysix

months

Once ayear

% o

f res

pons

esFrequency of analytical testing

During an episode

Generally



50. Monitor specific types of algae to monitor T&O?

The majority of the utilities (78%) that conduct biological testing monitor for

specific types of algae. The specific algae types include:

Blue green and/or flagellated algae

Diatoms

51. Organisms detected and identified as causing T&O

Based on the responses to question 50, organisms detected and identified as

causing T&O were:

Blue green algae

Anabaena

Mycrocytis

Ocsillatoria

Synura

Chrysopherella

Asterionella

Synedra

Ceratium

Staurastrum

Mallomonas

Aphanizomenon

35%

10%

90%

16%

0%10%20%30%40%50%60%70%80%90%

100%

Planktontesting

Benthicorganism

testing

Algae countsand

identification

Other, pleasespecify

% o

f res

pons

es

Biological tests performed


52. Frequency of biological testing

The most common frequency for biological testing under all conditions was

reported as once a week. As expected, the frequency increased to every day during a

T&O episode.

32%27%

36%

5%9%

5%

32%

14%

41%

6%

17%

50%

17%11%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Every day Twice aweek

Once aweek

Twice amonth

Once amonth

% o

f res

pons

es

Frequency of biological testing

During an episode

Generally



SUMMARY AND IMPORTANCE OF FINDINGS

This T&O survey provides valuable information for drinking water utilities to

understand the main causes of T&O occurrences, and to help determine the most

efficient and cost effective methods to handle episodes. The data gathered by this survey

indicated that almost one-half of the utilities face some form of T&O issues. The

common odor descriptors in treated water included chlorinous, earthy and musty. The

common taste descriptors were similar to odors, with the addition of a metallic taste.

Even though a clear trend was difficult to observe from the collected data due to changes

in source water, types of treatment processes, and other outside factors, the presence of

tastes and odors in treated water show an increasing trend over the last two decades.

The major cause of taste and odor issues were linked to disinfectant residual, algal

blooms and distribution system/plumbing materials.

Approximately 75% of the utilities reported that their T&O episodes were mostly

minor. Summer and fall months were indicated as T&O prone seasons with average

T&O episode durations usually less than 1-2 weeks. Even though the surveyed utilities

do not experience serious T&O issues often, being able to handle T&O episodes is very

important to them. The survey participants use many methods to reach out to the

customers, including newsletters, news releases and websites. These methods are used

to inform their customers when a T&O episode has occurred and to help explain why the

episode happened, which the utilities find helps to maintain confidence with their

customers.

The best treatment methods reported for T&O control are filtration, flocculation

and activated carbon treatment. Approximately 30% of the utilities take preventive

actions such as the use of algicides and aeration of their source waters. While the cost to

handle complaints, conduct analyses and apply preventive methods is anywhere from

$50 to $25,000 annually for utilities, the treatment related costs increased to more than

$500,000 per year in some cases for even minor T&O issues due to treatment updates

and upgrades. Some form of sensory, chemical and/or biological testing is employed by

approximately 70% of the utilities. The most commonly investigated compounds include

algal odorants (geosmin and 2-MIB), iron, manganese and copper. Threshold odor

number was used to evaluate the odors in source and treated waters and was indicated

as the most effective method for T&O analysis, followed by flavor profile analysis.


Utilities were evenly split between conducting their own tests or using outside

laboratories for chemical analyses. Volatiles were analyzed by solid phase micro-

extraction coupled with gas chromatography/mass spectrometry. Biological testing

focused on algal identification or counting. Blue-green algae (cyanobacteria) were

identified as the most problematic algae for T&O related issues. The testing frequency

increased to almost every day during a T&O episode, and conducted more frequently

during T&O prone seasons.

Utilities serving 21st century customers have higher standards to meet because

the customers not only expect the tap water to be safe, but also to be pleasant tasting.

Fortunately, utilities now have access to improved detection and treatment techniques

to handle T&O issues. The data gathered by this survey indicates that the use of

preventive methods and sensory and analytical techniques coupled with efficient

treatment methods will allow utilities to provide better tasting water to their customers.

SUGGESTIONS FOR FUTURE T&O SURVEYS

Online surveys work well, however, e-mailing the full survey as a word document or

PDF allows the responders the option to collect data on their own time and could

enhance contributions.

Refine the survey questions and minimize the number of questions.

Provide clear cut answer options and define terms when appropriate.

Allow at least nine months for completion of the survey.

Calling and sending reminders to the potential responders help improve the

response rate.

ACKNOWLEDGEMENTS

We would like to thank our Program Manager, Liz Ralph, for her support, input

and guidance throughout the project. We also thank Ari Copeland for reviewing the

report.

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