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.
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 2
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 3
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 4
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 5
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 6
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 7
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 8
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 9
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 10
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 11
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 12
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 13
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 14
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 15
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 16
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 17
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 18
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)
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 19
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?
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 20
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?
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 21
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 22
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 23
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.
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 24
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 25
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 26
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 27
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 28
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 29
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 30
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 31
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 32
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 33
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 34
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 35
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 36
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 37
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 38
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.
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 39
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
T&O episode proneseason(s)
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 40
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
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 41
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
T&O episode proneseason(s)
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 42
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.
Copyright © 2012 American Water Works Association. All Rights Reserved. Page 43
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.