Transcript Relationships Between Fecal Indicator Bacteria Prevalence in

+
Relationships Between
Fecal Indicator Bacteria
Prevalence in Private Water
Supplies and Demographic
Data in Virginia
Tamara Smith, E.I.
M.S. Candidate, Virginia Tech
2012 Water and Health Conference
Chapel Hill, NC
31 October 2012
+
Presentation Outline
 Introduction-What
are Private Drinking Water Systems?
 Research
Objectives- What Do We Hope To Accomplish?
 Methods-
How It Happens
 Initial
Results- What Have We Done So Far?
 Conclusions-What
Did We Learn?
 Future Work-What’s
Next?
+
Introduction
+
What are Private Drinking Water Systems?
 Serves
< 25 persons and has
< 15 connections
 Types:
 Drilled, dug, and
bored wells
 Springs
 Cisterns
 Depend
 If
on groundwater
properly maintained, these
systems can provide potable
drinking water.
+
Potential Problems
 23
and 45 million Americans rely on private water supply
systems for drinking water.
 Not
regulated by the Safe Drinking Water Act (SWDA) for two
main reasons:
Private property rights
 Dispersion of private water systems nationwide

 Over
the past 30 years, the proportion of Centers of Disease
Control (CDC) annual reported outbreaks associated with
private water supplies has increased.1
1. Craun et al. (2010)
+
Potential Problems Cont’d
 Previous
studies have attempted to correlate well construction and
local geology with observations of water quality.
Aquifer composition(such as limestone and fractured rock) can increase
contaminant exposure. 2
 Poor construction and proximity to potential sources of contamination
(e.g. septic tank) can lead increased contaminant exposure.3

 Although
inadequate water and sanitation is often linked to poverty,
there have been no studies linking private system water quality and
demographic data.
2. Brunkard et al. (2011) 3. Swistock and Sharpe (2005)
+
Private Drinking Water Systems in Virginia:
A Particular Concern

Over 1.7 million households rely on private
water systems for drinking water.4

The majority of households in 60 out of 95
counties rely on private water systems.5

In 52 counties, the number of households
being served by private water supplies is
increasing at a rate greater the households
currently being joined to municipal
systems.5
4. Gatseyer and Vaswani (2004) 5. US Census Bureau (1990)
Scientific Investigations
Report (2009)
+
Overall Goal and Objectives

Identify relationships between the prevalence of fecal indicator
bacteria from privately supplied water systems and demographic
data with the following objectives:
1)
2)
3)
Quantification of total coliform (TC) bacteria and E. coli (EC)
prevalence in water samples from private systems collected from the
point-of-use;
Identification of possible correlations between demographic data and
fecal indicator bacteria;
Applying a chemical source tracking technique (i.e. fluorometry) to
identify possible human contamination (i.e. sewage intrusion).
+
Methods
+
Virginia Household Water Quality Program
(VAHWQP)
 VAHWQP’s
objective is to improve the water quality and health of
Virginians using private water supplies.
A
program a part of Virginia Cooperative Extension.
 Currently
partnering with the Southeast Rural Community Project
(SERCAP).
+
VAHWQP-Drinking Water Clinics
1. Kickoff
Meeting
2. Sample
Collection
3. Analysis
4. Interpretation
Meeting
+
Counties that Participated in 2012 Drinking
Water Clinics
• 28 Counties
• n=543
+
Sample Collection
 Survey
in kits contains:
 Homeowner perception of
water quality
 Homeowner-supplied
demographic data
+
Sample Collection and Analysis
2 Bottles
(Bacterial
Analysis)
100 mL- TC/EC
Presence &
Quantification
250 mL- ST
Household
Samples (Four
Bottles)
2 Bottles (Other
Analysis)
pH, Conductivity,
Heavy Metals,
etc.
+
TC/EC Detection & Quantification

Presence- Colilert (IDEXX)
defined substrate technology

Quantification-Quanti-tray/2000
(MPN)

~24h incubation

~35°C±0.5°C
+
Chemical Source Tracking

Source Tracking is used to determine the source of fecal bacteria. Usually a
specific marker is used that is linked to a specific source of fecal
contamination.

Typically used for for surface waters, but are starting to become used for
drinking water.

Fluorometry analyzes fluorescence in a sample. Optical brighteners are
likely indicative of fecal contamination via septic sewage.
+
Initial Results
+
Primary and Secondary Maximum
Contaminant Levels


Maximum Contaminant Levels (MCL)
refer to the highest that is allowed in
drinking water by the US EPA.
Primary MCLs are standards that are
health-based. These include Total
Coliforms, E. coli, and Nitrate.

Secondary MCLS are non-enforceable
guidelines based on a contaminants’
cosmetic and aesthetic effects.

Although not applied to private systems
can be used as a guideline
4. US EPA (2011)
Some MCLs of Concern4
Contaminant
MCL
Total Coliforms
No more than 5%
positive samples in
one month.
Fecal Coliforms/E.
coli
Any sample tested
positive from a
repeat of total
coliform or the
reverse is true, then
is in violation of
MCL.
Nitrate
10 mg/L
+
Objective 1: Overall Prevalence of Fecal
Indicator Bacteria Positive Samples
2012 Drinking Water Clinics (n=543)
Counties
Participating
28
Percent Positive for
TC
38%
Average TC
Concentration
~118 MPN/ 100 mL
Percent Positive for
EC
6%
Average EC
Concentration
~11 MPN/ 100 mL
Nitrate
Below MCL
Average Nitrate
Concentration
0.80 mg/L
 Although
these bacteria
prevalences seem high, it
coincides with previous studies
in private water
supplies5,6,7,8,9,10,11
5. Sandhu et al. (1979) 6. Lamka et al. (1980) 7.
Sworobuk et al.( 1987) 8. Bauder et al. (1991) 9. Kross
et al. (1993) 10. Gosselin et al. (1997) 11. Borchardt et
al. (2003)
Objective 1: Cumulative Distribution for Total
Coliform Concentrations
2500
2000
TC MPN/ 100 mL
+
2500
1500
2000
1000
1500
500
1000
0
0.6
500
0.7
0.8
0.9
1
0
-500
0
0.2
0.4
0.6
Percentile
0.8
1
 Non-zero
samples around 61st
percentile.
 13
samples above detection limit
+
Objective 1: Cumulative Distribution for E. coli
Concentrations
2500
EC MPN/ 100 mL
2000
2500
1500
2000
1000
1500
500
1000
0
0.9
500
0
-500
0
0.2
0.4
0.6
Percentile
0.8
1
0.95
1
 Non-zero
samples around 94th
percentile.
1
sample above detection limit
Objective 2. Total Coliform Presence by
Income Level
Percent Positive for Each
Category
+
100%
n=476
90%
80%
70%
n=35
60%
n=88
50%
40%
n=86
n=15
n=252
30%
20%
10%
0%
<$10K
$11K-$24K
$25K-$40K
$41K-$64K
Income Level
>$65K
Objective 2. E. coli Presence by Income Level
Percent Positive for Each
Category
+
100%
n=476
90%
80%
70%
60%
50%
40%
30%
20%
10%
n=15
n=88
n=35
n=86
n=252
0%
<$10K
$11K-$24K
$25K-$40K
$41K-$64K
Income Level
>$65K
Objective 2. Total Coliform Presence by
Education Level
Percent Positive for Each
Category
+
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
n=516
n=7
n=17
n=81
n=116
n=146
n=149
In School Some High
Now
School
High
School
Graduate
Some
College
Education Level
College
Graduate
Post
College
(MS, PhD)
Objective 2. E. coli Presence by Education
Level
Percent Positive for Each
Category
+
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
n=516
n=7
n=17
In School Some High
Now
School
n=81
High
School
Graduate
n=116
Some
College
Education Level
n=149
n=146
College
Graduate
Post
College
(MS, PhD)
+
Objective 2. Correlations Between Bacteria
Prevalence and Demographics

Chi-squared Test were used to
determine differences in
categorical distributions between
 TC/EC Presence and Income
Level
 TC/EC Presence and Education
Level
Alpha= 0.05
For TC Presence
P-value
Income Level
0.0025
Education Level
0.0516
For EC Presence
P-value
Income Level
0.0119
Education Level
0.0730
+
Objective 3. Application of Chemical Source
Tracking Technique

11/543 were tested positive for optical brighteners

45.5% positive for TC; 36.4% positive for EC

Average TC concentration: 503.1 MPN/100 mL

Average EC concentration: 249.6 MPN/100 mL

27% of systems have some type of treatment (i.e. chlorination, filtering, etc.)

18.2% of systems 100 ft or less to septic system drain field

County Location: 27.3% Lancaster, 27.3% Northumberland, 18.2% Tazewell, 18.2%
Charlotte

72.7% households <$65K; 18.2% >$65k
+
Conclusions

There is presence of total coliform and E. coli bacteria in private drinking water
supplies.

TC and EC presence are statistically different between income levels, but not
necessarily for education levels.

Fluorometry positive samples have some similarities in location and income level,
but not all tested positive for E. coli contamination.
+
Future Work

Continuing analysis of 2012 Drinking Water Clinic Data

Analysis of E. coli-positive samples for Bacteroides human marker (BacHum)
via qPCR

Further explore relationships between fluorometry positive samples

Statistical correlations between E. coli incidence and self-reported illness
+
Acknowledgements

Dr. Leigh-Anne Krometis

All the members of my research committee: Dr. Brian Benham, Dr. Charles
Hagedorn III, and Susan Marmagas

VAHWQP & The Krometis Research Group

Sponsor: USDA-NIFA
2011-46100-31115
Rural Health Education Program Competitive Grant No.
+
Questions & Discussion
[email protected]
+
Types of Sources
Source
Number of Samples
Percent
Drilled Well
400
74%
Dug/Bored Well
79
15%
Unknown Wells
44
8%
Spring
12
2%
Other
7
1%