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?
What are Private Drinking Water Systems? • Serves < 25 persons and has < 15 connections • Types: • Drilled, dug, and bored wells • Springs • Cisterns • Depend on groundwater • If 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 Scientific Investigations Report (2009) 4. Gatseyer and Vaswani(2004) 5. US Census Bureau (1990)
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: • 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).
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
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, butare starting to become used for drinking water. • Fluorometry analyzes fluorescence in a sample. Optical brighteners are likely indicative of fecal contamination via septic sewage.
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)
Objective 1: Overall Prevalence of Fecal Indicator Bacteria Positive Samples • Although these bacteria prevalencesseem 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 • Non-zero samples around 61st percentile. • 13 samples above detection limit
Objective 1: Cumulative Distribution for E. coli Concentrations • Non-zero samples around 94th percentile. • 1 sample above detection limit
Objective 2. Total Coliform Presence by Income Level n=35 n=88 n=86 n=15 n=252
Objective 2. E. coli Presence by Income Level n=88 n=35 n=15 n=86 n=252
Objective 2. Total Coliform Presence by Education Level n=7 n=17 n=81 n=116 n=146 n=149
Objective 2. E. coli Presence by Education Level n=7 n=116 n=81 n=17 n=146 n=149
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
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 Rural Health Education Program Competitive Grant No. 2011-46100-31115