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Water Quality Assessment of Community Systems: Preliminary Results and Human Health Implications

This presentation outlines the Source Water-Quality Assessment (SWQA) Design results for community water systems. It covers the occurrence of various compounds in source water, comparing source and finished water quality against human-health benchmarks. Key findings include the detection of emerging contaminants in both source and finished water, with most concentrations below human-health benchmarks. The study analyzed samples from multiple sites and found that nearly half of the compounds analyzed were not detected in source water. For more information on the National Water-Quality Assessment (NAWQA), visit http://water.usgs.gov/nawqa.

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Water Quality Assessment of Community Systems: Preliminary Results and Human Health Implications

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  1. United States Department of Interior Quality of Surface and Finished Water of Community Water Systems --Preliminary Results James A. Kingsbury May 11, 2006 San Jose, California

  2. Focus of Today’s Talk • Source Water-Quality Assessment (SWQA) Design • Occurrence of Compounds in Source Water • Source- and Finished-Water Quality and comparison to Human-Health Benchmarks

  3. SWQA Design • Phase 1: Samples from 9 intakes analyzed for 260 organic compounds • Phase 2: Source- and finished-water samples at 8 sitesanalyzed for selected compounds. • Monthly samples and during selected flow conditions during both phases

  4. SWQA Study Areas • 9 streams/rivers—single intake • Average Annual Water Use2 sites > 150 MGD3 sites 20-70 MGD4 sites < 10 MGD • Water Treatment7 sites use PAC or GAC1 ozone disinfection • Land UseMixed and undeveloped

  5. Samples were analyzed for:

  6. Occurrence of Compounds in Source Water • Of the 260 compounds analyzed, about 120 were not detected in any samples • Nine compounds were detected in more than half of samples collected

  7. Compounds Detected in Source Water Most Frequently Detected Emerging Contaminants Atrazine AHTN Caffeine Chloroform Deethylatrazine Metolachlor Prometon Simazine 2,4-D 2-Hydroxyatrazine AHTN Caffeine HHBC Ethyl citrate 4-Nonylphenol diethoxylate Tri(2-chloroethyl) phosphate Tris(dichlorisopropyl) phosphate Tributyl phosphate Triphenyl phosphate Cholesterol 42-70% of samples 14-54% of samples

  8. Average Concentrations of Frequently Detected Compounds are Low Note: Different symbol for each site

  9. Average Concentrations of Emerging Contaminants in Source Water are Low Note: Different symbol for each site

  10. Source- and Finished-Water Quality and Comparison to Human-Health Benchmarks MCLs—Regulated Compounds Health-Based Screening Levels (HBSLs)—Unregulated Compounds

  11. Compounds Frequently Detected in Source Water Also Present in Finished Water N~90

  12. Concentrations of Some Compounds are Similar for Source and Finished Water

  13. Emerging Contaminants Detected in Source Water also Present in Finished Water N~90

  14. Concentrations of Some Emerging Contaminants are Similar for Source and Finished Water

  15. Average Concentrations of Frequently Detected Compounds are Below Human-Health Benchmarks

  16. Conclusions • Almost half of the compounds analyzed were not detected in source water • Many compounds present in source water were detected in finished water • Average concentrations were below human-health benchmarks

  17. For More Information About NAWQA - reports, data, and programs http://water.usgs.gov/nawqa SWQA- Greg Delzer, Coordinator email: gcdelzer@usgs.gov Phone (605) 394-3230

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