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Results from Consumer Taste Tests & Flavor Profile Analysis July 2006

This presentation provides the results of a consumer acceptance test conducted on different water samples. The analysis includes taste ratings and flavor profiles to determine the most acceptable options.

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Results from Consumer Taste Tests & Flavor Profile Analysis July 2006

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  1. Results from Consumer Taste Tests& Flavor Profile AnalysisJuly 2006 Presentation to Dublin San Ramon Services District Water Committee September 21, 2006

  2. Introduction • Fall 2003, a Customer Satisfaction Survey indicated the biggest issue was drinkability (taste) of the water • December 2004, a telephone survey by conducted Fairbanks, Maslin, Maullin & Associates found DSRSD customers thought that their tap water was only fair/poor in drinkability. • November 2005, in an effort to improve the drinkability of the water, DSRSD asked The NFL for assistance in conducting a consumer acceptance test on 11 samples of water from different sources/treatments. • After reviewing results of the November test, DSRSD was interested in determining the consumer acceptance of 6 additional samples of water collected during the summer. • DSRSD requested that McGuire Malcolm Pirnie perform another FPA and evaluation of results

  3. CONSUMER ACCEPTANCE TESTOFWATERPresented to Dublin San Ramon Services District (DSRSD)September 2006

  4. Methodology • 111 Dublin residents participated • Males and Females (41%/59%) • Ages 21-65 • DSRSD Customers • 66 live in Western/Central Dublin, 26 live in Eastern Dublin, 19 live in Dougherty Valley • Drink water (any type: bottled, tap, filtered) at least once a day • No past 3 months participation in a consumer test

  5. Quantitative Taste Test Design • Respondents evaluated 6 samples on Wednesday, July 26, 2006 • Samples were served one at a time • Respondents drank as much as they needed to form an opinion, then completed a self-administered questionnaire • Four (4) ounces of each sample were served in a clear plastic cup coded with a 3-digit number • Serving order was balanced such that each sample was evaluated in each serving position approximately an equal number of times • Samples were served at room temperature • Samples were collected on July 25, 2006 and were provided by DSRSD

  6. Water Samples Tested • Turn out 2 • Turn out 5 • Mocho 4 well water • Del Valle Treatment Plant • EBMUD • San Francisco Hetch Hetchy

  7. Summary of Results • EBMUD and San Francisco Hetch Hetchy were more acceptable than all other samples in overall liking. • EBMUD was rated more acceptable than all other samples in overall flavor. • Turn out 2, turn out 5 and Mocho 4 well were rated similarly in overall liking and overall flavor. • Del Valle Treatment plant was rated lower than all other samples in overall liking, appearance, overall aroma and overall flavor.

  8. *Products within a bracket are not significantly different at the 90% confidence level

  9. *Products within a bracket are not significantly different at the 90% confidence level

  10. *Products within a bracket are not significantly different at the 90% confidence level

  11. *Products within a bracket are not significantly different at the 90% confidence level

  12. Conclusions Within DSRSD’s water supply, Turnout 2, Turnout 5, and Mocho 4 Well Water ratings were comparable, with Turnout 5 having an advantage over Turnout 2 in flavor liking. Del Valle Treatment Plant, similar to the November test, was least liked and was characterized as having a “dirty/dusty/muddy” taste.

  13. Results from Consumer Taste Tests and Focus Groups James R. Leserman and Michael J. McGuire 14

  14. Purposes of Study II • Verify 11/2005 results • Compare summer vs. late fall/winter • Determine causes of off-flavors • Recommend possible remedies

  15. Water Samples for Testing • Samples were selected to reflect and compare: • DSRSD sources (DVWTP & Mocho 4 Well) • Distribution System (2 sites) • Two “reputable” supplies (EBMWD & Hetch Hetchy) • Samples were analyzed by the Zone 7 Laboratory and a contract laboratory for a variety of parameters.

  16. NFL Flavor Rating Results

  17. NFL Findings • DVWTP had lowest rating (as it was in 11/2005) • Mocho well water was rated higher overall • For NFL flavor rating results: • Mocho well water and Distribution system sites were intermediate • EBMUD water rated the highest • Hetchy Hetch was second, better than 11/2005

  18. Effect of Geosmin on NFL Flavor Rating Geosmin OTC

  19. Effect of Chlorine on NFL Flavor Rating

  20. Effect of Chlorides on NFL Flavor Rating

  21. Effect of Hardness on NFL Flavor Rating

  22. Correlation Coefficients (r2 values) for Water Quality and NFL Flavor Rating The correlation coefficient is a statistic that gives a measure of how closely two variables are related. A correlation coefficient of +1 or -1 would indicate perfect correlation.

  23. Correlation Coefficients (r2 values) for Water Quality and NFL Flavor Rating

  24. Water Quality Impacts on Flavor Rating • NFL Flavor ratings appeared to have an inverse relationship with: • Increasing geosmin level • Increasing chlorine residual • Increasing chloride concentration • No relationship appeared to exist between NFL Flavor Rating and hardness

  25. Flavor Profile Method • Developed in 1948 by Sjostrom and Cairncross of Arthur D. Little, Inc. • Adapted to the drinking water field by McGuire and Krasner in 1981 • Expert panel of 4-6 members • Intensities determined based on standards • Sensory characteristics determined based on experience of panelists • Panel outcome based on consensus

  26. FPA Results for Del Valle WTP 11/2005 7/2006

  27. FPA Results for Mocho 4 Well 7/2006 11/2005

  28. FPA Results for San Francisco PUC 7/2006 (Hetchy Hetchy upstream of Sunol Valley WTP) 11/2005 (Hetch Hetchy/Sunol Valley WTP Blend)

  29. FPA Results for Turn Out 2 7/2006

  30. FPA Results for Pump Station 20B 7/2006

  31. FPA Results for East Bay MUD 7/2006

  32. Summary and Conclusions • For NFL flavor rating results: • DVWTP had lowest rating (as it was in 11/2005) • Mocho well water or Mocho DVWTP blends were intermediate • EBMUD water rated the Hetchy Hetch was second, better than 11/2005 • NFL Flavor ratings appeared to have an inverse relationship with: • Increasing geosmin level • Increasing chlorine residual • Increasing chloride concentration • No relationship appeared to exist between NFL Flavor Rating and hardness

  33. Summary and Conclusions (cont.) • FPA results indicate: • DVWTP sample had Earth/musty odors and off-flavors • The Mocho well sample had only slight odors and was flavor free • DSRSD distribution system samples had slight chlorine and musty odors/flavors. • New pump station had pencil shaving odors and flavors

  34. Recommendations • Continue discussions with Zone 7 to consider the implementation of treatment techniques to improve the aesthetic quality of water delivered to DSRSD, including: • Granular activated carbon or ozone/hydrogen peroxide for taste and odor control caused by geosmin and MIB • Membrane techniques to reduce mineral levels in sources • Reduction of the total chlorine residual is not recommended • Consider performing further work to compare effect of RO on Zone 7 groundwater

  35. Questions ? Contact: James R. Leserman Michael J. McGuire McGuire Malcolm Pirnie 1821 Wilshire Blvd., Suite 302 Santa Monica, CA 90403 310-829-1441 mmcguire@pirnie.com

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