1. Assessment of Protozoa in New York City’s Hillview Reservoir Kerri A. Alderisio Steve S. DiLonardo Pathogen Research, Science and Research Division New York City Department of Environmental Protection Bureau of Water Supply Water Quality NYC DEP WSTC September 15, 2009

2. Outline Background Background Objective Objective Project Design Project Design Data analysis Data analysis Results Results Conclusion Conclusion New York City Department of Environmental Protection Bureau of Water Supply Water Quality

3. LT2 – Long Term Enhanced Surface Water Treatment Rule 2 Promulgated January 5, 2006 Promulgated January 5, 2006 Purpose: ”…To improve public health protection through the control of microbial contaminants by focusing on systems with elevated Cryptosporidium risk…” Purpose: ”…To improve public health protection through the control of microbial contaminants by focusing on systems with elevated Cryptosporidium risk…” Systems with an uncovered finished water storage facility must cover or treat Systems with an uncovered finished water storage facility must cover or treat New York City Department of Environmental Protection Bureau of Water Supply Water Quality

4. CATLEFF Crypto Results 1999 - 2008 CATLEFF LT2 values and additional treatment threshold Are we a system with an elevated Cryptosporidium risk?

5. About Hillview SA 90 acres SA 90 acres 900 MG 900 MG 450 MGD input 450 MGD input Avg. residence 2d Avg. residence 2d Balancing reservoir Balancing reservoir 90 yrs continuous 90 yrs continuous Elevated berm Elevated berm New York City Department of Environmental Protection Bureau of Water Supply Water Quality

6. Basic Schematic of Hillview Reservoir Operations

7. Study Objective To determine if there is a significant increase in protozoa between Hillview Site 1 (Catskill Uptake) and Hillview Site 3 (Catskill Downtake) To determine if there is a significant increase in protozoa between Hillview Site 1 (Catskill Uptake) and Hillview Site 3 (Catskill Downtake) New York City Department of Environmental Protection Bureau of Water Supply Water Quality

8. Project Design Catskill and Delaware aqueducts above and below Hillview Reservoir for Giardia and Cryptosporidium. Catskill and Delaware aqueducts above and below Hillview Reservoir for Giardia and Cryptosporidium. Delaware bypassed the reservoir throughout the study (aside from minimal influence during high and low flows) Delaware bypassed the reservoir throughout the study (aside from minimal influence during high and low flows) Data evaluation – 2 parts Data evaluation – 2 parts New York City Department of Environmental Protection Bureau of Water Supply Water Quality

9. Part I: Initial Samples US EPA Method 1623 HV US EPA Method 1623 HV –50L filtered through HVF at 2L/ min. –IMS, IFA and DIC microscopy New York City Department of Environmental Protection Bureau of Water Supply Water Quality DescriptionSiteSample Matrix spike MS dupe DEL above Site 2 1/ wk 1/ 2wk 1/ 2mth DEL below Site 58 1/ wk 1/ 2wk 1/ 2mth CAT in Site 1 1/ wk 1/ 2wk 1/ 2mth CAT out Site 3 1/ wk 1/ 2wk 1/ 2mth

10. Part I: Initial Results Sampled Sept. 2006 – Sept. 2007 Sampled Sept. 2006 – Sept. 2007 49-51 Paired Samples 49-51 Paired Samples 12-14 MS per site 12-14 MS per site 2-3 MSD per site 2-3 MSD per site Preliminary data analysis suggested there may be more Crypto at Site 3 (CAT OUT); however, more QC, and other statistical approaches, needed to be considered Preliminary data analysis suggested there may be more Crypto at Site 3 (CAT OUT); however, more QC, and other statistical approaches, needed to be considered DEL system showed no differences, or a reduction DEL system showed no differences, or a reduction New York City Department of Environmental Protection Bureau of Water Supply Water Quality

11. Part II QC Enhancement DEL sites dropped DEL sites dropped Collection and analysis methods remained the same Collection and analysis methods remained the same New York City Department of Environmental Protection Bureau of Water Supply Water Quality DescriptionSiteSample Sample dupe MS DEL above Site 2 NANANA DEL below Site 58 NANANA CAT in Site 1 2/ wk CAT out Site 3 2/ wk NEW

12. Sample Yield per Type Part I Part II Total Paired Samples 49-514998 MS12-144558 MSD2-302-3 Sample Duplicates 04646 New York City Department of Environmental Protection Bureau of Water Supply Water Quality

13. Result Summary – Delaware (n=51, per 50L) Site 2 Crypto Site 58 Crypto Site 2 Giardia Site 58 Giardia DetectsFreq.7/5113.7%3/515.9%19/5137.3%21/5141.2% Mean0.20.060.840.98 Median0000 Std dev 0.530.241.361.45 Min0000 Max2155

14. Result Summary – Catskill (n=98, per 50L) Parts I &II Site 1 Crypto Site 3 Crypto Site 1 Giardia Site 3 Giardia DetectsFreq.7/987.1%14/10014.0%44/9844.9%37/10037.0% Mean0.070.150.940.68 Median0000 Std dev 0.260.391.411.08 Min0000 Max1264

15. Data Analysis Three Main Questions: Three Main Questions: –Is Site 3 Crypto > Site 1? –Is there a relationship with environmental variables? –Do the duplicates and MS recoveries affect the data interpretation? Statistics: Statistics: –Parametric and non-parametric tests explored –Statistician – Dr. Dennis Helsel –Modified sign test, Fong et al., 2003 New York City Department of Environmental Protection Bureau of Water Supply Water Quality

16. Data Analysis issue Traditional statistical tests Traditional statistical tests were built assuming no, or limited, ties in the data Traditional tests for paired data exclude the ties from the data analysis and only include non-tied data. Traditional tests for paired data exclude the ties from the data analysis and only include non-tied data. Most of the Crypto data here are ties (82%) and it is inappropriate to exclude them Most of the Crypto data here are ties (82%) and it is inappropriate to exclude them New York City Department of Environmental Protection Bureau of Water Supply Water Quality

17. Cryptosporidium Detection Distribution 82% = Tied data Tied data (In = Out) Modified sign test Diff. data New York City Department of Environmental Protection Bureau of Water Supply Water Quality Tied data (In = Out) Diff. Data Traditional tests

18. Data Analysis…Choices Modified sign test considers all data (blue +green) Tied data (In = Out) Diff. Traditional tests only consider data that showed a change 82% 18% New York City Department of Environmental Protection Bureau of Water Supply Water Quality (Fong et al., 2003)

19. Sign Test equivalent to Chi-square test Sign Ranked Test or Wilcoxon’s Traditional Excluding ties With many ties, these tests over-inflate the chance of Type I error Diff. data New York City Department of Environmental Protection Bureau of Water Supply Water Quality

20. Cryptosporidium Cryptosporidium Giardia Giardia Modified Sign Including All Data Therefore, Site 3 is not sig. greater than Site 1 All data New York City Department of Environmental Protection Bureau of Water Supply Water Quality

21. Is there a relationship between environmental variables and Cryptosporidium and Giardia? Variables Temperature Chlorine Residual Turbidity pH Final Filter Pressure 24 hr. precipitation Analysis Logistic regression: Model to predict probability of occurrence by fitting data to a logistic curve Used to determine if variables were related to Crypto and Giardia occurrence New York City Department of Environmental Protection Bureau of Water Supply Water Quality

22. Significance of Environmental variables Site 1 C Site 1 G Site 3 C Site 3 G TempNS ( - ) ChlorineNS ( - ) w NSNS TurbNS (+) w NS pHNSNSNSNS PressureNSNSNSNS Precip.NSNSNSNS W = weak significanceNS = not significant New York City Department of Environmental Protection Bureau of Water Supply Water Quality

23. Does intra-site variability affect inter-site variability? Sites compared Percent difference 8.7% 6.5% 4.3% New York City Department of Environmental Protection Bureau of Water Supply Water Quality

24. Bootstrapping Technique 46 sample duplicates per site 46 sample duplicates per site Assessed by a statistical random re-sampling technique Assessed by a statistical random re-sampling technique –1000 iterations each for Crypto and Giardia –no significant difference between sites for either organism Intra-sample variability does not significantly affect inter-sample variability Intra-sample variability does not significantly affect inter-sample variability New York City Department of Environmental Protection Bureau of Water Supply Water Quality

25. . New York City Department of Environmental Protection Bureau of Water Supply Water Quality Do the Matrix Spike recoveries affect Data interpretation?

26. Cryptosporidium  No significant difference in recovery between Site 1 and Site 3 (p=0.115)  Recovery had no significant influence on oocyst conclusion MS Recovery Data Test: Mann-Whitney U (nonparametric independent analysis) Giardia  Site 3 recovery > Site 1 (p=0.007)  Yet, results found no evidence Site 3 > Site 1; This further strengthens Site 3 is not > Site 1  Biologically insignificant New York City Department of Environmental Protection Bureau of Water Supply Water Quality

27. Conclusions Conclusions Modified sign test - appropriate choice Modified sign test - appropriate choice When all data are considered, Site 3 is not significantly higher than Site 1 for either Crypto or Giardia When all data are considered, Site 3 is not significantly higher than Site 1 for either Crypto or Giardia Temperature and Giardia had the most significant relationship Temperature and Giardia had the most significant relationship Duplicates and MS data support conclusion Duplicates and MS data support conclusion New York City Department of Environmental Protection Bureau of Water Supply Water Quality

28. Thank you! kalderisio@dep.nyc.gov New York City Department of Environmental Protection Bureau of Water Supply Water Quality

29. Assessment of Protozoa in New York City’s Hillview Reservoir Kerri A. Alderisio Steve S. DiLonardo Pathogen Research, Science and Research Division New York City Department of Environmental Protection Bureau of Water Supply Water Quality NYC DEP WSTC September 15, 2009