Assessment of Protozoa in New York City’s Hillview Reservoir

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

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

3. Water Quality New York City Department of Environmental Protection Bureau of Water Supply LT2 – Long Term Enhanced Surface Water Treatment Rule 2 • Promulgated January 5, 2006 • 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

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

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

6. Basic Schematic of Hillview Reservoir Operations

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

8. Water Quality New York City Department of Environmental Protection Bureau of Water Supply Project Design • 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) • Data evaluation – 2 parts

9. Water Quality New York City Department of Environmental Protection Bureau of Water Supply Part I: Initial Samples • US EPA Method 1623 HV • 50L filtered through HVF at 2L/ min. • IMS, IFA and DIC microscopy

10. Water Quality New York City Department of Environmental Protection Bureau of Water Supply Part I:Initial Results • Sampled Sept. 2006 – Sept. 2007 • 49-51 Paired Samples • 12-14 MS 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 • DEL system showed no differences, or a reduction

11. Water Quality New York City Department of Environmental Protection Bureau of Water Supply Part II QC Enhancement • DEL sites dropped • Collection and analysis methods remained the same NEW

12. Water Quality New York City Department of Environmental Protection Bureau of Water Supply Sample Yield per Type

13. Result Summary – Delaware(n=51, per 50L)

14. Result Summary – Catskill(n=98, per 50L) Parts I &II

15. Water Quality New York City Department of Environmental Protection Bureau of Water Supply Data Analysis • 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: • Parametric and non-parametric tests explored • Statistician – Dr. Dennis Helsel • Modified sign test, Fong et al., 2003

16. Water Quality New York City Department of Environmental Protection Bureau of Water Supply Data Analysisissue • 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. • Most of the Crypto data here are ties (82%) and it is inappropriate to exclude them

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

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

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

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

21. Water Quality New York City Department of Environmental Protection Bureau of Water Supply 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

22. Water Quality New York City Department of Environmental Protection Bureau of Water Supply Significance of Environmental variables NS = not significant W = weak significance

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

24. Water Quality New York City Department of Environmental Protection Bureau of Water Supply BootstrappingTechnique • 46 sample duplicates per site • 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

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

26. Water Quality New York City Department of Environmental Protection Bureau of Water Supply MS Recovery Data Test: Mann-Whitney U (nonparametric independent analysis) • Cryptosporidium • No significant difference in recovery between Site 1 and Site 3 (p=0.115) • Recovery had no significant influence on oocystconclusion • 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

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

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

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