Cyanobacterial Monitoring and Response Approaches by San Francisco Public Utilities Commission

Transcription

1 Services of the San Francisco Public Utilities Commission Cyanobacterial Monitoring and Response Approaches by San Francisco Public Utilities Commission Gregg Olson, P.E. Associate Engineer, Water Quality Division San Francisco Public Utilities Commission Annual Water Quality and Technology Workshop November 8,

2 Acknowledgements Natural Resources Division Andie Irons, Randy Renn, Brian Sak Water Quality Engineering Manouchehr Boozarpour, Andrzej Wilczak (retired), Enio Sebastiani, George Leung Millbrae Laboratory Megan Tran (geosmin/mib), Mike Giles (developing/validating LC/MS method for algal toxins) 2

3 Outline Background Algae overview Algae characteristics by SFPUC source water Algal Toxins Monitoring, 2015 to 2017 Monitoring and response plan, 2018 to 2019 Next Steps 3

4 Algae Overview Diatoms Filter-cloggers Blue-green algae, aka cyanobacteria T&O compounds Geosmin/MIB DL = 3 ppt (ng/l) Human sensitivity to geosmin/mib (WRF, 2013): Odor threshold conc. = 5 to 10 ppt (50% of population can detect) Algal toxins (cyanotoxins) Microcystins Hepatotoxin (liver toxin) USEPA Health Advisory = 0.3 ug/l (children < 6 years old) Cylindrospermopsin Hepatotoxin (liver toxin) USEPA Health Advisory = 0.7 ug/l (children < 6 years old) Anatoxin-a and Saxitoxin Neurotoxins No USEPA or California HAs (HAs in some states, other countries) Other algae (green algae, golden algae) 4

5 Algae Characteristics by SFPUC Source Water Hetch Hetchy Reservoir San Andreas Reservoir Calaveras Reservoir Source Hetchy West Bay Crystal Springs/San Andreas East Bay Calaveras/San Antonio Conditions very low nutrients (oligotrophic) low nutrients (low algal production) ample nutrients (moderately eutrophic) Dominant Algae Type no algae diatoms (filter-cloggers) blue-green algae (cyanobacteria) Anabaena Microcystis Other BGA T&O Toxins none none geosmin (T&O) microcystins (toxin) No T&O No toxins 5

6 Long-Term Trend at Calaveras Reservoir Blue-greens 100X increase over 20-year period Special Conditions Dam improvement (low water level) 4-yr drought High air temps 6

7 Algal Toxin Monitoring, Background & Project Description Historically, monitor toxins periodically during significant blue-green algae (BGA) blooms. In the past, toxin levels have been low or nondetect. In 2015, initiated special monitoring project as: Significant increase in BGA concentrations in East Bay reservoirs Recent toxin issues in the United States (e.g., Toledo, EB Parks) New USEPA Health Advisories Project features: Focused on East Bay due to high BGA in East Bay reservoirs Targeted all 4 toxins commonly monitored Conducted biweekly monitoring over 1 year (Aug 2015 to Aug 2016) to assess occurrence & seasonality (later extended) Used ELISA method for routine tests with some split LC/MS/MS samples to contract lab 7

8 Algal Toxin Monitoring, Project Objectives Analytical Capabilities: Develop in-house laboratory capabilities for algal toxins (ELISA and eventually LC/MS/MS) Baseline: Build a baseline data set and explore correlations with phytoplankton Treatment: Evaluate SVWTP treatment of algal toxins (via bench tests and full-scale tests) Customers: Improve our knowledge on algal toxins to better respond to public inquiries Response Plan: Develop an Algal Toxin Monitoring & Response Plan Calaveras Reservoir 8

9 Algal Toxin Results by ELISA, /17/15 to 10/30/17 Location Total Microcystins (ug/l) Cylindrospermopsin (ug/l) Anatoxin-a (ug/l) Saxitoxin (ug/l) Calaveras Reservoir ND (<0.15) to 6.9 (number of samples) n=70 SVWTP Raw, Calaveras ND to 0.5 n=10 San Antonio Reservoir all ND all ND (<0.05) n=57 all ND (<10/<0.165) n=55 mainly ND (<0.022) with a few trace detections in both reservoirs near DL (far below health advisories) n=29 n=54 SVWTP Raw, San Antonio all ND n=16 SVWTP Effluent all ND all ND all ND all ND ND = Not Detected n=21 n=9 n=6 n=7 9

10 Microcystins at Calaveras Reservoir (surface) Monthly Maximums, 8/17/15 to 10/30/17 All results by ELISA 10

11 Calaveras Reservoir - 10/13/2015 Post-algaecide Post-turnover Total MC (surface) = 1.9 ug/l Phytoplankton = 60 million NU/m3 (86% BGA) Secchi depth = 6.5 feet Surface film/scum 11

12 Microcystins Pre & Post Algaecide/Turnover Calaveras Reservoir, Sept/Oct

13 Limnology Probes & Kemmerer Sampler Calaveras Reservoir (8/31/15, 11:30 a.m.) Phytoplankton: count=89 million NU/m3, 97% BGA ~MC peak=10 feet ~adit depth=30 feet (plant OOS, 8/31) ~reservoir bottom=70 feet 13

14 Phytoplankton Correlations 27-month correlations between total microcystin levels and blue-green algae concentrations by genus, August 17, 2015 to October 30, 2017 BGA Genus Peak Plankton (NU/mL)* R 2 ** Aphanizomenon Oscillatoria Anabaena Microcystis Aphanocapsa Lyngbya Coelosphaerium Total Phytoplankton Notes *NU/mL = million NU/m3 **Total MC vs. phytoplankton count (linear regression coefficient) Co-occurrence - 8/17/15 to 10/30/17 Of 34 total microcystins detections (Calaveras surface samples), o Microcystis detected 31 times: 31 of 34 (91%) o Aphanocapsa detected 18 times: 18 of 34 (53%) 14

15 Phytoplankton Correlations Total Microcystins and Total Phytoplankton Calaveras Reservoir 15

16 Phytoplankton Correlations Total Microcystins (toxin) and Microcystis (BGA) Calaveras Reservoir 16

17 General Treatment Goals for Algal Toxins per Literature Goal #1: Try to keep toxins within cells (intracellular) and remove with sedimentation and filtration o Monitor reservoirs for intra/extracellular fractions o Reduce or cease pre-chlorination to prevent lysing Goal #2: Apply free Cl2 at an optimal ph (<8 for MC) Goal #3: Meet CT requirement for toxin from AWWA calculator CyanoTOX 17

18 Algal Toxin Findings Aug 2015 to Oct 2017 Calaveras Reservoir Total microcystins in Calaveras surface samples were measured up to 6.9 ug/l in late September Microcystis, and possibly Aphanocapsa, are the most likely sources of microcystin production. Anabaena, the source of elevated geosmin, did not appear to be contributing to toxin levels. Other toxins were non-detect or near detection level, far below health advisories. San Antonio Reservoir To date, all toxins have been non-detect or near detection level, far below health advisories. SVWTP SVWTP easily removed low microcystin levels. All SVWTP effluent samples have been non-detect. Bench tests supported 3 recommended treatment goals: 1. Keep toxins within cells for removal by sed./filtration, 2. Free chlorinate at an optimal ph (<8 for microcystins) after filtration, and 3. Meet recommended CT target for toxin 18

19 Algal Toxin Findings Aug 2015 to Oct 2017 Monitoring & Assessment Tools ELISA kits are an effective tool for quick and inexpensive toxin screening. ELISA total microcystin measurements can be directly compared to USEPA Health Advisory (not the case for LC/MS/MS). Using ELISA and LC/MS/MS is desirable, especially when toxin levels are high, as two methods provide different benefits and help confirm detections. Profiles (e.g., chlorophyll a & phycocyanin) provide valuable information on the vertical distribution of algae. Phytoplankton identification/quantification can be used for toxin correlations and early toxin warnings. AWWA CyanoTOX calculator predicted bench test results, and can be used for future oxidation assessments. 19

20 Algal Toxin Monitoring and Response Plan, Source Waters Monitor Calaveras Reservoir (surface, CIS) and San Antonio Reservoir (surface, CIS) for: Microcystins during routine plankton tows (typically biweekly or monthly) Other toxins (Cyl, Ana, Saxi) quarterly Monitor other source waters as needed NO Elevated toxins? (any toxin > 5 ug/l) YES Implement Source Water Response Measures for Toxin(s) Source Water Monitoring Increase monitoring frequency to weekly Conduct reservoir profile Source Water Management Evaluate best adit depth Take precautions with algaecide only use algaecide at reservoir if toxins are mainly extracellular or if reservoir can be taken offline for toxin degradation monitoring 20

21 Algal Toxin Monitoring and Response Plan, NO NO SVWTP Raw Monitor SVWTP Raw for: Microcystins biweekly Other toxins (Cyl, Ana, Saxi) quarterly SVWTP Raw toxin > 1 ug/l? YES SVWTP Response Measures Plant Monitoring Increase monitoring frequency at SVWTP Raw and SVWTP effluent (TWR Eff) to: Weekly if toxin is 1 to 5 ug/l in SVWTP Raw 3X/week if toxin > 5 ug/l in SVWTP Raw Daily if toxin detected in SVWTP TWR Eff Conduct SVWTP profiles to assess treatment unit performance Switch source waters or use blending YES Alternative source water available? NO Implement SVWTP Response Measures Plant Optimization Consider reduction or elimination of pre-chlorination to prevent cell lysing Use powdered activated carbon (PAC), if available Maintain ph < 8 in Chlorine Contact Tank (CCT) Consider increasing Cl2 in CCT by 0.5 to 1.0 mg/l, and meet CT oxidation target for toxin per AWWA calculator CyanoTOX Monitor recycled wash water for toxins 21

22 Algal Toxin Monitoring and Response Plan, SVWTP effluent (TWR Eff) Monitor TWR Eff for: Microcystins biweekly (paired with raw) Other toxins (Cyl, Ana, Saxi) quarterly NO TWR Eff toxin >DL? TWR Eff toxin >HA? NO YES YES Switch source waters or use blending YES Alternative source water available? Conduct confirmation sampling at multiple locations NO Implement daily sampling and plant optimization NO SFRWS finished water > HA? YES Notify SWRCB and assess need for public and wholesale notifications 22

23 Next Steps for Algal Toxins Implement Monitoring and Response Plan, Re-assess 2-year plan in 2019, and revise as needed Continue to track literature and new algal toxin technologies San Antonio Reservoir 23

24 Questions? contact information Gregg Olson, P.E. Associate Engineer (650) SVWTP 24