2014 Ontario Water Works Conference May 4-7 th, 2014 London, Ontario. Methods for evaluating pathogen log removal in a water treatment plant

Transcription

1 2014 Ontario Water Works Conference May 4-7 th, 2014 London, Ontario Methods for evaluating pathogen log removal in a water treatment plant Andy Campbell 1 Ian Douglas 1,2 Josh Elliott 1,2 Monica Emelko 3 Nicole McLellan 3,4 A. Banihashemi 3 1 City of Ottawa 2 University of Toronto 3 University of Waterloo 4 Stantec Consulting Ltd.

2 Water Quality / Research Team Erin Penny Josh Andy Ian Gwyn N.McLellan A. Banihashemi Dr.M.Emelko.

3 Log removals not a requirement Better understanding of plant performance Validate credits granted Learn how various pathogens are removed Weak points in your multiple barriers Fundamental to QMRA Best practice Public health

4 Tools & techniques to evaluate pathogen removal in a water treatment plant 1. Regulatory tables & guidance 2. Research Literature 3. Particle counts & turbidity 4. Native organisms 5. Pathogen challenge studies (pilot plant) 6. Microsphere & surrogate spiking (full-scale)

5 Method #1 Use of regulatory guidance values for pathogen removal

6 Regulatory tables state pathogen removal credits for various treatment processes Procedure for disinfection of drinking water in Ontario (Ministry of Environment, 2006) Treatment Crypto log removal credit Giardia log removal credit Virus log removal credit Conventional filtration Direct filtration Slow sand filtration Diatomaceous earth filtration Membrane filtration Cartridge filtration

7 Method #2 Research literature values for various treatment processes

8 Method #2 Research literature values for various treatment processes KWR (2010) review of published literature values from various pilot & full-scale plant studies evaluated the quality of each study (level 1-5) and reported weighted-mean values for log-removal tables of reported log-removal values for cryptosporidium giardia bacteria spores Viruses treatment processes: coagulation & sedimentation conventional filtration rapid granular filtration slow-sand filtration GAC filtration direct filtration

9 Method 2: Example: literature reported values for log-removal by conventional treatment (KWR, 2010) Study # Crypto Giardia Virus Bacteria B.spores Ministry of Environment log removal credit Health Canada log removal credit Wt. Avg (Std.dev) (1.3) (0.9) (1.4) (0.8) (0.9)

10 Method #3 Use of particle counts and turbidity data

11 Method #3 Use of particle counts and turbidity data Raw water # of particles > 2um /ml Coagulation transforms the entire particle matrix therefore, not comparing the same particles! 1 0 1/Jan 20/Feb 11/Apr 31/May 20/Jul 8/Sep 28/Oct 17/Dec Filter effluent average particle log removal = 3.6

12 Method #4 Use of native organisms to assess removal through treatment

13 Water Treatment Process City of Ottawa Britannia & Lemieux Island WPP s Total coliforms E.Coli Aerobic spores Cl 2 Cl 2 NH 3 NaOH HFS Anthracite Raw water Coagulation & Flocculation log removal for coag + sed Sedimentation Sand Dual-media Filtration CT Disinfection (Clearwell) ph Adjustment & Chemical Mixing log removal for coag + sed + filtration

14 Water Treatment Process City of Ottawa Britannia & Lemieux Island WPP s 10 4 Total coliforms per 100 ml 10 3 Total coliforms per 100 ml 1 Total coliform per 100 ml Anthracite Sand Raw water Coagulation & Flocculation Log removal = -Log 10 (C i /C o ) Sedimentation Dual-media Filtration log removal for coag + sed = 1 log log removal for coag + sed + filtration = 4 log

15 COAG / FLOC / SEDIMENTATION Ottawa Full-scale physical log-removal of native Total Coliform and E.coli microorganisms ( ) Frequency Total Coliform log removal n=365, mean = 1.78, stdev = 0.51 Frequency E.coli log removal n=258, mean = 1.40, stdev =0.34 Log removal Log removal

16 Method #4 Use of native organisms to assess removal through treatment

17 Method #5 Pilot-scale seeding trials using microorganisms and surrogate particles fluorescent e.coli giardia crypto 4.5 µm sphere

18 Pilot Plant Water Treatment Process Anthracite Sand Raw water Coagulation & Flocculation Sedimentation Dual-media Filtration

19 Feed locations for Pilot Plant experiments Expt #4,5 & 8: raw water spiking (bio-colloids) Alum + H2SO4 Activated SiO 2 Expt #3,6 & 7: filter spiking (bio-colloids) Anthracite Sand Raw Water Coagulation & Flocculation Sedimentation Dual-media Filtration Have the flexibility to measure removals through both co-ag and filtration independently

20 Pilot Plant experiments Trial #3 Filter spiking cold water Trial #5 Raw spiking cold water Trial #7 variable seed concentrations Apr-12 Jun-12 Aug-12 Oct-12 Dec-12 Mar-13 May-13 Jul-13 Aug-13 Oct-13 Dec-13 Feb-14 Mar-14 Trial #4 Raw spiking warm water Trial #6 Filter spiking warm water Trial #8 winter challenge trial

21 Experimental methodology Pathogen surrogate virus (PRD1 bacteriophage) bacteria (polystyrene microsphere) bacteria (fluorescent E. Coli) bacteria / protozoa (Aerobic Spores - B. Atropheus) cryptosporidium (polystyrene microsphere) cryptosporidium (Cryptosporidium oocysts) Size (µm) Concentration (# per L) x x x x x x 10 6

22 Removal performance of coag/floc/sed vs. filtration PRD1 1.0 µm E.coli Spores 4.5 µm Crypto

23 Removal performance of coag/floc/sed vs. filtration 6.00 coag/sed 5.00 filtration PRD1 1.0 µm E.coli Spores 4.5 µm Crypto

24 Experimental methodology Pathogen surrogate virus (PRD1 bacteriophage) bacteria (polystyrene microsphere) bacteria (fluorescent E. Coli) bacteria / protozoa (Aerobic Spores - B. Atropheus) cryptosporidium (polystyrene microsphere) cryptosporidium (Cryptosporidium oocysts) Size (µm) Concentration (# per L) x x x x x x 10 6 Question: Does spiking such high numbers bias the results?

25 Exp. #7 Variable seed concentration Only crypto and 4.5 µm spheres used Optimal alum/ph/silicate High filter flow rate Cold water conditions Experiment conducted in duplicate over two days Low 10 per L Medium 10 5 per L High 10 8 per L

26 Exp. #7 Variable seed concentration Log Removals - Day 1 Log Removals - Day n/a n/a Crypto log removal Crypto 4.5 µm Spheres 4.5µm MS log removal Low Seed Conc. Mid Seed Conc. High Seed Conc. 1 0 n/a n/a Crypto log removal Crypto 4.5 µm Spheres 4.5µm MS log removal Low Seed Conc. Mid Seed Conc. High Seed Conc. Answer: Apparently not

27 Method #5 Pilot-scale seeding trials using microorganisms and surrogate particles fluorescent e.coli giardia crypto 4.5 µm sphere

28 Method #6 Full-scale seeding trials using surrogate particles

29 Full-Scale seeding trials using microspheres to estimate log-removal through filtration pump 200 L 10 ML/d 2.5 x µm spheres 1.4 x µm spheres Seeding time = minutes 1000 L

30 Method #6 Full-scale seeding trials using surrogate particles micron Spheres per Litre 4.5 micron Spheres per Litre µm sphere conc. (#/L) Seeding Period 4.5 µm spheres = 4.6-log removal 1.5 µm spheres = 1.7-log removal µm sphere conc. (#/L)

31 Method #6 Full-scale seeding trials using surrogate particles

32 Next steps 1) Update our QMRA analysis (Quantitative Microbial Risk Assessment) to evaluate process risks, operational triggers, and evaluate need for UV 2) Process upsets & challenge conditions 3) Filter operations 4) Full-scale filter seeding trials (steady-state) with improved detection methods

33 Conclusion 1. Know your source water! 2. Know your treatment barriers! 3. Regulatory values/ literature values may not reflect pathogen removals at your treatment plant 4. Be careful using particle counts/turbidity to determine logremoval 5. Consider process variation & extreme events (upsets) 6. Be careful not to create other treatment risks in an effort to improve filter log removals

34 Thank you & Questions