Removing Algal Toxins from the Toledo Tap

Transcription

1 Removing Algal Toxins from the Toledo Tap Warren Henry City of Toledo Nick Burns Black & Veatch

2 Agenda Lake Erie, 2011 Background on algal toxins Concerns Treatment Effectiveness Toledo Experience Summary 2

3 Harmful Impacts Taste & odor compounds: Customer complaints. Question safety of potable supply. Algal toxins: Produce extremely dangerous toxins that can sicken or kill people and animals. Create dead zones in the water. Raise treatment costs for drinking water. Hurt industries that depend on clean water. Damaging to public confidence. 3

4 Treatment Goals/Regulations Taste & Odor: Goal to < 5 ng/l Algal Toxins: No MCL. Microcystin Health Advisory of 0.3 ug/l for sensitive populations (1.6 ug/l adults). Cylindrospermopsin Health Advisory 0.7 ug/l for sensitive populations (3.0 ug/l adults). WHO has Microcystin 1 ug/l guideline and Cylindrospermopsin 1 ug/l. Microcystin-LR, Anatoxin-a, Cylindrospermopsin on CCL3. 4

5 Treatment Effectiveness Treatment of Algal Toxins in Rivers and River Influenced Groundwater (WaterRF Report 4526) Black & Veatch Tailored Collaboration Partners: Water District #1 of Johnson County, City of Lawrence, City of Olathe Public Works Department, City of Topeka Water Division, and State of Kansas Water Board 5

6 Intracellular vs Extracellular What is inside versus outside the algal cells. Concentrations inside and outside vary: Number of algal cells. Type of algae. Growth cycle. Dilution/volume. Oxidation can cause cell lysing: What was inside is now outside. 6

7 Intracellular Contaminants (Removal of Intact Cells) Treatment Coagulation / Flocculation, Clarification [Sedimentation or DAF], Lime precipitation, Rapid Sand Filtration Expected Removal > 99.5% Microfiltration & Ultrafiltration > 98% Slow Sand & Riverbank Filtration > 99% Pre-oxidation Not Recommended Comments Sludge must be regularly removed and filters frequently backwashed to avoid cell lysis. Frequent backwash required to avoid cell accumulation. Frequent backwashing required for filters to avoid cell accumulation. Can lead to cell lysis and release of intracellular toxins. (Westrick, et al. 2010) (Newcombe, House, et al. 2010) (G. Newcombe 2009) 7

8 Removal of Extracellular Toxins Physical: Adsorption: GAC and PAC. Membranes: NF/RO. Biological. Oxidation: Chlorine. Ozone. Chlorine dioxide. Chloramines. Potassium permanganate. Advanced oxidation. 8

9 Powdered Activated Carbon Effective for all algal toxin removal. Generally high dosages ~ 20 mg/l. Long contact times are desirable. Solids production and disposal. GAC also effective (if adsorptive capacity remaining). C/Co MC-LR MIB Geosmin PAC Dose (mg/l) *WaterRF Report

10 Free Chlorine General Recommendations ph < 8 Residual after 30 minutes (mg/l) > 0.5 Chlorine dose (mg/l) > 3 CT (mg-min/l) 20 MCs 100% (a) Expected Reduction (a) For more susceptible MCs (b) NA: Not applicable - not susceptible to chlorination CYN 100% ANTX-a NA (b) STXs 70% *G. Newcombe,

11 Free Chlorine C/Co ph 10.0 ph 10.5 ph Effective for MC-LR removal: 100% removal at ph less than 8.0. Hypochlorous acid species. Virtually no removal at ph Disinfection byproduct considerations Chlorine Dose (mg/l) Chloramines are ineffective. *WaterRF Report

12 Chlorine Dioxide ClO₂ little removal of MC-LR. Potential to lyse cell and release algal toxins. Chlorite MCL. *WaterRF Report

13 Permanganate Effective for MC-LR removal. Dosage may result in pink water. Manganese removal considerations. Solids recycle stream considerations. C/Co Raw Elevated PP Dose (mg/l) *WaterRF Report

14 Ozone C/Co MC-LR MIB Geosmin Ozone Dose (mg/l) Effective for MC-LR removal. Removal to non-detectable levels at doses less than demand. Effective for other contaminants as well: Taste & odor causing compounds. *WaterRF Report

15 Utility A Full-Scale Data MC-LR, ppb ClO 2 PAC Cl 2 8/4/2014 8/5/2014 Pre-oxidation releases intracellular toxin. Pre-oxidation used to meet disinfection requirements. Some reduction with PAC (10 mg/l) More reduction with chlorine (ph 9.0). 0 Raw Before Primary After Primary Filter Influent Finished Pre-oxidation required for disinfection, but resulted in a release of algal toxins. 15

16 Utility B Full-Scale Data 0.9 PAC Cl 2 PAC use achieved good reduction in algal toxin. Dose of 4-6 mg/l Chlorine oxidation of toxin as well. MC-LR, ppb /1/2014 8/2/2014 8/4/ Low concentration event was effectively managed with multiple barriers

17 WHICH OXIDANTS ARE EFFECTIVE? Microcystin Anatoxin-a Cylindrospermopsin Saxitoxin Chlorine Yes No Yes Yes Ozone Yes Yes Yes No Chloramine No No No Need data Chlorine Dioxide No No No Need data Advanced oxidation Yes Yes Yes Need data Permanganate Yes Yes No No OXIDATION Adapted from Westerick et al

18 Toledo Experience 18

19 Toledo: Collins Park Water Treatment Plant Collins Park WTP Intake Algae Toxins Prompt Toledo to issue public notice in August

20 Collins Park Water Treatment Plant 20

21 Microcystin-LR Levels, August 2014 Health Advisory Raw water concentration far exceeded safe levels although plant effluent was generally low. 21

22 Project Approach 3 years water quality review ( ). Immediate improvements. Permanganate feed improvements. PAC improvements at raw water pump station. PAC addition into 3 rd pass flocculation zone. Long range strategy: Existing PAC and permanganate. Raw or intermediate ozone. Post-filtration GAC adsorption contactors mg/l KMnO 4 required - Up to 40 mg/l PAC at LSPS - 3 mg/l max PAC at WTP 22

23 Post-Filtration Adsorption Lignite outperformed others. 10 min EBCT. Bypass during non-hab season. Replacement every 2 years. Coconut Bituminous Wood Lignite Engineer s Opinion of Project Cost ~ $100M Annual Operating Cost of ~$4.5M 23

24 Bench-scale Microcystin Ozonation Results Location Raw Settled ph Ozone Dosage Raw Microcystin-LR, ug/l Effluent Microcystin-LR, ug/l ND¹ ND ND ND ND ND Oxidation Efficiency, percent 99.7% 99.7% 99.7% 99.5% 99.5% 99.5% Initial Residual, mg/l CT (10 min), mg/l-min Giardia Inactivation, logs ¹Analytical detection limit = 0.10 ug/l All ozone dosages resulted in high levels of microcystin oxidation. 24

25 Intermediate Ozonation Lower ozone dose. Bromate managed. Fewer solids. Continued PAC and KMnO₄ use in raw water pipeline. Engineer s Opinion of Project Cost ~ $45M Annual Operating Cost of ~$0.3M 25

26 OEPA s HAB General Plan OH s new policy >1.6 µg/l MC in raw or any in drinking water triggers Treat 100 µg/l of extracellular to nondetect (<0.3 µg/l) Multi-barrier approach Source avoidance/ treatment and treatment plant optimization/improvement Multi-barrier treatment within the plant best option for treatment. 26

27 Verifying Ozone s Efficiency Ozone Design: 1.8 mg/l, for 3.5 mg/l of settled TOC Bench-scale testing Natural MC Lab-grade Natural MC tests not representative of the plant. Raw water Natural w/o PAC MC Softened + Softened MC Spiked Ozonated 1-2 µg/l MC TOC: 5.36 mg/l 145 µg/l MC ELISA (45 µg/l MC-LR) TOC: 28.7 mg/l 86 µg/l MC (MC-LR) 50 µg/l MC ELISA (40 µg/l MC-LR) TOC: mg/l (higher (80 th than Percentile the max of seen in last 17 years in settled water) historically seen TOC at settled water) 1 mg/l of O 3 : <0.1 µg/l (MC-LR) 2 mg/l of O 3 : 18 µg/l ELISA (13 µg/l MC-LR) 32 mg/l of of O 3 : O25 3 : µg/l <0.1 ELISA µg/l (13 (MC-LR) µg/l MC-LR) 6 mg/l of O 3 : 1.0µg/L ELISA (0.16 µg/l MC-LR) 3 mg/l of O 3 : <0.1 µg/l (MC-LR) Even 1 mg/l treated 86 µg/l within the plant. 27

28 COT s HAB General Plan 100 Multi-barrier approach Need to achieve ~99.97% removal One treatment alone can t get there Optimization of current treatment PAC dose increase Filter operation changes Chlorine dose increase Implementation of ozone MC Concentration Removed by each Disinfection Segment (µg/l) PAC Removed 42.0 µg/l (42% Removal) Ozone Removed 57.4 µg/l (99% Removal) Chlorine Removed 0.32 µg/l (55% Removal) Chlorine Removed 0.17 µg/l (97.1 % Removal) PAC Removed 82.0 µg/l (82% Removal) Ozone Removed 17.8 µg/l (99% Removal) Ozone needed, along with other treatment, to achieve goal. 0 Average MC Remaining 0.26 µg/l Chlorine Ozone PAC Maximum MC Remaining µg/l 28

29 Ozone Generation & Process Application 29

30 Toledo Ozone Generation Room 1200 ppd generators Continuous or seasonal operation Hazard occupancy Expandable through knockout wall Sized for peak operations 30

31 Toledo Ozone Contactor Basin Contact time varies for application (approx 10 mins) 31

32 Project Summary 32

33 Schedule of Completion Dec. 2014: Bench-scale screening June 2015: Preliminary Design Report Jan 2017: Start design May 2018: Final design complete May-September 2018: Construction contract bid and award August 2020: Ozone System Substantial Completion February 2021: Final completion 33

34 Estimated Project Costs 90% Predicted project cost: $46.4 million Ozone Equipment: ~$6.3 million Process Equipment: ~$12.7 million Site Improvements: ~$3 million Cast in place concrete: ~$6.8 million (With installation, without markups) 34

35 Take Home Messages 35

36 Conclusions Algal toxins are a growing concern. Effective and practical microcystin removal processes: PAC Ozone Permanganate Free chlorine (at ph < 9.0) 36

37 Conclusions Consider multiple barriers. Utility action: Develop a response plan. Determine analytical methods. Perform bench-tests. Methodology for balancing multiple barriers. Document full-scale performance. 37

38 Acknowledgements City of Toledo Ed Moore Patekka Bannister Andy McClure Black & Veatch Team David Vallejo Dianne Sumego Bob Harbron Jeff Neemann Bob Hulsey Arcadis Water Research Foundation Report Treatment of Algal Toxins in Rivers and River Influenced Groundwater. Tailored collaboration partners: Water District #1 of Johnson County, City of Lawrence, City of Olathe Public Works Department, City of Topeka Water Division, and State of Kansas Water Board. 38

39 Thank You & Warren Henry Water Program Manager City of Toledo Nick Burns Director of Water Treatment Technology Black & Veatch April 2018