Evaluating Treatment Techniques for Algal Toxins

Warren HenryCity of Toledo

Nick Burns Black & Veatch

Agenda• Background on algal toxins• Concerns• Treatment Effectiveness

• Toledo Experience • Summary

2

Lake Erie, 2011

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

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

Treatment Effectiveness

Treatment of Algal Toxins in Rivers and River Influenced Groundwater (WaterRF Report 4526)

Black & VeatchTailored 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

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

Intracellular Contaminants(Removal of Intact Cells)

(Westrick, et al. 2010) (Newcombe, House, et al. 2010)(G. Newcombe 2009) 7

Treatment Expected Removal Comments

Coagulation / Flocculation,Clarification [Sedimentation or DAF],Lime precipitation, Rapid Sand Filtration

> 99.5% Sludge must be regularly removed and filters frequently backwashed to avoid cell lysis.

Microfiltration & Ultrafiltration > 98% Frequent backwash required to avoid cell accumulation.

Slow Sand & Riverbank Filtration > 99% Frequent backwashing required for filters to avoid cell accumulation.

Pre-oxidation Not Recommended

Can lead to cell lysis and release of intracellular toxins.

Removal of Extracellular Toxins• Physical:

• Adsorption: GAC and PAC.• Membranes: NF/RO.• Biological.

• Oxidation:• Chlorine.• Ozone.• Chlorine dioxide.• Chloramines.• Potassium permanganate.• Advanced oxidation.

8

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).

*WaterRF Report 4526 9

00.10.20.30.40.50.60.70.80.9

1

0 20 40 60

C/Co

PAC Dose (mg/L)

MC-LRMIBGeosmin

Free Chlorine General Recommendations

*G. Newcombe, 2009 10

pH < 8Residual after 30 minutes (mg/L) > 0.5Chlorine dose (mg/L) > 3CT (mg-min/L) 20

Expected Reduction

MCs 100%(a)

CYN 100%ANTX-a NA(b)

STXs 70%(a)For more susceptible MCs(b)NA: Not applicable - not susceptible to chlorination

Free Chlorine

• Effective for MC-LR removal:• 100% removal at pH less than 8.0.• Hypochlorous acid species.

• Virtually no removal at pH 10.5.

• Disinfection byproduct considerations.

• Chloramines are ineffective.

*WaterRF Report 4526 11

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4

C/Co

Chlorine Dose (mg/L)

9.5 pH 10.0 pH

10.5 pH

Chlorine Dioxide

• ClO₂ little removal of MC-LR.

• Potential to lyse cell and release algal toxins.

• Chlorite MCL.

*WaterRF Report 4526 12

Permanganate• Effective for MC-LR

removal.• Dosage may result in

pink water.• Manganese removal

considerations.

• Solids recycle stream considerations.

*WaterRF Report 4526 13

00.10.20.30.40.50.60.70.80.9

1

0 1 2 3 4C/

CoPP Dose (mg/L)

RawElevated

Ozone

• 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 4526 14

00.10.20.30.40.50.60.70.80.9

1

0 1 2 3 4

C/Co

Ozone Dose (mg/L)

MC-LRMIBGeosmin

Utility A Full-Scale Data

• 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).

Pre-oxidation required for disinfection, but resulted in a release of algal toxins.

15

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Raw BeforePrimary

AfterPrimary

FilterInfluent

Finished

MC-

LR, p

pb

8/4/20148/5/2014

ClO2 Cl2PAC

Utility B Full-Scale Data• PAC use achieved good

reduction in algal toxin.• Dose of 4-6 mg/L

• Chlorine oxidation of toxin as well.

Low concentration event was effectively managed with multiple barriers.

16

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

MC-

LR, p

pb

8/1/2014

8/2/2014

8/4/2014

PAC Cl2

Toledo Experience

17

Toledo: Collins Park Water Treatment Plant

Algae Toxins Prompt Toledo to issue public notice in August 2014.18

Collins Park WTP Intake

Collins Park Water Treatment Plant

19

Microcystin-LR Levels, August 2014

Raw water concentration far exceeded safe levels although plant effluent was generally low.

20

Health Advisory

Project Approach

• 3 years water quality review (2013-2015).

• Immediate improvements.• Permanganate feed improvements.• PAC improvements at raw water pump station. • PAC addition into 3rd pass flocculation zone.

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- 6.5 mg/L KMnO4 required

- Up to 40 mg/L PAC at LSPS

- 3 mg/L max PAC at WTP• Long range strategy:

• Existing PAC and permanganate.• Raw or intermediate ozone.• Post-filtration GAC adsorption contactors.

Post-Filtration Adsorption

• Lignite outperformed others.

• 10 min EBCT.

• Bypass during non-HAB season.

• Replacement every 2 years.

Engineer’s Opinion of Project Cost ~ $100MAnnual Operating Cost of ~$4.5M

22

Coconut

Bituminous

WoodLignite

Bench-scale Microcystin Ozonation Results

All ozone dosages resulted in high levels of microcystin oxidation.

Location Raw Settled

pH 8.2 9.7

Ozone Dosage 1 2 3 1 2 3

Raw Microcystin-LR, ug/L 36 20

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 0.5 1.2 2.1 0.3 0.9 1.3

CT (10 min), mg/L-min 0.8 3.7 10.4 0.3 0.8 1.3

Giardia Inactivation, logs 4.8 21 60 1.4 4.5 7.2¹Analytical detection limit = 0.10 ug/L

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Intermediate Ozonation

• Lower ozone dose.

• Bromate managed.

• Fewer solids.

• Continued PAC and KMnO₄ use in raw water pipeline.

Engineer’s Opinion of Project Cost ~ $40MAnnual Operating Cost of ~$0.3M

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Take Home Messages

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Conclusions• Algal toxins are a growing

concern.• Effective and practical

microcystin removal processes:• PAC• Ozone• Permanganate• Free chlorine (at pH < 9.0)

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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.

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Acknowledgements• City of Toledo

• Ed Moore• Patekka Bannister• Andy McClure

• Black & Veatch Team• David Vallejo• Dianne Sumego• Bob Harbron• Jeff Neemann• Bob Hulsey

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• Arcadis

• Water Research Foundation• Report 4526 - 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.

Nick BurnsDirector of Water Treatment TechnologyBlack & VeatchBurnsNL@BV.com469-513-3205

18 October 2017

Thank You

&Warren HenryWater Program ManagerCity of ToledoWarren.Henry@toledo.oh.gov419-245-1840