Risk Assessment Approach to Protecting Industrial Assets from

Macrofouling and Control Strategies Used in North America

Renata Claudi MSc. RNT Consulting Inc.

Zebra and Quagga MusselsDreissenid family

Zebra mussel1988

Map: New York Sea Grant

How do they move around

• Downstream in interconnected waterways• Recreational boating• Aquaculture transfers• Aquarium and Pet Trade• Live bait• Live food releases• Canals and Waterways

Risks Posed to Industrial Facilities by Mussel Fouling – Reason for Mitigation

• Decreased flow

• Potential plugging of essential components/systems

• Increased corrosion

Mitigation – Step IReview environmental conditions

• Review environmental conditions of the river/lake/reservoir from which water is drawn

• Based on various parameters prediction on severity of infestation can be made

• If one of the critical parameters is approaching “marginal” conditions for survival, it may offer mitigation opportunity

Parameter None Little Moderate High

Calcium mg/L <10 <16 16-24 ≥24

Alkalinity mg CaCO3/L <35 35-45 45-89 >90

Total Hardness mg CaCO3/L <40 40-44 45-90 ≥90

pH <7.2 7.2-7.5 7.5-8.0 or 8.7-9.0 8.0-8.6

Mean Summer Temperature oC <18 >28 18-20 20-22 or 25-28 22-24

Dissolved Oxygen mg/L (% saturation) <6 (25%) 6-7 (25-50%) 7-8 (50-75%) ≥8 (>75%)

Conductivity μS/cm <30 <30-37 37-84 ≥85

Salinity mg/L (ppt) >10 8-10 (<0.01) 5-10 (0.005-0.01) <5 (<0.005)

Secchi depth m <0.1 0.1-0.2 or >2.5 0.2-0.4 0.4-2.5

Chlorophyll a μ/L <2.5 or >25 2.0-2.5 or 20-25 8-20 2.5-8

Total phosphorous μg/L <5 or >35 5-10 or 30-35 15-30 10-15

Total Nitrogen μg/L <200 200-250 250-300 300-500

Example of Parameters vs. Infestation Table for Dreissena bugensis

Mitigation – Step 2Review facility to be protected

- examine drawings of all cooling water system

- physically walk the facility to verify drawings and observe materials of construction

- verify mode of operation, duty cycle, inspection schedule and monitoring efforts

Systems at Risk

• All external structures and internal piping exposed to raw water which contains, mussel veligers and/or adults. The flows have to be over 6ft/s, continuously, for settlement not to occur.

• Water intake structures

• Aquaducts

• Cooling water systems

• Fire protection systems

• Any instrument using raw water

• Civil structures (bridges, buoys etc.)

Water Intake Structures -Mechanisms of Fouling

• Settlement of veligers during the breeding season, if flow velocities are less then 6ft/s. Large volumes of water passing through the intake structure insure large number of veligers come into contact with all available surfaces.

• Migration of adults from surrounding areas onto the intake structure, probably year around

Impacts

• Loss of flow through settlement, initially due to increased coefficient of friction, later due to volume restriction

• Shell debris collecting in low lift wells, pump wells or forebays

• Fouling of stop log gains, difficulties in isolating pump wells and level control

• Plugging of trash racks and other fixed screens

Cooling Water System -Mechanisms of Fouling

• Ingress of adults individuals or clumps (year around) if no strainer is in place past the pumps. The source may be any external surface including the pump itself.

• Ingress of veligers during the breeding season • provided the flow velocities in the system are less

then 6ft/s to allow settling.

Risk to Cooling Water Systems

• Decrease in system pipe diameter & flow due to mussel settlement

• Plugging of heat exchangers with clumps or individual shells; loss of cooling

• Partial plugging of heat exchangers may lead to uneven flow velocities in the heat exchanger as well as silt build up. These conditions could result in pipe abrasion and erosion.

• Blockage of system valves (in open or shut position. Fouling of valve seat can lead to improper operation.

• Blockage of building drains and fouling of sumps

Heat Exchanger Fouling

Heat Exchanger plugged by shell debris from upstream

Fire Protection System - Mechanisms of Fouling

• Generally FP systems are stagnant, unless tested. Stagnant system should have dissolved oxygen levels low enough not to allow mussels to survive (below 3mg/L). In practice, most draw quantities of make-up water.

• In addition, if no strainers are present make-up pumps or dedicated fire pumps can introduce adult mussels or shell debris into the FP system.

Risk to Fire Protection Systems

• Main Fire System Pump

• Deluge strainers

• Sprinkler Nozzles• Fire Hose Nozzles• Fire Hydrants

Risks to Instrumentation

Any instrument in contact with raw water should be evaluated

Thrust Bearing Sight Glass

Level gauges

Civil Structures At Risk

• Municipal Fire Hydrants• Irrigation Systems• Recharge Areas• Shipping and Navigational Buoys• Locks and Dams• Bridge Footings in Water

Additional Risk- Macrofouling by Mussels Can Enhance Metal Corrosion by;

• Mechanical Damage• Exposure of fresh surfaces to corrosive

factors• Production of feces and pseudofeces

which in turn support microorganisms

Mitigation – Step 3Minimizing mussel fouling

• Proactive

Does not allow growth of mussels in the system or on the surface protected

• Reactive

Does allow mussels to grow in the system or on the surface. Established populations have to be eliminated periodically

Options for External Structures*

*Structures That Are in Direct Contact With the External

Environment; No Isolation Is Possible

Reactive Options for External Structures

Mechanical Cleaning

• de-water and use powerwash• underwater, scrape and vacuum or

powerwash

Proactive Options for External Structures

• Antifouling Coatings - for both steel and concrete

• Non-toxic, soft silicone barrier coatings• Toxic, copper/zinc based coatings

(ablative and non-ablative) – EPA approval required

• Life-span 5-7 years before topcoat needs to be refreshed

Coatings

• Number of new formulations on the market in response to the ban of tributyl tin coatings in the marine industry

• Given the cost ( $10 - $40/sq.ft) and the extensive surface preparation required, ask for multiyear performance data

• Many coatings fail after 12 to 18 months• Surface preparation is onerous but

essential

Copper/Beryllium after 2 years

•

Bioclean Silicone after 4 years

Coatings

• Vendors with known successful antifouling coatings- CPM Coatings/ Chugoku PaintBioclean - Si

- Kansai Paint (Biox Si)- International Paints (Intersleek)- GE Coatings (Exsil)

Options for Internal Piping Systems

Reactive Options for Internal Piping Systems

• Thermal Wash - 32oC for 48 hours (90o F)40oC for 1 hour (104o F)

Thermal Spray - 80oC for 5 seconds60oC for 10 seconds

• Mechanical Cleaning - scrape large diameter pipes - use expanding air bubbles ?? or remote vehicle tools

on difficult areas• Flushing with weak acids• Oxygen Deprivation

Reactive Options for Internal Piping Systems

• Non-oxidizing chemical treatment -proprietary chemicals, most of which have to be de-toxified on discharge

(12 -36 hour treatment)

Oxidizing chemical treatment- chlorine, bromine, chlorine dioxide,chloramines, ozone, potassium permanganate

(10 days + treatment at approx.1ppm)

Oxidizing Chemical Options

• chlorine• bromine• chlorine dioxide• chloramines• ozone• potassium permanganate

Oxidizing Chemical - Reactive Treatment

• None are proprietary chemicals

• Length of treatment tends to be temperature dependent. Up to two weeks of treatment may be required. Local conditions and specific tolerance of each species has to be determined

Bacterial Product - Reactive Treatment

Chemical substance produced by Pseudomonas fluorescence bacteria. This species is commonly present in soilSpecific strain developed by Dr.Dan Malloy in the U.S.This strain when present in high enough concentration causes mortality in the Dreissenid mussels.No mortality observed in any native mussels or clams of North AmericaCurrently being commercialized by Marrone Organic Innovations from CaliforniaPotential for this to be a preventative treatment

Proactive Options for Internal Piping Systems

• Sand/media filtration - has to remove all particles greater then 40 micron

• Mechanical filtration - has to remove all particles greater than ready to settle veligers. Actual mesh size is dependent on the application and industry using the filter.

Environmental Criteria affecting the performance of the filter

• Total suspended solids (TSS) load in the in-coming water

• Seasonal variation in TSS

• What is the particle size distribution of the TSS

Example of small pore self cleaning filters

49

Fine FilterChamber

Filter SiltDischarge

StrainerDrain

Filtered WaterDischarge

Main Access Hatch

InfluentRaw Water

Strainer andFilter Vent

StrainerDischarge

Access Hatches

Course StrainerChamber

Drive Unit with1/2 HP Motor

Pad Eye Pad Eye

Direction of Flow

Fine Filter Drain

Mesh RequirementsSquare Weave Mesh is Essential

Robust Support of the Mesh is Critical

Mechanical filtration test

• Installed at Nanticoke TGS, Lake Erie• 760 l/s (12000 usgpm)• 40 micron mesh• Automatic• backwash

Proactive Options for Internal Piping Systems -

UV

Environmental Criteria affecting the performance of UV

• How well does your raw water transmit UV (various factors such as colour, hardness, presence of iron and total suspended solids)

• Seasonal variation in above factors

56

In pipe UV Installation

Access to Lamps(Both ends of chamber) Electrical Junction Box

(wiring from cabinets) Upstream Isolation Valve (Not visible)

Downstream Isolation Valve

UV Monitor Access HatchAir Release

Wiper Motor Housing

Direction of Flow

5

Open channel UV InstallationUV Host Site: Bruce 5-8 CSW900 l/s (15,000 usgpm)20 hi-intensity,medium pressure lamps

SamplePoint

SamplePoint

UV Lights

5

UV Light Bank for open channel

Proactive Use of Oxidizing Chemicals for Protection of Internal Piping

Systems

• Low levels of the chemical are added continuously or semi-continuously throughout the mussel breeding season to prevent settling by creating a hostile environment.

Proactive Use of Ozone at Ontario Power Generation

• Continuous ozone addition system installed at Lennox TGS, Lake Erie

• 03mg/L added continuously during breeding season

Start-up: September 2000

Proactive Use of Ozone at Ontario Power Generation

• Intermittent ozone addition system installed in Bruce 1-4 CWS

• 600 l/s (9500 usgpm)• 2 kg/day ozone• 1 kg injected for 5 minutes, 2 times/day• manufacturer - Mitsubishi

Start-up: October 2000

Proactive Use of Chlorine at Ontario Power Generation

• Continuously at 0.3 - 0.5ppm TRC (at the end of the treated system)

• Semi-continuously at 0.3 - 0.5ppm TRC (at the end of the treated system). Most often used regime, 15 minute on 90 minutes off.

Proactive Use of Chlorine at Ontario Power Generation

• Regulatory limit is 10ppb TRC in the combined discharge.

• Regulatory objective is 2ppb .

Closed Loop Cooling

- Choose cooling heat sink (air or water)- Does not necessarily address all

challenges- Space considerations- Piping layout changes and constructability

Suggestions for Control • Rapid Response Option (if settlement

and shell transport increases dramatically and suddenly):– Install portable chlorine skids to protect

critical areas– Use thermal treatment where possible– Use weak acids to dissolve shells and

corrosion products– Mechanical cleaning as system

performance deteriorates.

Suggestions for Control – Long Term• Determine your vulnerability (Proactive/Reactive)• Use thermal treatment where possible• Use coatings to minimize need for mechanical

cleaning• Protect piping from shell debris by installing self

cleaning strainers• If possible follow strainers with self cleaning small

pore filters or UV• Use chemicals as necessary• Investigate Marrone Organic Innovations Product