General Types of Counter‐Flow Fill - ChemTreatdev.chemtreat.com/wp-content/uploads/2012/12/2c-Cooling-Water... · • Use organicorganic CC forfor energyenergy && tissuetissue –

General Types of Counter‐Flow FillGeneral Types of Counter Flow Fill

Decreasing tendency to clog Decreasing tendency to clog Increasing performanceIncreasing performance

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Fill for Severe Fouling Applicationse g Contact Systemse.g. Contact Systems

Low film specific surface areaIntegral Drip Points Low film specific surface area

High droplet surface due to integral drip points

Integral Drip Points

integral drip points

Moderate performance

Excellent anti fouling Excellent anti‐fouling characteristics

Good Poor

Fouling resistance in dirty

Thermal Performance

Hybrid Trickle (H/T) water systems

Property of ChemTreat, Inc. Do not copy without permission.74

SPX – Marley Guidelines for Tower Fill Selection

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The combination of The combination of BiofoulingBiofouling,, Silt, and Oil Silt, and Oil is is severely foulingseverely fouling

Property of ChemTreat, Inc. Do not copy without permission.

Guidelines for Tower Fill Selection19mm

CF21mm

OF19mm

VF25mm

H/T

Allowed TSS w/good <100 <200 <500 <1000Allowed TSS w/good microbial control (ppm):

<100 <200 <500 <1000

Allowed TSS w/poor microbial control (ppm):

<25 <50 <200 <500

Allowed Oil & Grease None <1 <5 <50Allowed Oil & Grease concentration (ppm)

None <1 <5 <50

Allowed Fibers in water None None None None

CF – Cross FluteOF – Offset FluteVF – Vertical FluteHT – Hybrid Trickle(Brentwood Ind.Product Designations)


Biofilm DevelopmentBiofilm Development1. Organics condition

the surface2 Pioneer organisms2. Pioneer organisms

begin colonization3. Colonies grow and

diversify in bacterialdiversify in bacterial types

4. Developing into a fully formedfully formed consortia (Log growth phase)

5. Microorganisms5. Microorganisms detach release into the bulk water

B lk t “Pl kt i ” i S b t f th “S il ” i th fB lk t “Pl kt i ” i S b t f th “S il ” i th f

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Bulk water “Planktonic” organisms are a Subset of the “Sessile” organisms on the surfaceBulk water “Planktonic” organisms are a Subset of the “Sessile” organisms on the surface


MICMicrobiologically Induced Corrosion

Sessile

Microbiologically Induced Corrosion

• Planktonic“ ” “b lk

Planktonic

– “Free swimming” in “bulk water”

– Mostly aerobic• Sessile• Sessile

– Attached to a surface– Mostly anaerobic

• Sulfate Reducing Bacteria (SRB)• Sulfate Reducing Bacteria (SRB)• Convert Sulfate to corrosive Sulfide

• Acid producing bacteriaSt l i li t d i• Strongly implicated inMicrobiologically Induced Corrosion (MIC)


Need to Monitor and Control Sessile MicroorganismsNeed to Monitor and Control Sessile Microorganisms

Heat Transfer andFluid Frictional ResistanceFluid Frictional Resistance

Cooling Cooling WaterWater Flow Flow Fluid Frictional ResistanceFluid Frictional Resistance Fluid Frictional ResistanceFluid Frictional Resistance

Stagnant Boundary Layer (Mostly water)Stagnant Boundary Layer (Mostly water)2020‐‐80x Less Conductive than turbulent flow80x Less Conductive than turbulent flow

Visco‐elastic Layer Disproportionate Pressure Drop• ¾” Brass tube 10% Dia reduction 70% DP increase

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¾ Brass tube, 10% Dia. reduction 70% DP increase• U reduced 55% from 175 to 79 Btu/hr‐ft2‐°F


Biofouling Organisms• Higher life formsHigher life forms

– Protozoa– Amoeba– Ciliates

• AlgaeAlgae– Require sunlight for growth (tower deck)– Convert bicarbonate into organic carbon

• food for bacteriaF d f t d “hi h lif f ”– Food for protozoa and “higher life forms”

• Fungi– Break down complex organics

• tower wood fibers– Molds and Yeasts

• Bacteria– The most diverse group– Heterotrophicp– Facultative– Anaerobic– Autotrophic

• Macrofouling Organismsg g– Zebra mussels, Asiatic clams– Shad and fish– Jellyfish


Bacteria• Environmental flexibility

– Aerobic – require oxygen– Anaerobic – require O2 absence– Facultative – either O2 or not

• Nutritional diversityy– Heterotrophs ‐ Organic carbon

• Most energetically favorable• Use organic C for energy & tissue• Use organic C for energy & tissue

– Autotrophs – Inorganic carbon• Energy from redox couple between

d d d idi d i ireduced and oxidized inorganics• Bicarbonate C used for cellular tissue• Some types, such as Sulfate Reducing Bacteria (SRB) can be very destructiveBacteria (SRB), can be very destructive


How Do We Monitor Microbes?• Planktonic – cfu / mL

– Traditional standard– Maintain < 104 cfu/mL

• Sessile – cfu / cm2Sessile cfu / cm– Emerging standard– Maintain < 105 cfu/cm2

• MonitoringC lt f / L– Culture cfu/mL

• Dip‐slides (Easicults, Paddles)• Petrifilm• Requires incubation time

– ATP (Adenosine TriPhosphate), rlu• Immediate• Includes all microbes

Micro bio assays performed in the– Micro‐bio assays performed in the laboratory (e.g. Legionella)

– On‐line sensors• BioGeorge• NeoSens (new)


How Do We Test For Microbes?

• Differential microbiologicalmicrobiological testing

• Tower wood– AnalysisAnalysis

– Zone of Inhibition

• Biological efficacy

• MicroscopyAerobic Bacteria Fungi SRB

Microscopy– Still

– Movie

– Live‐Dead Stain

• DNA testing

Pseudo & Enteric DN IRB Slym N ATP


How Do We Test For Microbes?• Differential

microbiological testing

• Tower wood– Analysis



• Microscopy

Metal screwdriver piercing wood

‐ Internal decay (biological attack)‐ Loss of structural integrity

‐ Surface delignification (chem. attack) ‐ Fuzzy ‐ cellulose fibers separatingdue to loss of lignin (delignification)

– Still

– Movie


• DNA testing







• Microscopy– Still

– Movie


• DNA testing

Chlorine CL-49







• Microscopy– Still

– Movie


• DNA testing


Biofouling ControlBiofouling Control

How Do We Control Microbes?

• Reduce microbes entering the system Pretreatment with chlorine or other biocideC l i i h• Control nutrients entering the system Organic carbon is the growth‐limiting nutrient Process leaks

• Control sunlight entering the water Cover decks, install louvers

• Apply antimicrobial chemicals to the cooling systemApply antimicrobial chemicals to the cooling system Oxidizing

• Chlorine, bromine, chlorine dioxide, peroxide, UV• Mostly non‐specific across organism typesMostly non specific across organism types

– Non‐oxidizing• Many types – Isothiazolin, DBNPA, Glutaraldehyde, Quaternary amines• Action is very specific to the organismAction is very specific to the organism

Oxidizing biocides are primary in large industrial systemsOxidizing biocides are primary in large industrial systems88


Oxidizing BiocidesChl i GChlorine Gas

Sodium Hypochlorite (“Bleach”)

h i h d l (“h hl id”)

Cl2 + H2O HOCl + HCll “ hl id” i i bi l

Both react with water to produce HOCl (“hypochlorous acid”)

– HOCl = “Hypochlorous acid” ‐ Antimicrobial– HCl = “Hydrochloric acid”, lowers pH

NaOCl + H2O HOCl + NaOH – Also produces HOCl– NaOH = “Caustic”, raises pH

HOCl OCl‐ + H+HOCl OCl H– HOCl is a weak acid in equilibrium with OCl‐– Both are considered “Free Available Chlorine” (FAC)– HOCl is faster acting as a biocideHOCl is faster acting as a biocide

• Electrical neutrality and smaller effective diameter allow it to penetrate rapidly through cell walls


Hypochlorous Acid and Hypobromous Acid ‐ Dissociation Curves

pK 7 5 pK = 8 5pKa = 7.5 pKa = 8.5

BothBoth HOClHOCl andand OClOCl‐‐ Are Considered “Free Available Chlorine” or FACAre Considered “Free Available Chlorine” or FAC

At pH 8.5, 50% of the Bromine is in the most effective form Vs. 5% for ChlorineAt pH 8.5, 50% of the Bromine is in the most effective form Vs. 5% for Chlorine

Both Both HOClHOCl and and OClOCl‐‐ Are Considered Free Available Chlorine or FACAre Considered Free Available Chlorine or FAC


Hypochlorous Acid Plus BromineImproving Chlorine Effectiveness by Converting to Bromine

HOCl + N B HOB + N Cl• HOCl + NaBr HOBr + NaCl• Bromine is a “weaker” acid (higher pKa)

Less dissociated at alkaline pH– Less dissociated at alkaline pH

– Effective at lower residuals

• Less tendency to “tie up” with ammonia y p– Chloramines are not very effective on algae

! Less corrosive to copper alloys than chlorine


Disinfection Performance of Bromine Vs. Chlorinein Presence of 2 ppm Ammonia at pH 8 2in Presence of 2 ppm Ammonia at pH 8.2

Disinfection Performance of Bromine Vs. Chlorinein Presence of 2 ppm Ammonia at pH 7 2in Presence of 2 ppm Ammonia at pH 7.2

Chlorine Dioxide for Microbiological Control

• Overcomes many of the issues associated with chlorine and bromine– More effective in highly contaminated systems

• Contact systems and Grey water)y y– Not affected by pH– More effective at penetrating biofilms – Generally shot‐fed– Does not tie up with ammonia to form weak chloramines– More effective on macrofouling (zebra mussels, Asiatic clams)– Much less corrosive to copper alloys

• DisadvantagesHi h d h hl i b i– Higher cost per pound than chlorine or bromine

– Traditionally generated on site using 2 or 3 chemicals• Sodium chlorite, hydrochloric acid, sodium hypochlorite

• Newer lower cost generation technology based on sodium chlorate• Newer, lower cost generation technology based on sodium chlorate– NaClO3 + ½ H2O2 + ½ H2SO4 ClO2 + ½ Na2SO4 + ½ O2 + H2O– Sodium chlorate and hydrogen peroxide are supplied as a stable blend– Lower chemical cost for large Power systems – Improved handling and safety – no hypochlorite or hydrochloric acidp g y yp y

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More on Chlorine Dioxide TomorrowMore on Chlorine Dioxide TomorrowProperty of ChemTreat, Inc. Do not copy without permission.

Cooling Microbiology SummaryCooling Microbiology Summary• Microbes thrive in cooling systems• Microbes prefer surfaces – Sessile• Microbes grow Fast!• Biofouling

– Impedes heat transfer– Increases pressure drop– Causes corrosion (MIC)– Entraps silt and clogs tower fill

C h h l h i ( i ll )– Can have health impacts (Legionella)• Several monitoring methods

– Culture, ATP, and on‐line sensorPl kt i d S il– Planktonic and Sessile

• Can be controlled with Antimicrobials (biocides)– Oxidizing – Chlorine, Bromine, Chlorine Dioxide

Non Oxidizing For specific needs– Non‐Oxidizing – For specific needs


Cooling Water FundamentalsThank You!

Ray PostDirector, Cooling Water Technologies, g gMobile: 804‐627‐2369 [email protected]


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General Types of Counter‐Flow Fill - ChemTreatdev.chemtreat.com/wp-content/uploads/2012/12/2c-Cooling-Water... · • Use organicorganic CC forfor energyenergy && tissuetissue –