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1 General Types of Counter Flow Fill Decreasing tendency to clog Increasing performance 73

2 Fill for Severe Fouling Applications eg e.g. Contact Systems Integral Drip Points Low film specific surfaceareaarea High droplet surface due to integraldrip points Moderate performance Excellent anti fouling characteristics Thermal Performance Good Poor Hybrid Trickle (H/T) Fouling resistance in dirty water systems 74

3 SPX Marley Guidelines for Tower Fill Selection The combination of Biofouling, Silt, and Oil is severely fouling 75

4 Guidelines for Tower Fill Selection 19mm CF 21mm OF 19mm VF 25mm H/T Allowed TSS w/good <100 <200 <500 <1000 microbial control (ppm): Allowed TSS w/poor <25 <50 <200 <500 microbial control (ppm): Allowed Oil & Grease None <1 <5 <50 concentration (ppm) Allowed Fibers in water None None None None CF Cross Flute OF Offset Flute VF Vertical Flute HT Hybrid Trickle (Brentwood Ind. Product Designations) 76

5 Biofilm Development 1. Organics condition the surface 2. Pioneer organisms begin colonization 3. Colonies grow and diversify in bacterial types 4. Developing into a fully formed consortia (Log growth phase) 5. Microorganisms detach release into the bulk water Bulk water Planktonic organisms are a Subset of the Sessile organisms on the surface 77

6 MIC Microbiologically Induced Corrosion Planktonic Free swimming in bulk water Mostly aerobic Sessile Attached to a surface Mostly anaerobic Sulfate Reducing Bacteria (SRB) Convert Sulfate to corrosive Sulfide Acid producing bacteria Strongly implicated din Microbiologically Induced Corrosion (MIC) Sessile Planktonic Need to Monitor and Control Sessile Microorganisms 78

7 Cooling Water Flow Heat Transfer and Fluid Frictional Resistance Fluid Frictional Resistance Stagnant Boundary Layer (Mostly water) 20 80x Less Conductive than turbulent flow Visco elastic Layer Disproportionate Pressure Drop ¾ Brass tube, 10% Dia. reduction 70% DP increase U reduced 55% from 175 to 79 Btu/hr ft 2 F 79

8 Higher life forms Protozoa Amoeba Ciliates Biofouling Organisms Algae Require sunlight for growth (tower deck) Convert bicarbonate into organic carbon food for bacteria Food dfor protozoa and higher h life forms Fungi Break down complex organics tower wood fibers Molds and Yeasts Bacteria The most diverse group Heterotrophic Facultative Anaerobic Autotrophic Macrofouling Organisms Zebra mussels, Asiatic clams Shad and fish Jellyfish 80

9 Bacteria Environmental flexibility Aerobic require oxygen Anaerobic require O 2 absence Facultative either O 2 or not Nutritional diversity Heterotrophs Organic carbon Most energetically favorable Use organic C for energy & tissue Autotrophs Inorganic carbon Energy from redox couple between reduced dand oxidized d inorganicsi Bicarbonate C used for cellular tissue Some types, such as Sulfate Reducing Bacteria (SRB), can be very destructive 81

10 How Do We Monitor Microbes? Planktonic cfu / ml Traditional standard Maintain < 104 cfu/ml Sessile cfu / cm2 Emerging standard Maintain < 105 cfu/cm2 Monitoring Culture C lt cfu/ml f / L Dip slides (Easicults, Paddles) Petrifilm Requires incubation time ATP (Adenosine TriPhosphate), rlu Immediate Includes all microbes Micro Micro bio bio assays performed in the laboratory (e.g. Legionella) On line sensors BioGeorge NeoSens (new) 82

11 How Do We Test For Microbes? Differential microbiological testing Tower wood Analysis Zone of Inhibition Biological efficacy Microscopy Still Movie Live Dead Stain DNA testing Aerobic Bacteria Fungi SRB Pseudo & Enteric DN IRB Slym N ATP 83

12 How Do We Test For Microbes? Differential microbiological testing Tower wood Analysis Zone of Inhibition Biological efficacy Microscopy Metal screwdriver piercing wood Internal decay (biological attack) Loss of structural integrity Surface delignification (chem. attack) Fuzzy cellulose fibers separating due to loss of lignin (delignification) Still Movie Live Dead Stain DNA testing 84

13 How Do We Test For Microbes? Differential microbiological testing Tower wood Analysis Zone of Inhibition Biological efficacy Microscopy Still Movie Live Dead Stain DNA testing Chlorine CL-49 85

14 How Do We Test For Microbes? Differential microbiological testing Tower wood Analysis Zone of Inhibition Biological efficacy Microscopy Still Movie Live Dead Stain DNA testing 86

15 Biofouling Control

16 How Do We Control Microbes? Reduce microbes entering the system Pretreatment with chlorine or other biocide 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 system Oxidizing Chlorine, bromine, chlorine dioxide, peroxide, UV Mostly non specific across organism types Non oxidizing Many types Isothiazolin, DBNPA, Glutaraldehyde, Quaternary amines Action is very specific to the organism Oxidizing biocides are primary in large industrial systems 88

17 Oxidizing Biocides Chlorine Gas Sodium Hypochlorite ( Bleach ) Both react with ihwater to produce HOCl ( hypochloroushl acid ) Cl 2 + H 2 O HOCl + HCl HOCl = Hypochlorous acid Antimicrobial i HCl = Hydrochloric acid, lowers ph NaOCl + H 2 O HOCl + NaOH Also produces HOCl NaOH = Caustic, raises ph 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 biocide Electrical neutrality and smaller effective diameter allow it to penetrate rapidly through cell walls 89

18 Hypochlorous Acid and Hypobromous Acid Dissociation Curves pk a = pk a = Both HOCl and OCl Are Considered Free Available Chlorine or FAC At ph 8.5, 50% of the Bromine is in the most effective form Vs. 5% for Chlorine 90

19 Hypochlorous Acid Plus Bromine Improving Chlorine Effectiveness by Converting to Bromine HOCl + NB NaBr HOBr + NCl NaCl Bromine is a weaker acid (higher pka) Less dissociated at alkaline ph Effective at lower residuals Less tendency to tie up with ammonia Chloramines are not very effective on algae! Less corrosive to copper alloys than chlorine 91

20 Disinfection Performance of Bromine Vs. Chlorine in Presence of 2 ppm Ammonia at ph 82 in Presence of 2 ppm Ammonia at ph 8.2

21 Disinfection Performance of Bromine Vs. Chlorine in Presence of 2 ppm Ammonia at ph 72 in Presence of 2 ppm Ammonia at ph 7.2

22 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) 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 Disadvantages 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 NaClO 3 + ½ H 2 O 2 + ½ H 2 SO 4 ClO 2 + ½ Na 2 SO 4 + ½ O 2 + H 2 O 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 acid More on Chlorine Dioxide Tomorrow 94

23 Cooling 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 Can have health hi impacts (Legionella) Several monitoring methods Culture, ATP, and on line sensor Planktonic and Sessile Can be controlled with Antimicrobials (biocides) Oxidizing Chlorine, Bromine, Chlorine Dioxide Non Oxidizing For specific needs 95

24 Cooling Water Fundamentals Thank You! Ray Post Director, Cooling Water Technologies Mobile: