1. Microbial Life in Paper Machine: Prevention and Control
TAPPI Monograph: Microorganisms in Papermaking
Piyush K. Verma, Nishi K. Bhardwaj, R. Varadhan
Avantha Centre for Industrial R & D, Yamuna Nagar (Haryana)
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2. Why do microbes grow? i.e. machines contain:
Varied oxygen levels
Nutrients
Suitable pH range
Surfaces
Sunlight
Temperature
Increased surface area
Increased filler levels
Water system closure
Recycled pulp
i.e. machines contain:
Ideal conditions for microbial growth
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3. Changes in Operational / Industry Practices
Water system closure
Noxious chemical cycle up
Nutrients cycle up
Stagnant chests
Neutral to alkaline conditions
Increased use of recycled pulps
Large chests constructed with long dwell times
Reduced biocide programs due to cost constraints
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4. Non Microbial Deposits
Filamentous bacteria
Algae
Fungi
Non Microbial Deposits
In addition to wood fibers, fibrils, fines and fillers, other materials also get deposited:
Strength additives
Uncooked starch granules
Mimic microbes
Moulds/ Yeast
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

5. Comparison of Biological Activity Test Methods
Time
Accuracy
Quantitative results
Comments
Bio-Lert
1-4 hours
Very Good
Yes
Rapid simple procedure
Standard Plates
hours
Excellent
Time consuming procedure
Dip-Stick
24 hours
Results not rapid enough
ATP- luminescence
<30 min
Good
May be
Simple test, results not rapid enough, pulp times can interfere with test
TTC, Indicator Dyes
4-48 hours
Results not rapid enough, sample preparation sometimes complicated
Ninhydrin Spray
5 min
Fair No
Rapid amino-nitrogen test, not quantitative
Reference: Bajpai P (2012) Slime Control. In: Bajpai P (eds) Biotechnology for pulp and paper processing.

6. pH Preference of Microbes? Effect of pH on microbial growth
Alkaline Vs. Acid
Effect of pH on microbial growth
Acid
Alkaline
Typical
fungi
filamentous bacteria
Predominant bacteria
single cell
Minor
protozoa
Organism
algae
Biocide needs 1X
2-4 X
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

7. Filamentous bacteria, algae, protozoa, worms
Machine Surfaces
Headbox
Approach piping
Frame
Fresh Water
Filamentous bacteria, algae, protozoa, worms
Broke Towers
Heavily contaminated
Back Water
Entry (Check) Points for Microbes
White Water System
Recycled Fibres
Paper Mill Additives

8. Why do We Care About Microbes?
Reduced paper quality & strength
Odor problems/ Obnoxious odors
Rejected paper, Customer complaints
Machine downtime
Viscosity deterioration of coating batches
Brightness , shade issues
Screening / filtering issues
Corrosion (MIC)
Decreased profitability
Deposit from foil pan
Sheet defects
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

9. Mill Safety Issues
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

10. Types of Microbes Involved in MIC
Biocorrosion
Microbiologically influenced corrosion
Direct
Biofilm formation
Indirect
Corrosive metabolic byproducts
Types of Microbes Involved in MIC
Metal depositors
Slime forming bacteria
Acid formers
Sulfate reducing bacteria (SRB)

11. Slime Forming Bacteria
Typically aerobic
All produce an exopolymer
Contains water, polysaccharides & protein
Traps inorganic salts, fibers, fines, fillers & debris
Metal Depositors
Gallionella, Sphaerotius, Crenothrix, Leptothrix
All aerobic; oxidize either iron or manganese to oxides

12. Sulfate Reducing Bacteria
Acid Producers
Clostridium (anaerobic)
Thiobacillus (aerobic)
Sulfate Reducing Bacteria
All SRBs are anaerobic
Desulfovibrio most common genus
SRBs do not attack metal directly
Typically produce localized pitting corrosion

13. Monitoring Biocorrosion
After it has occurred
Post mortem examination
In situ monitoring
Difficult
Side stream monitoring
Suspension of coupons in raw or process water
Biofouling sampling device

14. Strategies to control microorganisms
Water quality
Housekeeping
Oxidants- short term kill
Biocides- short and long term kill
Thermal
Radiation (UV/ gamma)
Key Elements of Microbial Control Program
Engineering survey
Microbiological survey
Product selection
Implementation/ Follow up

15. Microbiological Survey
Engineering Survey
Three major systems of concern
Recirculated water system
Stock system
Additives system
Tank volumes/ capacity
Sampling points
Recycled lines/ Dead legs
Freshwater sources
Temperature and pH
Process additives
Current biocide program
Microbiological Survey
Deposit analysis
Microbiological analysis
Chemical analysis
Microbial survey of process waters, additives & stock chests

16. Monitoring and Follow Up
Product Selection
Oxidizing biocides (very fast kill; short duration)
May be stabilized (hydantoins, sulfamate)
Typically continuous dosing
Non oxidizing biocide (slower kill; Longer half life)
Typical intermittent dosing
Inhibits reproduction, doesn’t necessary kill
Non biocidal technology
Enzymes, biodispersants & adjuvants
Monitoring and Follow Up
Employ routine monitoring , Machine runnability, quality, defects etc.

17. Oxidants and Biocides: Functions
Oxidants and Non Oxidizing Biocides:
Kill all aerobic bacteria
Maintain adequate level of oxidant and/or biocide
Oxidants:
Oxidize compounds
Oxidants: Oxidation of processing chemicals, e.g. polyacrylic acid and CMC, limits the levels that can be used.

18. Oxidants Hydrogen Peroxide Short term MB control
Environmentally friendly
Microbial resistance (degradation to water and oxygen by catalase enzyme)
Hypochlorite & Chlorine
Affects viscosity
Chlorinated organic compounds
Effective at neutral to acid pH
Very corrosive

19. Oxidants Ozone Excellent Short term MB Control Peracetic acid
Environmentally friendly
Sodium Chlorite
Neutral to acid pH
Chlorine dioxide
Does not chlorinate

20. Biocides (Non–oxidizing)
Mills that produce food contact paper and paperboard
Iso thiazolin
Benzisothiazolin
Glutaraldehyde
Bromonitropropane diol
Sodium orthophenyl phenate
Thione
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

21. Additional Non-oxidizing Biocides
Methylisothiazolin(MIT)
Tetrakishydroxymethyl phosphonium sulfate (THPS)
Dodecylquanidine(DGH)
Oxazolidines
Dibromodicyanobutane (DBDCB)
Methylenebiosthiocyanate( MBT)
Hydantoins
HCHO
Bromohydroxyacetophenone( BHAP)
Adamantanes
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

22. Microbial Tolerance or Resistance to Oxidants and Biocides
Biofilm
Tolerance
Resistance
Prevention of biofilm formation
Cleaning
Sterilization

23. Areas of Concern for Paper Mill Microbial Control
Unloading raw materials
Adequate microbiological control in slurry prior to unloading
Uncontaminated hoses, lines, pumps, etc.
Each raw material should have its own unloading system
Biocide-biocide compatibility, Biocide-process chemical compatibility
Raw material storage/ screening facilities
Adequate MB control in raw material storage tank
Storage tank recirculation system, good mixing
Equipment to add oxidants and/or biocides into the intake side of the recirculation pump
Biocide-biocide compatibility, biocide-process chemical compatibility
Water quality (closed water system: water reuse)

24. Coating
Adequate MB control for each coating ingredient
Coating biocide should be effective and compatible
Coating storage tank
Key area for intensive bacterial monitoring
Adequate MB control
Run tank (excess coating typically recycled back to run tank)
Crucial area for MB control
Recirculation line from coater to coater feed tank

25. Boilouts-Chemical Cleaning Programs
Goals of Boilout
Remove Organic and inorganic build-up
Remove deposits
Clean the forming fabric
Housekeeping = Runnability
Boilout Benefits
Prevention of Premature Slime Accumulation
Prevention of Corrosion Pitting
Prevention of Scale Formation
Removal of Organic Deposits

26. Biolout Components Typical Boilout Caustic (Sodium Hydroxide)
Acid (Sulfuric)
Organic Penetrants
Inorganic Dispersants
Forming Agents
Typical Boilout
Pre Boilout wash-up
pH of
Temperature of F
Re-circulation, Neutralization

27. New Technology Options
Modes of action of microbicides, biodispersants, enzymes and biofilm inhibitors
Product
Mode of Action
Microbiocides
Reduce/ control microbial populations
Biodispersants
Loosen wet-end deposits and support the effect of microbiocides
Enzymes
Cleave specific bonds in the EPS
Biofilm inhibitors
Prevent the formation of a concentrated EPS layer around cells thus preventing biofilm growth
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

28. New Technology Options
Enzymes & Biodispersants
% typical usage rates
Proprietary combinations of enzymes, dispersants and surfactants
Neutral pH Boilouts: Effective in removing MB, starch, cellulosic and protein containing deposits
 Alternative if high or low pH solutions are problematic
Use of dispersants and penetrants with standard temperature and time
Accelerates removal of general wet end deposits during neutral boilout procedures
Reduces boilout time, maintenance on machine can be completed during the boilout
Causes no problems in waste treatment facilities

29. Green Principles & Enzymes
Prevent Waste 
Design safer chemicals and products
Design less hazardous chemical synthesis
Use renewable feedstock
Use catalysts, not stoichiometric reagents
Avoid chemical derivatives
Maximize steam economy
Use safer solvents and reaction conditions
Increase energy efficiency
Design chemicals and products to degrade after use
Analyze in real time to prevent pollution
Minimize the potential for accidents
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

30. Monthly average values of Total bacterial Count at the wire pit in a tissue mill using the enzymatic biocide. Red bars indicate base line values
Bacterial counts at the wire pit in a tissue mill after the usage of enzymatic biocide
Reference: Juan C. Cotrino and Victor Ordonez (2011), TAPPI Papercon Conference

31. Monthly average values of Total bacterial Count at the machine chest in an OCC recycling mill. Red bar indicate base line values
Bacterial count at the machine chest of an OCC recycling mill after the usage of enzymatic biocide.
Reference: Juan C. Cotrino and Victor Ordonez (2011), TAPPI Papercon Conference

32. Summary
Microbial colonization of machines increases downtime and decreases profitability.
Biofilms form deposits that lead to sheet defects.
Microbial spoilage of additives and fibers can alter pH, cause odors, and reduce sheet strength and quality.
Understanding the papermaking process and basic microbial physiology is essential in diagnosing and solving problems.
Monitor microbiological contaminants throughout the paper mill.
Define biocide treatment with lab studies and confirm with field testing.
Follow biocide manufacturers recommendations.
Follow up with routine monitoring.

33. Summary
Effective house cleaning & biocide application are integral parts of successful integrated microbial control strategies.
Oxidants and biocides must be selected with both efficacy and compatibility in mind.
Oxidant and biocide application techniques must adhere to environment, safety, and health regulations.
Resistance development is a reality. Oxidant, biocide, and microbial testing application must be accurate, precise, and as “real time” as possible.
Oxidants and biocides must not only be effective, they must not interfere or compromise subsequent papermaking applications.

34. Summary Mechanical cleaning to remove deposits.
Caustic cleaning with water/ dispersant flush.
After repairs, system refilled with water plus dispersant and non-oxidizing biocide that are non-aggressive to metallurgy; repeated as needed.
Under “normal operations”, system treated with nonionic dispersant and biocide.
Successful boilouts depend on: Adequate time, Proper pH, (alkalinity), Correct temperature, Solution formulation, Proper wash-up after the boilout.
Work with machine crew to establish good practices: Safety, Set-up, Clean-up & Inspection.

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