Prevention & Control

Report
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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Best Maintenance Practices in Pulp and Paper Mill to Improve Profitability
Why do microbes grow?
Sunlight
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Best Maintenance Practices in Pulp and Paper Mill to Improve Profitability
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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Best Maintenance Practices in Pulp and Paper Mill to Improve Profitability
Microbial Deposits
Filamentous bacteria
Algae
Fungi
Non Microbial Deposits
In addition to wood
fibers, fibrils, fines and
fillers, other materials
also get deposited:
Moulds/ Yeast
•
Strength additives
•
Uncooked
granules
Mimic microbes
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
starch
Comparison of Biological Activity Test Methods
Method
Time
Accuracy Quantitative
results
Comments
Bio-Lert
1-4 hours Very Good
Yes
Rapid simple procedure
Standard
Plates
Dip-Stick
48-72
hours
24 hours
Excellent
Yes
Yes
Yes
Time consuming
procedure
Results not rapid enough
ATP<30 min
luminescence
Good
May be
TTC, Indicator 4-48 hours
Dyes
Good
Yes
Fair
No
Ninhydrin
Spray
5 min
Simple test, results not
rapid enough, pulp times
can interfere with test
Results not rapid
enough, sample
preparation sometimes
complicated
Rapid amino-nitrogen
test, not quantitative
Reference: Bajpai P (2012) Slime Control. In: Bajpai P (eds) Biotechnology for pulp and paper processing.
pH Preference of Microbes?
Alkaline Vs. Acid
Effect of pH on microbial growth
Acid
Alkaline
Typical
fungi
filamentous
bacteria
Predominant
single cell
single cell
Typical
filamentous
bacteria
protozoa
algae
protozoa
algae
1X
2-4 X
bacteria
Minor
Organism
Biocide
needs
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
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
Why do We Care About Microbes?
Deposit
from foil
pan
 Reduced paper quality & strength
 Odor problems/ Obnoxious odors
 Rejected paper, Customer complaints
Sheet
defects
 Machine downtime
 Viscosity deterioration of coating batches
 Brightness , shade issues
 Screening / filtering issues
 Corrosion (MIC)
 Decreased profitability
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
Mill Safety Issues
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
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)
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
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
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
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
Engineering Survey
 Three major systems of concern  Recycled lines/ Dead legs
 Recirculated water system
 Freshwater sources
 Stock system
 Temperature and pH
 Additives system
 Process additives
 Tank volumes/ capacity
 Current biocide program
 Sampling points
Microbiological Survey
 Deposit analysis
 Microbiological analysis
 Chemical analysis
 Microbial survey of process waters, additives & stock chests
Product Selection
• Oxidizing biocides (very fast kill; short duration)
o May be stabilized (hydantoins, sulfamate)
o Typically continuous dosing
• Non oxidizing biocide (slower kill; Longer half life)
o Typical intermittent dosing
o Inhibits reproduction, doesn’t necessary kill
• Non biocidal technology
o Enzymes, biodispersants & adjuvants
Monitoring and Follow Up
• Employ routine monitoring , Machine runnability, quality, defects
etc.
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.
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
Oxidants
Ozone
 Excellent
 Short term MB Control
Peracetic acid
 Short term MB control
 Environmentally friendly
Sodium Chlorite
 Short term MB control
 Neutral to acid pH
Chlorine dioxide
 Does not chlorinate
 Short term MB control
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.
Additional Non-oxidizing Biocides
 Methylisothiazolin(MIT)
 Tetrakishydroxymethyl phosphonium sulfate (THPS)
 Dodecylquanidine(DGH)
 Oxazolidines
 Dibromodicyanobutane (DBDCB)
 Methylenebiosthiocyanate( MBT)
 Hydantoins
 HCHO
 Bromohydroxyacetophenone( BHAP)
 Adamantanes
 HCHO
Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
Microbial Tolerance or Resistance to Oxidants
and Biocides
 Biofilm
 Tolerance
 Resistance
 Prevention of biofilm formation
 Cleaning
 Sterilization
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)
 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)
Adequate MB control
Crucial area for MB control
 Recirculation line from coater to coater feed tank
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
Biolout Components
 Caustic (Sodium Hydroxide)
 Acid (Sulfuric)
 Organic Penetrants
 Inorganic Dispersants
 Forming Agents
Typical Boilout
 Pre Boilout wash-up
 pH of 12-12.5
 Temperature of 1300-14500F
 Re-circulation, Neutralization
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.
New Technology Options
Enzymes & Biodispersants
 0.1-0.5% 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
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.
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
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
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.
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.
Summary
 Mechanical cleaning to remove deposits.
 Caustic cleaning with water/ dispersant flush.
 After repairs, system refilled with water plus dispersant and nonoxidizing 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, Setup, Clean-up & Inspection.
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Best Maintenance Practices in Pulp and Paper Mill to Improve Profitability
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