microbial life in paper machine: prevention and control piyush k. verma, nishi k. bhardwaj, r....

Microbial Life in Paper Machine: Prevention and Control

Piyush K. Verma, Nishi K. Bhardwaj, R. VaradhanAvantha Centre for Industrial R & D, Yamuna Nagar (Haryana)

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TAPPI Monograph: Microorganisms in Papermaking

Why do microbes grow?

Suitable pH rangeVaried oxygen levelsNutrients

Surfaces

Temperature

i.e. machines contain:

Ideal conditions for microbial growth

Increased surface area

Recycled pulpWater system closureIncreased filler levels

Sunlight

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Best Maintenance Practices in Pulp and Paper Mill to Improve Profitability

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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

Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

Non Microbial Deposits

Microbial Deposits

In addition to wood

fibers, fibrils, fines and

fillers, other materials

also get deposited:

• Strength additives

• Uncooked starch

granules

Mimic microbes

AlgaeFilamentous bacteria Fungi

Moulds/ Yeast

Method Time Accuracy Quantitative results

Comments

Bio-Lert 1-4 hours Very Good Yes Rapid simple procedure

Standard Plates

48-72 hours

Excellent Yes Time consuming procedure

Dip-Stick 24 hours Yes Yes Results not rapid enough

ATP-luminescence

<30 min Good May be Simple test, results not rapid enough, pulp times

can interfere with testTTC, Indicator

Dyes4-48 hours Good Yes Results not rapid

enough, sample preparation sometimes

complicatedNinhydrin

Spray5 min Fair No Rapid amino-nitrogen

test, not quantitative

Comparison of Biological Activity Test Methods

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 bacteria

single cell single cell

Typical filamentous bacteria

Minor protozoa protozoaOrganism algae algae

Biocide needs

1X 2-4 X

Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

Entry (Check) Points for Microbes

White Water SystemRecycled Fibres

Broke TowersHeavily contaminated

Machine Surfaces• Headbox

• Approach piping• Frame

Back Water

Paper Mill Additives

Fresh WaterFilamentous bacteria,

algae, protozoa, worms

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

Why do We Care About Microbes?

Deposit from foil

pan

Sheet defects

Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

Mill Safety Issues

Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

BiocorrosionMicrobiologically 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

Key Elements of Microbial Control Program

Engineering survey

Microbiological survey

Product selection

Implementation/ Follow up

Strategies to control microorganisms Water quality

Housekeeping

Oxidants- short term kill

Biocides- short and long term kill

Thermal

Radiation (UV/ gamma)

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

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

HCHOReference 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 = RunnabilityBoilout 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

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

Modes of action of microbicides, biodispersants, enzymes and biofilm inhibitors

Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.

New Technology OptionsEnzymes & 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.

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 wire pit in a tissue mill using the enzymatic biocide. Red bars 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

Monthly average values of Total bacterial Count at the machine chest in an OCC recycling mill. Red bar indicate base line values

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 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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