Presentation on theme: "Microbial Life in Paper Machine: Prevention and Control"— Presentation transcript:
1 Microbial Life in Paper Machine: Prevention and Control TAPPI Monograph: Microorganisms in PapermakingPiyush K. Verma, Nishi K. Bhardwaj, R. VaradhanAvantha Centre for Industrial R & D, Yamuna Nagar (Haryana)IPPTA ZONAL SEMINARONBest Maintenance Practices in Pulp and Paper Mill to Improve Profitability
2 Why do microbes grow? i.e. machines contain: Varied oxygen levelsNutrientsSuitable pH rangeSurfacesSunlightTemperatureIncreased surface areaIncreased filler levelsWater system closureRecycled pulpi.e. machines contain:Ideal conditions for microbial growthIPPTA ZONAL SEMINARONBest Maintenance Practices in Pulp and Paper Mill to Improve Profitability
3 Changes in Operational / Industry Practices Water system closureNoxious chemical cycle upNutrients cycle upStagnant chestsNeutral to alkaline conditionsIncreased use of recycled pulpsLarge chests constructed with long dwell timesReduced biocide programs due to cost constraintsIPPTA ZONAL SEMINARONBest Maintenance Practices in Pulp and Paper Mill to Improve Profitability
4 Non Microbial Deposits Filamentous bacteriaAlgaeFungiNon Microbial DepositsIn addition to wood fibers, fibrils, fines and fillers, other materials also get deposited:Strength additivesUncooked starch granulesMimic microbesMoulds/ YeastReference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
5 Comparison of Biological Activity Test Methods TimeAccuracyQuantitative resultsCommentsBio-Lert1-4 hoursVery GoodYesRapid simple procedureStandard PlateshoursExcellentTime consuming procedureDip-Stick24 hoursResults not rapid enoughATP- luminescence<30 minGoodMay beSimple test, results not rapid enough, pulp times can interfere with testTTC, Indicator Dyes4-48 hoursResults not rapid enough, sample preparation sometimes complicatedNinhydrin Spray5 minFairNoRapid amino-nitrogen test, not quantitativeReference: 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. AcidEffect of pH on microbial growthAcidAlkalineTypicalfungifilamentous bacteriaPredominant bacteriasingle cellMinorprotozoaOrganismalgaeBiocide needs1X2-4 XReference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
10 Types of Microbes Involved in MIC BiocorrosionMicrobiologically influenced corrosionDirectBiofilm formationIndirectCorrosive metabolic byproductsTypes of Microbes Involved in MICMetal depositorsSlime forming bacteriaAcid formersSulfate reducing bacteria (SRB)
11 Slime Forming Bacteria Typically aerobicAll produce an exopolymerContains water, polysaccharides & proteinTraps inorganic salts, fibers, fines, fillers & debrisMetal DepositorsGallionella, Sphaerotius, Crenothrix, LeptothrixAll aerobic; oxidize either iron or manganese to oxides
12 Sulfate Reducing Bacteria Acid ProducersClostridium (anaerobic)Thiobacillus (aerobic)Sulfate Reducing BacteriaAll SRBs are anaerobicDesulfovibrio most common genusSRBs do not attack metal directlyTypically produce localized pitting corrosion
13 Monitoring Biocorrosion After it has occurredPost mortem examinationIn situ monitoringDifficultSide stream monitoringSuspension of coupons in raw or process waterBiofouling sampling device
14 Strategies to control microorganisms Water qualityHousekeepingOxidants- short term killBiocides- short and long term killThermalRadiation (UV/ gamma)Key Elements of Microbial Control ProgramEngineering surveyMicrobiological surveyProduct selectionImplementation/ Follow up
15 Microbiological Survey Engineering SurveyThree major systems of concernRecirculated water systemStock systemAdditives systemTank volumes/ capacitySampling pointsRecycled lines/ Dead legsFreshwater sourcesTemperature and pHProcess additivesCurrent biocide programMicrobiological SurveyDeposit analysisMicrobiological analysisChemical analysisMicrobial survey of process waters, additives & stock chests
16 Monitoring and Follow Up Product SelectionOxidizing biocides (very fast kill; short duration)May be stabilized (hydantoins, sulfamate)Typically continuous dosingNon oxidizing biocide (slower kill; Longer half life)Typical intermittent dosingInhibits reproduction, doesn’t necessary killNon biocidal technologyEnzymes, biodispersants & adjuvantsMonitoring and Follow UpEmploy routine monitoring , Machine runnability, quality, defects etc.
17 Oxidants and Biocides: Functions Oxidants and Non Oxidizing Biocides:Kill all aerobic bacteriaMaintain adequate level of oxidant and/or biocideOxidants:Oxidize compoundsOxidants: 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 friendlyMicrobial resistance (degradation to water and oxygen by catalase enzyme)Hypochlorite & ChlorineAffects viscosityChlorinated organic compoundsEffective at neutral to acid pHVery corrosive
19 Oxidants Ozone Excellent Short term MB Control Peracetic acid Environmentally friendlySodium ChloriteNeutral to acid pHChlorine dioxideDoes not chlorinate
20 Biocides (Non–oxidizing) Mills that produce food contact paper and paperboardIso thiazolinBenzisothiazolinGlutaraldehydeBromonitropropane diolSodium orthophenyl phenateThioneReference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
22 Microbial Tolerance or Resistance to Oxidants and Biocides BiofilmToleranceResistancePrevention of biofilm formationCleaningSterilization
23 Areas of Concern for Paper Mill Microbial Control Unloading raw materialsAdequate microbiological control in slurry prior to unloadingUncontaminated hoses, lines, pumps, etc.Each raw material should have its own unloading systemBiocide-biocide compatibility, Biocide-process chemical compatibilityRaw material storage/ screening facilitiesAdequate MB control in raw material storage tankStorage tank recirculation system, good mixingEquipment to add oxidants and/or biocides into the intake side of the recirculation pumpBiocide-biocide compatibility, biocide-process chemical compatibilityWater quality (closed water system: water reuse)
24 CoatingAdequate MB control for each coating ingredientCoating biocide should be effective and compatibleCoating storage tankKey area for intensive bacterial monitoringAdequate MB controlRun tank (excess coating typically recycled back to run tank)Crucial area for MB controlRecirculation line from coater to coater feed tank
25 Boilouts-Chemical Cleaning Programs Goals of BoiloutRemove Organic and inorganic build-upRemove depositsClean the forming fabricHousekeeping = RunnabilityBoilout BenefitsPrevention of Premature Slime AccumulationPrevention of Corrosion PittingPrevention of Scale FormationRemoval of Organic Deposits
27 New Technology Options Modes of action of microbicides, biodispersants, enzymes and biofilm inhibitorsProductMode of ActionMicrobiocidesReduce/ control microbial populationsBiodispersantsLoosen wet-end deposits and support the effect of microbiocidesEnzymesCleave specific bonds in the EPSBiofilm inhibitorsPrevent the formation of a concentrated EPS layer around cells thus preventing biofilm growthReference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
28 New Technology Options Enzymes & Biodispersants% typical usage ratesProprietary combinations of enzymes, dispersants and surfactantsNeutral pH Boilouts: Effective in removing MB, starch, cellulosic and protein containing deposits Alternative if high or low pH solutions are problematicUse of dispersants and penetrants with standard temperature and timeAccelerates removal of general wet end deposits during neutral boilout proceduresReduces boilout time, maintenance on machine can be completed during the boiloutCauses no problems in waste treatment facilities
29 Green Principles & Enzymes Prevent WasteDesign safer chemicals and productsDesign less hazardous chemical synthesisUse renewable feedstockUse catalysts, not stoichiometric reagentsAvoid chemical derivativesMaximize steam economyUse safer solvents and reaction conditionsIncrease energy efficiencyDesign chemicals and products to degrade after useAnalyze in real time to prevent pollutionMinimize the potential for accidentsReference 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 valuesBacterial counts at the wire pit in a tissue mill after the usage of enzymatic biocideReference: 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 valuesBacterial 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 SummaryMicrobial 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 SummaryEffective 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.
35 IPPTA ZONAL SEMINARONBest Maintenance Practices in Pulp and Paper Mill to Improve Profitability