Presentation on theme: "Microbial Life in Paper Machine: Prevention and Control Piyush K. Verma, Nishi K. Bhardwaj, R. Varadhan Avantha Centre for Industrial R & D, Yamuna Nagar."— Presentation transcript:
Microbial Life in Paper Machine: Prevention and Control Piyush K. Verma, Nishi K. Bhardwaj, R. Varadhan Avantha Centre for Industrial R & D, Yamuna Nagar (Haryana) IPPTA ZONAL SEMINAR ON Best Maintenance Practices in Pulp and Paper Mill to Improve Profitability TAPPI Monograph: Microorganisms in Papermaking
Why do microbes grow? Sunlight IPPTA ZONAL SEMINAR ON Best Maintenance Practices in Pulp and Paper Mill to Improve Profitability
IPPTA ZONAL SEMINAR ON 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 bacteriaFungi Moulds/ Yeast
MethodTimeAccuracy Quantitative results Comments Bio-Lert1-4 hoursVery GoodYesRapid simple procedure Standard Plates 48-72 hours ExcellentYes Time consuming procedure Dip-Stick24 hoursYes Results not rapid enough ATP- luminescence <30 minGoodMay be Simple test, results not rapid enough, pulp times can interfere with test TTC, Indicator Dyes 4-48 hoursGoodYes Results not rapid enough, sample preparation sometimes complicated Ninhydrin Spray 5 minFairNoRapid 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 AcidAlkaline Typicalfungi filamentous bacteria Predominant bacteria single cell Typical filamentous bacteria Minorprotozoa Organismalgae Biocide needs 1X2-4 X Reference TAPPI Monograph: Microorganisms in Papermaking, Papercon, 2011.
Entry (Check) Points for Microbes White Water System Recycled Fibres Broke Towers Heavily contaminated Machine Surfaces Headbox Approach piping Frame Back Water Paper Mill Additives Fresh Water Filamentous bacteria, algae, protozoa, worms Fresh Water Filamentous 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.
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
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)
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.
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 1300-1450 0 F Re-circulation, Neutralization
New Technology Options Product Mode of Action MicrobiocidesReduce/ control microbial populations BiodispersantsLoosen wet-end deposits and support the effect of microbiocides EnzymesCleave 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 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.
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.
IPPTA ZONAL SEMINAR ON Best Maintenance Practices in Pulp and Paper Mill to Improve Profitability