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Desinfection Technigues Desinfection Technigues Presentation Transcript

  • Disinfection and sterilisation
    • Disinfection
    • Sterilization
    • Disinfection : Benefit and By - product Risk
    • C x T a measure for disinfactant effectiveness
    • Biocidal efficiency, stability and effects of pH
    • Epidemiology
    • Applications
    Rob Slooten,
  • What‘s a germ ? Bean germ Skin germ       Disease germ     Hospital germ They are more or less aggressive !
  • Attributes of the Three Waterborne Pathogens of Concern in Water Treatment
  • Disinfection
    • Disinfection = reduction of germs, i.e. micro-organisms
    • physical methods :
      • heat: boiling, steam (120°C), pasteurisation (partial disinfection)
      • radiation: UV, Gamma-radiation
      • filtration: micro-, nanofiltration, reverse osmosis
    • chemical methods: in water treatment
    • chemicals are added to inactivate (or kill) pathogens found in the source water (i.e., lake, river, reservoir, or ground water from which water is drawn and treated).
    • Common effective disinfectants: chlorine, ozone, chlorine dioxide peracetic acid, hydrogene peroxide
    • Other less effective disinfectants: silversalts
  • Sterilisation
    • Sterilisation = killing of all micro-organisms including endospores
    • dry heat - hot air sterilization the water content of the biological material determines the effectiveness of heat
    • dry heat means always very high temperatures
    • save sterilization > 180°C
    10 min. 15-30 min. 60 min. 120 min. Bacillus anthrax spores - 5 min. 10 min. 20 min. Salmonella typhimurium 1 min. 12 min. 30 min. - Clostridium tetani spores - 8 min. 10-15 min. 30 min. E.Coli - 8 min. 15 min. 30 min. Staphylococcus aureus 180°C 160°C 140°C 120°C Organism
  • Disinfection and Sterilisation
    • Sterilisation = abolition of microbiological contamination
      • mainly medical applications
    • Disinfection = reduction of microbiological contamination
      • food & beverage
      • drinking water
      • process water
      • waste water
  • Disinfection : Benefit and By - product Risk By-product risk (Morris) Risk Dosage of Disinfectant Microbiological Risk Optimum Area
  • Demands for Disinfection
    • Sufficient germicidal potential
    • Reliable control of undesired microorganisms
    • Sufficient stability of the used agent under different process conditions
    • No formation of toxic, sensoric or ecologic harmful reaction products
  • Demands for Disinfection
    • No impeding of odour, taste or appearance of water and goods
    • Ability to measure the concentration of the disinfectant for continous control
    • Economy of application
  • Parameter of the disinfection process
    • Concentration
    • Contact time
    • Depot effect
    • Temperature Range of Application
    • Nutrient situation
    • Construction details of equipments
  • Relevance of water parameters
  • Loss of disinfection power
  • C x T a measure for disinfactant effectiveness disinfection is monitored using a concept referred to as the "CxT" value. This value relates the amount of time ("T") needed for a concentration of residual disinfectant ("C") to inactivate a particular micro-organism under specific operating conditions. Water treatment plants are given "credit" for achieving different levels of microorganism inactivation. http://www.clo2.com/wtupgrade/disinfection.html
  • C x T a measure for disinfactant effectiveness Therefore, the best disinfectants can achieve highest disinfection by the lowest "CxT" product . Water plants usually have "CxT" requirements that insure adequate disinfection under various operating conditions and extremes, such as high flows and low temperatures, for example. The "CxT" Values will vary as a function of different disinfectants, temperatures and pH's. The "CxT" values for ClO2 are generally between those for free chlorine and ozone (see Table 3). http://www.clo2.com/wtupgrade/disinfection.html
  • Temperature influence on CxT values
  • Characteristics of Disinfectants disinfectant reaction velocity 3 4 5 6 7 8 9 spores vegetativ forms mykobakteria gramnegative yeast mould virus influence by ambience peracetic acid (PAA) F strong chlorine (Na-hypochlorite) F strong chlorine dioxide F strong jodine F strong formaldehyde I strong formaldehyde separ. comp. II strong glutaraldehyde F strong phenole and derivates F low alkohole F low quaternary comp. (Quats) I strong guanidine F moderate amphotere compounds I moderate efficiency strong > low strong efficiency only weak efficiency moderate efficiency F fast unefficient selektiv efficient I / II slow / very slow optimal pH-range range of action fungi bacteria grampositive 2
  • Influence of different pH-values
  • Overview Electromagnetic Spectrum 100 200 280 315 400 780 Vacuum UV UVC UVB UVA Infrared- rays X- and Gamma rays Visible light Wave length in nm Dependence of germ-sterilizing efficiency from wave length
  • Disinfection Capacity and Wave Length Wave length in nm 220 240 260 280 300 320 10 8 6 4 2 0 rel. units germ-sterilizing efficiency absorption of DNA 254 nm Hg resonance line
  • UV-Spectrum Low Pressure Lamp High Flux
    • capacity: ca. 200 W per meter arc length
    • Hg-vapour pressure: 0.01-0.001 bar
    • operation temperature 20 -150°C
    • yield disinfection relevant radiation at 254 nm: 35%
    • no emission below 240nm
    • lifetime: ca. 8 000 – 10 000 h
    Wave length in nm Intensity in rel. units 200 300 400 500 600 10 8 6 4 2 0
  • UV-Spectrum Medium Pressure Lamp Powerline
    • capacity: 2.000–10.000 W per meter arc length
    • Hg-vapour pressure 1 bar
    • operation temperature: 650 -850°C
    • yield of disinfection relevant radiation at 254nm: 17 %
    • especially suitable for photo chemistry
    • lifetime: ca. 8.000 h
    Wave length in nm Intensity in rel. Units 200 300 400 500 600 10 8 6 4 2 0
  • Comparison of Disinfect ants
  • Comparison of Disinfect ants
    • Two ways to go:
    • higher concentration - shorter reaction time
    • lower concentration - longer reaction time
  • What are Disinfection Byproducts? Disinfection byproducts are formed when disinfectants used in a water treatment react with bromide and/or natural organic matter (i.e., decaying vegetation) present in the source water. Different disinfectants produce different types or amounts of disinfection byproducts. Disinfection byproducts for which regulations have been established have been identified in drinking water, including trihalomethanes, haloacetic acids, bromate, and chlorite.
  • What Regulations Control Disinfection Byproducts? In December 1998, EPA published the Stage 1 Disinfectants/Disinfection Byproducts Rule that requires water systems to use treatment methods to reduce the formation of disinfection byproducts and to meet the following standards: total trihalomethanes (TTHM)(measured as the sum concentration of chloroform, bromoform, bromodichloromethane, and dibromochloromethane) at 80 parts per billion (ppb) , haloacetic acids (HAA5) (measured as the sum concentration of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid) at 60 ppb , bromate at 10 ppb , and chlorite at 1.0 parts per million (ppm). The standards for TTHM, HAA5, and bromate are annual averages. For chlorite, the standard is an average of a three samples taken at least monthly. Data from the ICR and research will be used to consider further disinfection byproduct control under a Stage 2 Disinfectants/Disinfection rule, scheduled to be published in May 2002.
  • Epidemiology
  • Treatment of Drinking Water
    • oxidation of undesired water compounds such as metals, sulphides, organics
      • ozone
      • chlorine dioxide
    • disinfection
      • ozone
      • chlorine dioxide
      • chlorine
      • UV
  • Application Drinking Water Water Supplier Lake Constance (Germany) „ Sipplinger Berg“ lake water sieve 15 µm ozone 0,8 ppm, 2-5 h two layer filter pumice - sand chlorine 0,4 ppm end user Municipal Utility Duisburg (Germany) „ Wittlaer“ bank filtrate ozone 1 ppm, 15 min activated carbon chlorine, chlorine dioxide 0,05 ppm end user multilayer filter
  • Application Drinking Water arsenic-elimination water work Bad Dürkheim (Germany)
    • reduction of arsenic from 0,02 ppm to 0,004 ppm (threshold value Germany: 0,01 ppm)
    wellwater 0,02 ppm As dosing FeCl 3 ozone 1,9 ppm, 25 min filtration over gravel UV-treatment end user
  • Waterwork Installation in Italy
    • Two units CDVa 600
    • Dilluted Chemicals
    • Flow proportional dosage
    • Performance: 600 g/h
  • Waterwork Installation in Poland
    • Two units CDKa 300
    • Concentrated chemicals
    • On-line measurement with Chlorine dioxide sensor
  • On-line Measurement
    • Chlorine dioxide specific sensor
    • Amperometric measurement principle
    • High accuracy
    • Membrane covered electrode
    • No cross sensitivity to Chorite (ClO 2 - ), Hypochlorite (OCl - ), Chlorige (HOCl), Chloride (Cl - )
  • Dulcoclean ® Compact Water Works
    • generation of drinking water by using:
      • chemically and microbiologically contaminated water
      • brackish water
    • performance:
      • 0,25 – 2 m³/h pure water
  • Installation Example System monitoring UV disinfection system UV disinfection system spring System monitoring stop valve rinse valve sample valves
  • New! Dulcodes Z Series
    • every type biodosimetrically tested at DVGW test laboratory for UV disinfection plants in Meindorf
    • aim: plants to be certified by DVGW (German registered association for gas and water)
  • Biodosimetric Validation
    • the radiation dose of the UV-system is determinated at different flow rates and UV transmissions by bacillus subtilis spores with well known UV-sensitivity
    • from the reduction of the test spores the specific UV-dose for the test point is calculated
    sensitivity of bacillus subtilis spores against UV-radiation