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
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
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
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.
oxidation of undesired water compounds such as metals, sulphides, organics
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