12.1 Disinfection Flashcards
what three pathogens should disinfection remove?
bacteria, viruses, amebic cysts
is disinfection equivalent to sterilization (destruction of all living organisms?
no
used in water treatment to reduce pathogens to an acceptable level
disinfection
what is the most common disinfecting chemical used?
chlorine
what is formed when chlorine is added to water?
a mixture of hypochlorus acid (HOCl) and hydrochloric acid (HCl)
what is the reaction of chlorine and water dependent on?
pH
what are the two differences between use of hypochlorite ions and free chlorine?
resultant pH and relative amounts of HOCl/OCl at equilibirum
free chlorine is relatively stable in pure water and reacts slowly with ___________ and rapidly with _________
NOM, sunlight
photolytic reaction with chlorine and sunlight is with the hypochlorite and the reaction products are ____________, ___________ ion, and __________ ion
oxygen, chlorite, chloride
free chlorine tends to decrease ______ and each mg/L of chlorine added reduces __________ by up to 1.4 mg/L as CaCO3
pH, alkalinity
hypochlorites always contain excessive _________ and tend to raise ______
alkali, pH
what is formed when chlorine is added to water that contains natural or added ammonia
chloramines
what is formed when chlorine reacts with organic nitrogenous materials (proteins and amnio acids)?
organic chloramine complexes
chlorine that exists in water in chemical combination with ammonia or organic nitrogen compounds
combined chlorine
what is total chlorine comprised of?
free chlorine and combined chlorine
what chloramine dominates at high pH levels?
monochloramine
stabile free radical that reacts violently with reducing agents at high concentrations
chlorine dioxide
how is chlorine dioxide formed?
combining chlorine and sodium chlorite
unstable, pungent gas that is generated at the point of use due to its instability
ozone
four types of ozone generation?
photochemcial, electrolytic, radiochemical, discharge electrode
chemical disinfectants are ________ and can be compared based on their _________ power
oxidants, oxidizing
formed as a result of the reaction between chlorine and natural organic matter
disinfection byproducts
what disinfection mechanism does not produce byproducts?
UV radiation
