Disinfection Flashcards
Distribution 1
living organisms, microscopic and usually consist of a single cell, use organic matter for their food and produce waste products as a result of their life processes
bacteria
a means of measuring chlorine concentration by color development resulting from a chemical reaction between chlorine and the reagent DPD ( darker color, high concentration)
DPD chlorine analysis
addition of chlorine to water until the chlorine demand has been satisfied
breakpoint chlorination
compounds formed by the reaction of hypochlorous acid (or aqueous chlorine) with ammonia
chloramines
difference between the amount of chlorine added to water and the amount of residual chlorine remaining after a given contact time
chlorine demand
concentration of chlorine present in water after the chlorine demand has been satisfied
chlorine residual
organic compounds combined with chlorine
chlororganic
group of bacteria found in the intestines of warm blooded animals and also in plants, soil, air and water
coliform
sum of the chlorine species composed of free chlorine and ammonia, including monochloramine, dichloramine, and trichloarmine
combined chlorine
process designed to kill of inactivate most microorganisms in water, including essentially all pathogenic bacteria
disinfection
portion of the total available residual chloronine composed of dissolved chlorine gas (cl2), hypochlorous acid (HOCl), and hypochlorite ion (OCl-) remaining in water after chlorination
free available residual chlorine
High Test Hypochlorite (HTH)
calcium hypochlorite or Ca(OCl)2
describes organisms that use organic matter for energy and growth
heterotrophic
chemical compounds containing available chlorine used for disinfection ( available in liquids or solids, in barrels, drums, or cans
hypochlorite
weak acid that is formed when chlorine is mixed with water ( strongest disinfectant of the different forms of chlorine
hypochlorous acid (HOCl)
Most Probable Number of coliform group organisms per unit volume of sample water
MPN
an aerobic process in which bacteria reduce the ammonia and organic nitrogen in water into nitrite and then nitrate
nitrification
organisms including bacteria and viruses or cysts that are capable of causing diseases in a host
pathogenic organisms
What are the most commonly used hypochlorite compounds?
Sodium hypochlorite followed by calcium hypochlorite
What are the 3 methods used for disinfecting water mains?
1) Tablet method
2) Continuous Feed method
3) Slug method
Best suited for short sections of pipe and on small diameter pipes
- sufficient tablets are added to give a dose of 25-50mg/L
- pipe is slowly filled with water and left for 24 hrs
- residual should be greater than 25mg/L through out the pipe
tablet method
preliminary flushing
- solution of at least 25mg/L free chlorine injected into pipe as its being filled
- added at a ratio to ensure a 10 mg/L residual will remain and the end of 24 hrs
continuous feed method
used for long, large diameter mains
- calcium hypochlorite tablets are placed in the main during construction and filled with water
- dose to produce a concentration of 100 mg/L with contact time of 3 hours
- ensure >50mg/L residual
slug method
What are the 3 methods to disinfecting storage tanks?
1) Complete fill
2) Surface Spray
3) Partial fill
tank filled to overflow and enough chlorine for 10mg/L residual
- if gas is used-6 hour contact time
- if hypochlorite is used-24 contact time
- residual is reduced to 2mg/L following contact time
complete fill method
all surfaces that may contact water are coated with a 200 mg/L chlorine solution
- minimum contact time of 30 min and then tank is filled to the overflow pipe
surface spray method
fill storage tank to 5% of total capacity
- add chlorine to bring residual to 50mg/L for at least 6 hours
- fill tank to overflow level with chlorinated water and hold for 24 hrs
- residual must be at least 2 mg/L after 24 hrs
partial fill method
