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Wastewater Treatment Basic Operations > Disinfection > Flashcards

Disinfection Flashcards

1
Q

What are the three typical forms of pathogens?

A

Bacteria
Viruses
Parasites

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2
Q

What are some examples of diseases caused by bacteria in wastewater?

A 
Salmonellosis
Shigellosis
Typhoid fever
Cholera
Paratyphoid
Dysentery
Anthrax
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3
Q

What is disinfection?

A

Getting rid of disease causing organisms

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4
Q

What can be used as an indicator of effectiveness of disinfection?

A

Fecal coliforms. They are only found in the small intestine of warm blooded animals and can show cross-contamination

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5
Q

What is UV disinfection?

A

Mercury lamps produce UV light that damages the nucleic acids of microorganisms which prevent reproduction

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6
Q

What is UV dose?

A

A product of UV intensity and residence time

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7
Q

What is UV transmittance?

A

The ratio of light entering and exiting the water

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8
Q

What are some water considerations for UV?

A

Hardness can foul quartz sleeves

pH can effect clarity due to soluble metal

Suspended solids negatively effect clarity

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9
Q

What is solarization in UV?

A

The quartz sleeve will get dimmer over time

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10
Q

Advantages of UV disinfection

A

Short detention time (5-7 seconds)
No toxic byproducts
No residual

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11
Q

What are disadvantages of UV?

A

High energy demand
No residual
Use of mercury

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12
Q

What is ozone?

A

An extremely strong oxidant; triatomic oxygen

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13
Q

How much energy applied goes to the generation of ozone?

A

About 10%

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14
Q

Advantages of ozone

A

High oxidation potential and more reactive than chlorine

Less persistent residuals

Fewer byproducts

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15
Q

Disadvantages of ozone

A

High capital, operation, and maintenance cost

Corrosive

Safety hazard

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16
Q

How does chlorine react with water?

A

It produces hypochlorous acid and hydrochloric acid

Hypochlorous acid is a strong disinfectant whereas hydrochloric acid is nothing special

17
Q

How does hypochlorous acid break down?

A

Into hydrogen and the hypochlorite ion

The amount of breakdown is dependent on pH; higher pH means more hypochlorite

18
Q

What is calcium hypochlorite?

A

Granular

Contains 65% chlorine by weight

Added to water gives you hypochlorous acid and lime

19
Q

What is sodium hypochlorite?

A

Clear to greenish yellow liquid

10-15% strength

Added to water makes hypochlorous acid and sodium hydroxide

20
Q

What is a consideration with the breakdown of sodium hypochlorite over time?

A

The strength is reduced as it is stored, so dosages may need to be adjusted

21
Q

How does chlorine react with other substancez?

A

It can be reduced by reducing agents, resulting in the production of chloramines

22
Q

What is chlorine dose?

A

Demand + residual

23
Q

Which chloramines can be used for disinfection?

A

Mono and dichloramines, and they have a persistent residual

24
Q

How does pH affect the formation of chloramines?

A

<4 will be trichloramines

4-5.5 will be dichloramines

6.5-7.5 mono and di will exist together

25
Q

What is the difference between hypochlorinators and chlorinators?

A

Hypochlorinators are used to inject in liquid

Chlorinators are used to inject gas

26
Q

What are safety considerations with chlorine cylinders?

A

Keep protective hood in place

Store away from heat

Store upright

Store secured to an immovable object

27
Q

Chlorine leak detection

A

An ammonia solution will emit white vapor, but this is toxic

28
Q

How to dechlorinate?

A 
Long detention times
Aeration
Sunlight 
Activated carbon
Sulfer dioxide (1:1) basis
29
Q

What is a chlorine residual?

A

The concentration of chlorine present in water after the demand has been satisfied

30
Q

What are some examples of diseases caused by viruses in wastewater?

A

Polio

Infectious hepatitis

31
Q

What are some examples of diseases cause by parasites in wastewater?

A

Amoebic dysentery
Ascaris
Giardiasis
Cryptosporidium is

Wastewater Treatment Basic Operations (16 decks)

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