Wastewater Operator Certification Disinfection Processes 2

Question 1

At what approximate wavelength does UV radiation most effectively inactivate microorganisms?

Accepted Answer

254 nm

Answer

185 nm

Answer

320 nm

Answer

400 nm

Question 2

What is the primary mechanism by which UV disinfection inactivates microorganisms?

Accepted Answer

Damaging DNA and RNA, preventing reproduction

Answer

Oxidizing and rupturing the cell membrane

Answer

Denaturing key structural proteins

Answer

Disrupting the cell wall synthesis

Question 3

Which effluent quality parameter most significantly limits UV disinfection performance?

Accepted Answer

Turbidity and UV transmittance (UVT)

Answer

Dissolved oxygen concentration

Answer

Water temperature

Answer

Total dissolved solids

Question 4

A major operational advantage of UV disinfection over chlorination is:

Accepted Answer

No chemical residual or formation of harmful disinfection byproducts

Answer

Lower capital equipment costs

Answer

Greater effectiveness against all protozoan cysts

Answer

Simple monitoring with no specialized equipment

Question 5

Why must ozone (O₃) used for disinfection be generated on-site?

Accepted Answer

It is an unstable gas that decomposes rapidly and cannot be stored

Answer

It is prohibitively expensive to transport

Answer

Federal regulations prohibit off-site ozone production

Answer

It reacts violently with water during transport

Question 6

Against which pathogen does UV disinfection have a significant advantage over conventional chlorination?

Accepted Answer

Cryptosporidium parvum oocysts

Answer

Escherichia coli

Answer

Salmonella typhi

Answer

Fecal streptococci

Question 7

What is the primary operational disadvantage of ozone disinfection compared to chlorination for wastewater reuse applications?

Accepted Answer

Ozone provides no persistent residual disinfection after treatment

Answer

Ozone is less effective at inactivating bacteria

Answer

Ozone requires a higher pH to function

Answer

Ozone generates more regulated disinfection byproducts