WTO Water Quality & Treatment Principles 3

Question 1

Which pathogen is most resistant to chlorine disinfection and requires UV or ozone treatment for effective inactivation?

Accepted Answer

Cryptosporidium parvum

Answer

Cryptosporidium parvum oocysts are highly resistant to chlorine disinfection; UV light or ozone are required for effective inactivation.

Question 2

What does the term 'breakthrough' indicate during granular activated carbon (GAC) filtration?

Accepted Answer

When the GAC media has reached its adsorption capacity and contaminants pass through

Answer

Breakthrough occurs when the GAC bed is exhausted and can no longer adsorb contaminants, allowing them to pass through into the finished water.

Question 3

Which of the following best describes 'hardness' in water?

Accepted Answer

The concentration of dissolved calcium and magnesium ions

Answer

Water hardness is caused primarily by dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions, and is typically expressed as mg/L of calcium carbonate equivalent.

Question 4

What is the purpose of a residual disinfectant maintained in a drinking water distribution system?

Accepted Answer

To provide ongoing protection against microbial regrowth and contamination

Answer

A disinfectant residual in the distribution system provides a continuing barrier against microbial contamination and regrowth as water travels to consumers.

Question 5

In a conventional treatment plant, what is the correct order of treatment processes?

Accepted Answer

Coagulation → Flocculation → Sedimentation → Filtration → Disinfection

Answer

The conventional treatment sequence is coagulation, flocculation, sedimentation, filtration, and then disinfection to produce safe drinking water.

(WTO) Water Treatment Operator Certification Practice Test

(WTO) Water Treatment Operator Certification Practice Test

WTO Water Quality & Treatment Principles 3