WTO Quality Monitoring 2

Question 1

What is the Maximum Contaminant Level (MCL) for total trihalomethanes (TTHMs) in drinking water under the Stage 2 Disinfectants and Disinfection Byproducts Rule?

Accepted Answer

0.080 mg/L

Answer

The MCL for TTHMs under the Stage 2 DBPR is 0.080 mg/L, calculated as a locational running annual average.

Question 2

A water system collects a bacteriological sample that tests positive for total coliform. What must the operator do next according to the Total Coliform Rule?

Accepted Answer

Notify the state within 24 hours and collect repeat samples

Answer

A positive total coliform result requires the operator to notify the state within 24 hours and collect repeat samples to determine if E. coli is present.

Question 3

Which parameter is measured using a turbidimeter and is critical for evaluating filter performance?

Accepted Answer

Turbidity

Answer

Turbidity, measured in NTU using a turbidimeter, indicates the cloudiness of water and is a key indicator of filter performance and microbial risk.

Question 4

Under the Surface Water Treatment Rule, what is the maximum turbidity limit for combined filter effluent (CFE) that cannot be exceeded more than 5% of the time in any month?

Accepted Answer

1 NTU

Answer

The SWTR allows CFE turbidity to exceed 1 NTU no more than 5% of measurements in any month, with an absolute limit of 5 NTU.

Question 5

What does a chlorine residual of zero in the distribution system most likely indicate?

Accepted Answer

Inadequate disinfection or excessive demand in the system

Answer

A zero chlorine residual suggests either insufficient disinfectant was applied or high chlorine demand from biofilm, sediment, or contaminants is consuming it.

(WTO) Water Treatment Operator Certification Practice Test

(WTO) Water Treatment Operator Certification Practice Test

WTO Quality Monitoring 2