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

0.040 mg/L

Answer

0.060 mg/L

Answer

0.100 mg/L

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

Immediately issue a boil-water advisory

Answer

Collect repeat samples within 24 hours

Answer

Shut down the distribution system

Question 3

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

Accepted Answer

Turbidity

Answer

pH

Answer

Hardness

Answer

Alkalinity

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

0.3 NTU

Answer

5 NTU

Answer

0.5 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

Over-chlorination at the treatment plant

Answer

The system uses chloramine instead of free chlorine

Answer

The meter needs recalibration

Question 6

Which method is the EPA-approved reference method for measuring free chlorine residual in drinking water?

Accepted Answer

DPD colorimetric method

Answer

Colorimetric method using OTO

Answer

Iodometric titration

Answer

Starch-iodide method

Question 7

A water system monitoring for lead under the Lead and Copper Rule collects first-draw samples from household taps. How long must water stagnate in the plumbing before sample collection?

Accepted Answer

At least 6 hours

Answer

At least 2 hours

Answer

At least 30 minutes

Answer

At least 8 hours