CWS Residential Water Quality Testing 2

Question 1

Which parameter is MOST commonly tested to assess microbiological safety in residential well water?

Accepted Answer

Total coliform bacteria

Answer

Total coliform bacteria is the primary indicator organism used to assess microbiological contamination in well water.

Question 2

A homeowner's water test shows a pH of 6.1. Which problem is MOST likely associated with this result?

Accepted Answer

Corrosion of copper plumbing

Answer

A pH of 6.1 is acidic and promotes corrosion of copper and other metal plumbing components.

Question 3

What is the EPA's Maximum Contaminant Level (MCL) for nitrate in drinking water, expressed as nitrogen?

Accepted Answer

10 mg/L

Answer

The EPA MCL for nitrate (as nitrogen) is 10 mg/L, primarily to protect infants from methemoglobinemia.

Question 4

Which test method is used to detect E. coli specifically in water samples?

Accepted Answer

Most probable number (MPN) with confirmatory testing

Answer

The MPN method with confirmatory testing (or membrane filtration) differentiates E. coli from other coliforms using enzyme-based substrates.

Question 5

A water sample collected in a sterile bottle is held at room temperature for 48 hours before testing. How does this affect coliform results?

Accepted Answer

Coliform counts may be falsely elevated

Answer

Warm holding temperatures allow bacteria to multiply, potentially producing falsely elevated coliform counts.

(CWS) Certified Water Specialist Practice Test