Residential Water Quality Testing Flashcards

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

Answer: Total coliform bacteria

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

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

Answer: Corrosion of copper plumbing

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

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

Answer: 10 mg/L

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

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

Answer: Most probable number (MPN) with confirmatory testing

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

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

Answer: Coliform counts may be falsely elevated

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

Which type of residential water sample is submitted in a sodium thiosulfate-treated bottle?

Answer: Bacteriological sample from a chlorinated source

Sodium thiosulfate neutralizes residual chlorine, preventing it from killing bacteria during transit to the lab.

What does a turbidity reading of 5 NTU in untreated well water MOST likely indicate?

Answer: Possible sediment, microorganisms, or surface water intrusion

Elevated turbidity in well water suggests suspended particles, which may include sediment, microorganisms, or infiltration of surface water.