AWWA Water Quality Testing 3

Question 1

Which organism is used as an indicator for fecal contamination in distribution system monitoring under the Total Coliform Rule?

Accepted Answer

Escherichia coli

Answer

E. coli is the definitive fecal indicator; its presence in a distribution sample triggers immediate investigation and public notification requirements.

Question 2

What is the Maximum Contaminant Level (MCL) for total trihalomethanes (TTHMs) in a community water system?

Accepted Answer

80 µg/L

Answer

EPA's Stage 2 Disinfectants and Disinfection Byproducts Rule sets the MCL for TTHMs at 80 µg/L as a locational running annual average.

Question 3

A water sample shows high UV absorbance at 254 nm (UVA254). What does this indicate?

Accepted Answer

Elevated natural organic matter (NOM) concentration

Answer

UV absorbance at 254 nm is a surrogate measure of aromatic natural organic matter, which is a precursor to disinfection byproduct formation.

Question 4

Which disinfection method is most effective at inactivating Cryptosporidium oocysts in drinking water?

Accepted Answer

Ultraviolet (UV) irradiation

Answer

Cryptosporidium oocysts are highly resistant to chemical disinfectants, but UV irradiation at adequate doses effectively inactivates them by damaging their DNA.

Question 5

What is the purpose of heterotrophic plate count (HPC) testing in drinking water?

Accepted Answer

Assess general microbial quality and treatment effectiveness

Answer

HPC measures the total culturable bacteria in water and serves as an indicator of overall microbiological quality and the adequacy of treatment and distribution system maintenance.

(AWWA) American Water Works Association Practice Test

(AWWA) American Water Works Association Practice Test

AWWA Water Quality Testing 3