WASTEWATER

By Rick Lallish

Which laboratory glassware is the most accurate means of delivering a measure of volume?

A. Graduated cylinder

B. Burette

C. Pipette

D. Beaker

Answer: C. There are many ways of delivering a volume of liquid in laboratory operations, but the most accurate tool is the pipette. There are two types: the graduated (or Mohr) and the serological. They are similar except the tips are different. Graduated cylinders are more accurate than beakers but not as precise as pipettes. Pipettes are drawn by suction; using your mouth is not recommended.  More information may be found in the CSU-Sacramento textbook: Operation of Wastewater Treatment Plants, Volume 1, Eighth edition, Chapter 9.

DRINKING WATER

By Drew Hoelscher

An operator is instructed to prepare a total coliform analysis for process control. At what temperature should the incubator be set?

A. 20 ± 0.5 degrees C

B. 25 ± 0.5 degrees C

C. 35 ± 0.5 degrees C

D. 40 ± 0.5 degrees C

Answer: C. Total coliform bacteria is an indicator to help determine the quality of the water in the distribution system. In addition to compliance-related samples, total coliform bacteria can be analyzed for process control instances, and operators should be aware of the incubation process. In short, the sample is prepared and incubated at 35 ± 0.5 degrees C for approximately 24 hours. When coliform bacteria are present, they will ferment the added sugars and cause the sample to appear more yellow.

About the author(s)

Rick Lallish is water pollution control program director and Drew Hoelscher is program director of drinking water operations at the Environmental Resources Training Center of Southern Illinois University Edwardsville.