WASTEWATER

By Rick Lallish

When conducting a sludge settleometer test, what does the first 5 minutes of the test indicate?

A. Presence of filaments

B. Particle collision rate

C. Presence of zoogloeal matter

D. No useful indication

Answer: D. The settled sludge volume after 5 minutes of settling in the settleometer is an indication of how fast the sludge is settling. The first 5 minutes the sludge is in a free-fall state, with only a few collisions of floc particles to slow it down (Eckenfelder and Melbinger, 1957). This is in a typical settleometer analysis, and there may be a few exceptions. This will help operators or lab personnel understand the process and how to read the results. More information may be found in the WEF Manual, Activated Sludge and Nutrient Removal, Third Edition, Chapter 4. 

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DRINKING WATER

By Drew Hoelscher

What public notification is triggered if a water system exceeds the nitrate MCL?

A. Tier 1

B. Tier 2

C. Tier 3

D. Tier 4

Answer: A. The public notification rule is intended to keep customers informed about the safety of their water in a timely manner. Depending on the severity of the issue, a system is legally responsible to notify customers within certain time periods. A Tier 1 notification is considered the highest threat and must be delivered within 24 hours. A few examples of a Tier 1 occurrence would be fecal/E.coli contamination, chlorine dioxide MRDL violation and/or exceedance of the maximum allowable turbidity level, resulting in an MCL violation.

About the authors

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.