WASTEWATER
By Rick Lallish
During a visual inspection of the activated sludge aeration basin, you notice that a stiff white foam has formed on the surface. What is the most probable condition?
A. Young sludge or underloaded system
B. Filamentous overloading
C. Polymer overdosing
D. Older sludge or overloaded system
Answer: A. The formation of stiff white foam on the aeration basin is typical of young sludge or an underloaded system. The food-to-microorganism ratio is most likely very high and the mean cell residence time is extremely low. Microscopic observation will show flagellates and amoeba as the highest populations, and the MLSS is very low. This is normal on plant startup, or after the bacterial population has been killed off due to shock loading or toxic conditions and is recovering. Measures to correct this condition are to reduce or stop any wasting, adjust the return activated sludge to build an acceptable blanket in the secondary clarifier, and move the sludge to the aeration basin. More information may be found in the OWP, CSU-Sacramento textbook: Operation of Wastewater Treatment Plants (Eighth Edition), Chapter 5.
DRINKING WATER
By Drew Hoelscher
PFAS chemicals found in some drinking water sources are what kind of compounds?
A. Synthetic organic compounds (SOCs)
B. Volatile organic compounds (VOCs)
C. Inorganic compounds (IOCs)
D. Radionuclides
Answer: A. PFAS substances are SOCs used in many manufacturing practices. These substances are very stable and do not naturally degrade over time. PFAS are being monitored in drinking water supplies throughout the United States so that a better understanding can be developed.
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.
