WASTEWATER
By Rick Lallish
What is the greatest threat to wastewater lagoons or pond dikes?
A. Warm overcast days
B. Riprap coverage
C. Trees and shrubs
D. Burrowing animals
Answer: D. The largest reason for dike collapse is burrowing animals. Trees and shrubs do weaken the integrity of the dike, just not to the same extent. The animals create underground dens in the sides of dikes, weakening the dike massively, and without warning the dike will collapse and cause lagoon failure. Making the dike unattractive to the animals, trapping (with permission), and raising and lowering water levels over extended periods are established means of deterrence. Daily inspections and good housekeeping, such as increased mowing, are essential to maintaining lagoons and ponds. More information may be found in the WEF textbook Wastewater Treatment Fundamentals 1: Liquid Treatment, Chapter 6.
DRINKING WATER
By Drew Hoelscher
How does lubricant water pass between the sealing faces of a mechanical seal when the pump is designed for low pressure and low rpm?
A. The use of a balanced seal
B. The use of an unbalanced seal
C. Mechanical seals do not allow water to pass between the sealing faces
D. Adjusting the packing gland controls the flow of lubricant water between the sealing faces
Answer: B. Mechanical seals separate the wet end from the dry end on a pump and motor configuration. Water passes between the faces of a mechanical seal to promote cooling and lubrication. The water passing between the faces is unnoticed by the operator because the amount is so small that it evaporates. An unbalanced seal allows water to pass between the faces of a seal under low pressure and low rpm conditions, whereas a balanced seal allows water to pass between the faces under high pressure and high rpm.
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.
