WASTEWATER
By Rick Lallish
What type of pump should never be operated or started against a closed valve?
A. Centrifugal pump
B. Peripheral pump
C. Positive displacement pump
D. Screw lift pump
Answer: C. Basic operation and knowledge of pumps and pumping are fundamentals that wastewater operators should understand. Positive displacement pumps are ideally suited for the pumping of solids such as sludges. They are also well-suited for some chemical applications, such as polymers. Due to the tremendous pressure built up by the pump, a positive displacement pump must never be operated against a closed valve or in a dry condition for very long, or
