Exam Study Guide


By Rick Lallish

What will happen if you lose vacuum to the feed line on a chlorinator?

A. Water feed to the chlorinator will be lost.

B. Excess chlorine will be drawn from the cylinder.

C. The chlorinator will close, stopping gas flow.

D. Nothing will happen; the chlorinator will run normally.

Answer: C. Basic operation of a vacuum-based chlorine gas system is a fundamental that operators need to understand. Most chlorinators operate under a vacuum condition at the injector from the chlorinator. Understanding how this process works will help in troubleshooting chlorinator and disinfection problems. According to the Water Environment Federation Wastewater Treatment Fundamentals 1 – Liquid Treatment textbook, “The injector creates a vacuum that pulls chlorine gas from the chlorinator and into the water being treated. If a leak develops anywhere between the chlorinator and the injector, air will be pulled into the line. Loss of vacuum causes the chlorinator to close, stopping the flow of gas from the cylinder or container.”


By Drew Hoelscher

What types of pumps typically feed chemical solutions at a potable water treatment plant?

A. End-suction centrifugal or split-case pumps

B. Jet or split-case pumps

C. Peristaltic or diaphragm pumps

D. Dynamic or centrifugal pumps

Answer: C. Peristaltic pumps and diaphragm pumps are positive displacement pumps that can maintain constant and steady flow rates, regardless of changing head pressure or fluid viscosity. Peristaltic pumps move fluid by a spinning rotor with several rollers that isolate a section of tube or hose as they rotate. The fluid contained in the isolated section advances to the discharge end of the pump by the rollers’ continuous motion. Diaphragm pumps move fluid using a reciprocating diaphragm. The back-and-forth linear motion of the diaphragm allows fluid to enter and exit the pump head assembly.

About the author

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. 


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