WASTEWATER

By Rick Lallish

When using 1-ton chlorine cylinders, where is the connection made to remove liquid chlorine?

A. Top valve

B. Bottom valve

C. Either the top or bottom valve

D. Both the top and bottom valves

Answer: B. When using 1-ton chlorine cylinders, you connect the flexible tubing to the evaporator to the bottom valve to remove the liquid chlorine. If you want to remove the chlorine as a gas, you make the connection at the top valve. Care must be taken to place the cylinder in the proper orientation with the valves in the up and down positions. Chlorine gas is extremely hazardous, and proper care and operation of chlorine equipment is a vital safety measure. More information may be found in the OWP, CSU-Sacramento textbook Operation of Wastewater Treatment Plants, Volume 1, Eighth Edition, Chapter 7.  

DRINKING WATER

By Drew Hoelscher

What is the maximum concentration limit (MCL) for combined radium 226 and 228 isotopes?

A. 5 pCi/L

B. 15 ppm

C. 10 mg/L

D. 30 ppb

Answer: A. The radionuclide final rule was published in 2000 to improve public health. If combined radium 226 and 228 isotopes are detected, it is most likely due to the water source coming from a deep bedrock aquifer. Certain rock formations contain naturally occurring radionuclides that eventually dissolve into the source water. To ensure that the water is safe from radioactive contamination, systems collect samples at the distribution system entry point.

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.