WASTEWATER

By Rick Lallish

What type of activated sludge treatment process is used when the influent is considered nutrient deficient?

A. Kraus process

B. Al West method

C. Membrane bioreactors

D. High-purity oxygen

Answer:  A. The Kraus process is used when the wastewater is nutrient deficient or has a greater ratio of carbonaceous to nitrogenous materials. This is usually found in dairy or cannery operations. It is a modification of a conventional activated sludge process and uses a portion of the anaerobic digester supernatant to supplement the nutrients needed for the activated sludge process. Other benefits of the Kraus process are increased sludge settleability and a ready supply of organisms. More information may be found in the CSU-Sacramento textbook: Operation of Wastewater Treatment Plants, Volume 1, Eighth edition, Chapter 5.

DRINKING WATER

By Drew Hoelscher

What type of joint would not be used in buried distribution system piping?

A. Push-on joint

B. Flanged joint

C. Mechanical joint

D. Welded joint

Answer: B. Many types of materials are used in water distribution systems, and that means many types of joints for connecting pipe. Flanged joints are most often used where piping is above grade. Flanged joints are not typically found in buried pipe due to the lack of flexing, in case the ground experiences shifting.

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.