WASTEWATER

By Rick Lallish

What superior disinfection process is created on site, is done in an enclosed tank, and produces off-gas that must be destroyed before release to the atmosphere?

A. Ozonation

B. Chlorine

C. Peracetic acid

D. Ultraviolet radiation

Answer: A. The ozonation process involves the creation of ozone by feeding oxygen through electrodes (6,000-20,000 volts). This creates ozone, which can be used as disinfectant. The gas is highly unstable, but when dosed properly, it is very efficient at disinfecting wastewater effluent of bacteria, viruses, protozoa and other microorganisms as well as some contaminants of emerging concern. However, the off-gas is extremely hazardous and must be destroyed or recycled before any release to the atmosphere. More information may be found in the WEF textbook Wastewater Treatment Fundamentals III: Advanced Treatment, Chapter 5.

DRINKING WATER

By Drew Hoelscher

An operator uses a nonionic polymer as a filter aid. Under optimum operating conditions, what dosage would be considered normal?

A. 0.1 mg/L

B. 1.0 mg/L

C. 10 mg/L

D. 15 mg/L

Answer: A. To reduce the risk of turbidity breakthrough, operators may dose the filter influent with a high-molecular-weight polymer. Usually, polymers fed as a filter aid are nonionic or slightly anionic. The polymer helps strengthen the bonds between the particles and helps coat the filter media. To prevent reaching terminal headloss too quickly, operators should dose the filter aid at about 0.1 mg/L.

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.