Exam Study Guide: Disinfection Byproducts; and Waste Brine Disposal

Maintaining your education is important, especially in a career that demands licensing exams. Prove you’re an expert operator by answering these questions and others from our Exam Study Guide Series.

Welcome back to TPO magazine's Exam Study Guide Series, which offers a pair of water/wastewater study questions with in-depth explanations of the answers. Last time, we covered a set of wastewater and drinking water treatment questions on the topics of Activated Sludge Bacteria; and Properties of Chlorine. This time, you can test your knowledge about 

Wastewater Treatment Sample Question:

Which of the following is an acid that is formed when chlorine gas is dissolved into a water supply used for disinfection?

A. Acetic acid

B. Hydrofluosilicic acid

C. Hypochlorous acid

D. Sulfamic acid

Answer: When chlorine gas is pulled into a chlorine ejector under the vacuum formed by the flowing water through the venturi within that ejector, it rapidly dissolves in the water. As it dissolves, it forms two acids: hypochlorous (HOCl) and hydrochloric (HCl) acids. Therefore, the answer is C. 

Depending on the water pH, temperature and a few other factors, the hypochlorous acid can convert to the hypochlorite ion (OCl-) and free hydrogen ion (H+). It is still a strong disinfectant, and it’s believed by many experts that it is the free available oxygen radical atom that does the job of oxidizing the pathogen’s cell membrane which essentially kills the cell. As the hypochlorous acid continues to decompose, it becomes chloride (Cl-) and free hydrogen (H+) that combine with other elements to form other compounds.

Water Treatment Sample Question:

The disposal of waste brine from an ion exchange softener can be difficult to dispose of.  The spent brine is classified as what type of waste product?

A. Toxic waste

B. Hazardous waste

C. Domestic waste

D. Industrial waste

Answer: The answer is D, industrial waste. The waste brine flowing from the ion exchange softener should be handled properly and disposed of in an environmentally friendly way. Most often, the waste flows into a sanitary sewer for treatment at a municipal wastewater treatment plant.

The brine can be high in conductivity, TDS and salinity which can be a shock to the bacteria in the wastewater treatment facility. If the wastewater plant discharges to a surface water body, it will most likely have a NPDES permit from the EPA. NPDES is the abbreviation for National Pollutant Discharge Elimination System, a special permit to discharge effluent into waters of the United States.

It is considered industrial waste and may fall under a municipality's industrial pretreatment program if it could cause interruption of service to the wastewater treatment facility.


About the author: Ron Trygar is the senior training specialist for water and wastewater programs at the University of Florida's TREEO Center. Previously, he was the wastewater process control specialist at Hillsborough County Public Utilities in Tampa, Florida. He has worked in the wastewater industry for more than 30 years in a variety of locations and positions. Trygar became a Certified Environmental Trainer (CET) in 1998 and has since provided training for associations and regulatory agencies such as Florida Department of Environmental Protection (FDEP); Florida Water and Pollution Control Operators Association Short Schools; USABlueBook; Florida Water Environment Association sponsored training events; and local school environmental programs. Working alongside the FDEP Northeast District, Trygar helped begin the Florida Rural Water Association and FDEP joint operator certification review classes that are still given around the state today. He holds a Florida Class A wastewater treatment operator’s license and a Florida Class B drinking water operator’s license.



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