Exam Study Guide: Types of Liquid Waste; and Colloidal Particles in Water

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 Industrial Waste Treatment; and Backflow Control Devices. This time, you can test your knowledge about the different types of liquid waste, and colloidal particles in water.

Wastewater Treatment Sample Question

What is the term used to describe domestic wastewater from septic tanks, porta-johns, RVs or cesspools?

A. Industrial waste
B. Mobile active waste
C. Leachate
D. Septage

Answer: The answer to the question is D. Septage is normally brought to the treatment facility in tanker trucks. It is generally much higher strength than domestic wastewater, and can overload smaller waste treatment facilities. Grease trap waste is not considered septage and should not be accepted in waste treatment facilities due to different regulations. Knowledge of the different types of waste and characteristics help the operator identify problems before they occur.

Water Treatment Sample Question

What is the term used to describe the electrostatic repulsion between colloidal particles in water?

A. Coagulation
B. Zeta potential
C. Tuberculation
D. Van Der Waals force

Answer: The correct answer is B. The majority of colloidal particles in water carry a slightly negative charge, which allows the particles to repel one another. This repulsion stabilizes the particles, which means they will not settle out of solution. The higher the zeta potential (measured in mV) the more stable and less likely the colloids are to aggregate and form a cluster. As the zeta potential nears zero the colloidal particles will coagulate and flocculate rapidly.

About the authors: Rick Lallish is the Water Pollution Control program director at the Environmental Resources Training Center (ERTC) of Southern Illinois University Edwardsville. He provides training for entry-level operators in the wastewater field and operators throughout the state looking to further their education. Lallish was also named the 2017 Illinois Operator of the Year and 2018 president of the Illinois Association of Water Pollution Control Operators.

Drew Hoelscher is the program director of drinking water operations at the Environmental Resources Training Center in Edwardsville, Illinois.


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