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 Bacterial Functions; and Water Filtration Processes. This time, you can test your knowledge about centrifugal pumps, and cloudy source water.
Wastewater Treatment Sample Question:
Which of the choices listed below is a typical application for a centrifugal pump?
A) Belt press drain sump and reclaimed water high service
B) Thickened belt press sludge feed and dewatered cake conveyance
C) Composite sampler and aluminum sulfate feed
D) Centrifuge cake discharge and primary sludge feed to anaerobic digester
Answer: The answer is A, belt press drain sump and reclaimed water high service. Since the liquids presented in answer choice A are normally very thin, with low solids content, centrifugal pumps work well in these applications. The fluids presented in answers B, C and D are usually more viscous, with higher total solids content. Positive displacement pumps are well-suited for these applications. Answer choice C lists composite sampler and aluminum sulfate feed. These choices are normally pumped using either a peristaltic pump or a diaphragm chemical metering pump, which are types of positive displacement type pumps, and can be set to very accurate flow rates.
Water Treatment Sample Question:
The cloudy appearance of a source water that is caused by the presence of suspended and colloidal matter is known as ________ ?
A) Total hardness
B) Turbidity
C) Conductivity
D) Total dissolved solids (TDS)
Answer: Turbidity that creates cloudiness of a source water is produced from very finely divided suspended organic and inorganic particles, so the answer is B. These particles can be from silt or clay found in river, stream or lake water supplies. Algae and bacteria can also cause turbidity, but can also be pathogenic and must be removed or inactivated.
Colloidal matter found within a source water supply will normally not settle or precipitate out from the liquid due to their electrical charge. Colloidal particles are similar to magnets, which is when two similar magnetic poles are near each other, they tend to always repel each other. If the turbidity is caused by colloidal particles that are similar in electrical charge, they will not allow themselves to join together into larger, heavier particles.
A jar test performed in the water laboratory will indicate to the operator which coagulant chemical will work best to neutralize the electrical charge of the colloidal particles and allow these destabilized particles to join together into larger flocs that will settle.
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.
