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 topic of Internal Process Equipment; and Reverse Osmosis Chemicals. This time, you can test your knowledge about barscreen maintenance, and surface water characteristics.
Wastewater Treatment Sample Question:
What should be provided with an automatically cleaned mechanical barscreen to allow inspection and maintenance when the mechanical barscreen is designed and built?
A) An up-to-date sales catalog with the barscreen model pictured
B) A lock out/tag out (LOTO) kit
C) A spare motor
D) A manually cleaned bypass screen
Answer: Certainly a LOTO kit is very important toward safe inspection and maintenance activities of any piece of equipment at a wastewater treatment facility, but the best answer to this quiz question is D, a manually cleaned bypass screen. This completely separate barscreen could be located in a channel near the automated units. When thorough mechanical barscreen inspection, extended maintenance or emergency bypass must be initiated, the gates or valves to the manually cleaned screen can be opened and the influent flow would pass through the screen. The individual bars of the manually cleaned screens are normally wider spaced than their mechanical counterparts, which does allow more debris to pass through. Running a manual screen for long periods of time can allow more rags and large debris to accumulate further into the treatment plant, building up on mixer shafts, inside pumps and pipelines.
Water Treatment Sample Question:
What condition is defined by surface waters warming rapidly, expanding and becoming lighter than lower, colder waters?
A) Thermal overload
B) Thermal stratification
C) Thermocline
D) Hypolimnion
Answer: The answer is B, thermal stratification. Thermal stratification in a reservoir can make the depth selection of an acceptable raw water source difficult for the operator of the surface water treatment plant. Warmer water near the surface can harbor algae causing taste, odor and pH issues. Colder waters near the anaerobic bottom of the reservoir may contain hydrogen sulfide gas, and contribute to iron and manganese problems.
Thermal stratification may occur seasonally in some reservoirs, commonly with the start of the summer season. The layering effect of thermal stratification can be minimized by various methods including bubbler type aeration, mechanical mixers and/or mechanical aeration units. The prevention of stratification helps create a more homogenous blend of raw source water, which in turn can make the overall operation of the water treatment plant more consistent with respect to chemical dosing and finished water quality.
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.
