Wastewater Treatment Operator Certification Practice Exam #2 2023 with 100% correct answers

What is true about chlorine gas? It is 2.5 times heavier than air What is the typical BOD removal efficiency in a primary clarifier? 20 to 50% What does the "F" in F/M ratio represent? The food for the microorganisms flowing into the aeration tank, in lbs/day What describes the appearance of healthy activated sludge? Brown with a moderate amount of crisp, white foam What is used to control filamentous organisms? Chlorine What are commonly used to control chlorine feed rate for disinfection? Flow and chlorine residual Which toxic gas is commonly found in septic wastewater and smells like rotten eggs? Hydrogen sulfide What is the permissible exposure limit for chlorine gas vapor during a normal 8-hour workday and a 40-hour workweek? 0.5 ppm What is a vulnerability assessment? Contingency planning to determine the vulnerability of the utility during various types of emergencies and identify corrective actions to reduce the risks What is the difference between the settling rate of activated sludge and raw sludge? Activated sludge settles slower than raw sludge What should be mostly found in healthy activated sludge? Free-swimming and stalked ciliates One to two percent of the digester gas in an anaerobic digester consists of: Hydrogen, nitrogen, hydrogen sulfide and other gases What is true during the colder winter months? Modify operations to increase solids under aeration to provide more microorganisms to treat the BOD What type of sludge would you expect in an aeration tank if the content is dark and has low DO? Septic sludge What could happen if the volatile acid/alkalinity ratio starts to increase, and corrective action is not taken immediately? Carbon dioxide content in the digester gas will increase What are screenings? Pieces of wood, roots, rags, and other large debris What happens when there is more food in the influent to the aeration tank? More oxygen is required in the aeration tank What impact does temperature have on the reaction rate of microorganisms in wastewater? Reaction rate doubles with every 18 degrees Fahrenheit increases in temperature until higher temperature inhibits biological activity What is commonly used to control the odor of hydrogen sulfide? Chlorine What is used to determine the amount of microorganisms in the aeration tank? Mixed liquor volatile suspended solids (MLVSS) What could happen if the sludge line is isolated by closing the valves on each end for several days? Gas production could increase the internal pressure and cause the line to fail What is typically treated by biological processes? Dissolved and non-settleable organic What document is a written record that accurately traces the custody of wastewater samples through all phases of monitoring program? Chain of custody form