Equipment Operation, Maintenance, and Troubleshooting Flashcards
7 cards from real Wastewater Operator Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Equipment Operation, Maintenance, and Troubleshooting flashcards as text
What is the most common cause of cavitation in a centrifugal pump?
Answer: Suction lift is too high
Cavitation occurs when the liquid pressure at the pump inlet drops below its vapor pressure, causing vapor bubbles to form and then collapse violently. An excessively high suction lift (the vertical distance the pump must pull water) is a primary cause of this pressure drop, leading to noise, vibration, and damage to the impeller.
During routine maintenance on a positive displacement pump, what is a critical check to prevent poor performance and leaks?
Answer: Inspecting seals and packing for wear
Positive displacement pumps rely on tight tolerances to move fluid. Worn seals and packing are a common source of leaks and loss of efficiency. Regularly inspecting and replacing them as needed is a critical preventive maintenance task.
An operator notices a floating sludge blanket in a secondary clarifier. What is the most likely cause?
Answer: Denitrification occurring in the sludge blanket
A floating sludge blanket is often caused by denitrification. In this process, bacteria in the sludge convert nitrates to nitrogen gas, and the gas bubbles attach to sludge flocs, causing them to rise to the surface. This typically indicates that the sludge has been in the clarifier for too long (high sludge age).
Which of the following is a primary indicator that a pump's bearings are failing?
Answer: Excessive heat and vibration
Failing bearings generate excess friction, which manifests as heat and high-frequency vibrations. An unusually hot bearing housing or a noticeable increase in noise or vibration are classic signs that the bearings are worn and need replacement.
What is the primary purpose of a Lockout/Tagout (LOTO) procedure?
Answer: To isolate equipment from energy sources during maintenance
Lockout/Tagout is a critical safety procedure used to ensure that dangerous equipment is properly shut off and not able to be started up again prior to the completion of maintenance or repair work. It is designed to protect workers from hazardous energy releases.
If the dissolved oxygen (DO) level in an aeration basin is consistently low despite the blowers operating normally, what is a likely cause?
Answer: The air diffusers are clogged or fouled
Diffusers are the components that release air from the blowers into the wastewater. Over time, they can become clogged with biological growth or mineral scale, which reduces their ability to transfer oxygen efficiently. This leads to low DO levels even when the blowers are functioning correctly.
A mechanical bar screen repeatedly shuts down on high torque. What is the most probable cause?
Answer: Excessive debris or rags accumulating on the screen
Mechanical bar screens are designed to remove large debris from the influent. An accumulation of heavy or bulky materials like rags, wood, or plastics can jam the rake mechanism, causing the motor to draw high amperage and shut down on a torque or overload fault. This indicates a need for cleaning or that the plant is receiving an unusual amount of debris.