Biological Treatment Practice Questions for Level 1 · Entry

1. Question 1

   What does an aeration diffuser do?

   1. Measure pressure inside the air header
   2. Open and close airflow to the basin
   3. Release air as bubbles into wastewater
   4. Remove moisture from the blower intake
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   Answer: C. Release air as bubbles into wastewater

   A diffuser releases compressed air as bubbles into wastewater, allowing oxygen to transfer into the water.

2. Question 2

   How does a rotating biological contactor operate?

   1. Discs rotate through wastewater and air
   2. Discs remain submerged without rotating
   3. Biomass circulates through an empty tank
   4. Wastewater bypasses the biological discs
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   Answer: A. Discs rotate through wastewater and air

   An RBC slowly rotates biological discs through wastewater and air so attached microorganisms contact both the wastewater and oxygen.

3. Question 3

   What does return activated sludge carry back to the aeration basin?

   1. Grit removed at the headworks
   2. Settled biological solids
   3. Disinfected final effluent
   4. Primary scum and grease
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   Answer: B. Settled biological solids

   Return activated sludge moves settled biological solids from the secondary clarifier back to the aeration basin.

4. Question 4

   Why is some activated sludge removed from the treatment process?

   1. Supply oxygen to the biological solids
   2. Return settled solids to the aeration basin
   3. Keep all biological solids in the process
   4. Control the amount and age of biological solids
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   Answer: D. Control the amount and age of biological solids

   Microorganisms grow as they treat wastewater. Removing excess activated sludge keeps the biological-solids inventory and sludge age under control.

5. Question 5

   Which description best explains the activated sludge process to a new operator?

   1. Air and microorganisms treat wastewater in an aeration basin, and settling then separates the microorganisms
   2. Air alone removes the wastes in an aeration basin, and filters return the separated solids to the incoming sewer
   3. Microorganisms grow only on the basin walls, and the mixed wastewater leaves without settling the organisms
   4. Most treatment occurs in the clarifier, while the aeration basin mainly stores flow
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   Answer: A. Air and microorganisms treat wastewater in an aeration basin, and settling then separates the microorganisms

   In activated sludge, air supports microorganisms mixed with wastewater, and a clarifier then settles those organisms from the treated water. For example, the aeration basin is like a feeding and mixing area, while the clarifier is the separation area. B gives air the biological job, C describes attached growth and skips settling, and D reverses the roles of the basin and clarifier.

Operator Master has 12 Level 1 · Entry biological treatment questions, free.

• Plant Operations54 questions
• Math and Calculations50 questions
• Laboratory13 questions
• Safety13 questions
• Disinfection10 questions
• Pumps and Hydraulics8 questions
• Regulations and Compliance8 questions
• Solids Handling8 questions
• Primary Treatment6 questions
• Secondary Clarification5 questions
• Grit Removal4 questions
• Headworks and Screening4 questions