FREE Wastewater Operator Activated Sludge Fundamentals Questions and Answers

Question 1

Which of the following is the primary purpose of the aeration basin in an activated sludge system?

Accepted Answer

To provide an environment for microorganisms to oxidize organic matter.

Answer

To allow for the settling of biological floc.

Answer

To remove inorganic suspended solids.

Answer

To equalize flow and pollutant loading.

Question 2

An operator observes that the activated sludge in the aeration basin is dark brown, has a pleasant earthy odor, and settles well in a jar test. This typically indicates:

Accepted Answer

A healthy, well-functioning activated sludge.

Answer

An over-aerated system with excessive nitrification.

Answer

A system experiencing filamentous bulking.

Answer

A condition of septic sludge due to insufficient oxygen.

Question 3

What is the primary role of the secondary clarifier in an activated sludge process?

Accepted Answer

To separate the biological floc (activated sludge) from the treated wastewater.

Answer

To introduce air into the wastewater for microbial growth.

Answer

To remove grit and other inorganic solids.

Answer

To disinfect the effluent before discharge.

Question 4

Which operational parameter is typically adjusted to control the amount of biomass in an activated sludge system and maintain a desired Mean Cell Residence Time (MCRT)?

Accepted Answer

Waste Activated Sludge (WAS) flow rate.

Answer

Influent flow rate.

Answer

Return Activated Sludge (RAS) flow rate.

Answer

Aeration blower speed.

Question 5

A sudden increase in the Sludge Volume Index (SVI) in an activated sludge plant often indicates:

Accepted Answer

Poor settling characteristics of the activated sludge.

Answer

An increase in the concentration of suspended solids in the effluent.

Answer

A decrease in the organic loading to the plant.

Answer

Improved settling and denser sludge.

Question 6

What is the primary function of Return Activated Sludge (RAS) in the activated sludge process?

Accepted Answer

To reintroduce active microorganisms from the secondary clarifier back into the aeration basin.

Answer

To waste excess biomass from the system.

Answer

To dilute the influent wastewater entering the aeration basin.

Answer

To provide additional oxygen to the aeration basin.