Minnesota Subsurface Sewage
Treatment System Basic Installer Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. The primary purpose of a subsurface sewage treatment system (SSTS)
is to:
A. Store wastewater permanently underground
B. Transport wastewater directly to surface water
C. Treat and disperse wastewater safely into the soil
D. Eliminate the need for plumbing systems
Correct answer: C. Treat and disperse wastewater safely into the soil
The purpose of an SSTS is to provide treatment and safe dispersal of
wastewater while protecting groundwater and public health.
, 2. In Minnesota, an SSTS installer must understand soil characteristics
because soil:
A. Determines the color of septic tanks
B. Controls treatment and absorption capacity
C. Prevents all wastewater movement
D. Replaces the need for system design
Correct answer: B. Controls treatment and absorption capacity
Soil properties such as texture, structure, and permeability determine how
effectively wastewater can be treated and dispersed.
3. The septic tank primarily functions to:
A. Disinfect all wastewater
B. Pump wastewater continuously
C. Settle solids and provide anaerobic treatment
D. Remove all nutrients from wastewater
Correct answer: C. Settle solids and provide anaerobic treatment
A septic tank allows solids to settle, scum to rise, and anaerobic bacteria to
partially treat wastewater before discharge to the soil treatment area.
4. The layer of floating material in a septic tank is called:
,A. Sludge
B. Effluent
C. Scum
D. Biomass
Correct answer: C. Scum
Scum consists mainly of fats, oils, and lighter solids that float on the
wastewater surface in the tank.
5. The solids that settle at the bottom of a septic tank are called:
A. Sludge
B. Scum
C. Effluent
D. Filtrate
Correct answer: A. Sludge
Sludge accumulates at the bottom of the tank and must be removed
through regular pumping.
6. A soil treatment area is designed to:
A. Store untreated sewage
B. Provide biological treatment and dispersal
, C. Replace septic tanks
D. Increase wastewater flow
Correct answer: B. Provide biological treatment and dispersal
The soil treatment area uses soil microorganisms and physical processes to
treat effluent before it reaches groundwater.
7. The biomat in a soil treatment system forms:
A. On the bottom of the septic tank
B. At the soil trench interface
C. Inside the building sewer
D. Around the pump motor
Correct answer: B. At the soil trench interface
A biomat is a biological layer that develops where effluent contacts soil
and contributes to treatment and flow control.
8. Excessive loading of a soil treatment area may cause:
A. Improved treatment
B. Faster groundwater recharge only
C. System failure and surfacing sewage
D. Complete removal of solids
Correct answer: C. System failure and surfacing sewage
Treatment System Basic Installer Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. The primary purpose of a subsurface sewage treatment system (SSTS)
is to:
A. Store wastewater permanently underground
B. Transport wastewater directly to surface water
C. Treat and disperse wastewater safely into the soil
D. Eliminate the need for plumbing systems
Correct answer: C. Treat and disperse wastewater safely into the soil
The purpose of an SSTS is to provide treatment and safe dispersal of
wastewater while protecting groundwater and public health.
, 2. In Minnesota, an SSTS installer must understand soil characteristics
because soil:
A. Determines the color of septic tanks
B. Controls treatment and absorption capacity
C. Prevents all wastewater movement
D. Replaces the need for system design
Correct answer: B. Controls treatment and absorption capacity
Soil properties such as texture, structure, and permeability determine how
effectively wastewater can be treated and dispersed.
3. The septic tank primarily functions to:
A. Disinfect all wastewater
B. Pump wastewater continuously
C. Settle solids and provide anaerobic treatment
D. Remove all nutrients from wastewater
Correct answer: C. Settle solids and provide anaerobic treatment
A septic tank allows solids to settle, scum to rise, and anaerobic bacteria to
partially treat wastewater before discharge to the soil treatment area.
4. The layer of floating material in a septic tank is called:
,A. Sludge
B. Effluent
C. Scum
D. Biomass
Correct answer: C. Scum
Scum consists mainly of fats, oils, and lighter solids that float on the
wastewater surface in the tank.
5. The solids that settle at the bottom of a septic tank are called:
A. Sludge
B. Scum
C. Effluent
D. Filtrate
Correct answer: A. Sludge
Sludge accumulates at the bottom of the tank and must be removed
through regular pumping.
6. A soil treatment area is designed to:
A. Store untreated sewage
B. Provide biological treatment and dispersal
, C. Replace septic tanks
D. Increase wastewater flow
Correct answer: B. Provide biological treatment and dispersal
The soil treatment area uses soil microorganisms and physical processes to
treat effluent before it reaches groundwater.
7. The biomat in a soil treatment system forms:
A. On the bottom of the septic tank
B. At the soil trench interface
C. Inside the building sewer
D. Around the pump motor
Correct answer: B. At the soil trench interface
A biomat is a biological layer that develops where effluent contacts soil
and contributes to treatment and flow control.
8. Excessive loading of a soil treatment area may cause:
A. Improved treatment
B. Faster groundwater recharge only
C. System failure and surfacing sewage
D. Complete removal of solids
Correct answer: C. System failure and surfacing sewage
