Virginia Wastewater Operator Class 2 License Exam 2026/2027 | Complete Study Guide with Practice Questions & Verified Answers – Pass Your VA Class 2 Wastewater Certification on the First Try

Virginia Wastewater Operator Class 2
License Exam 2026/2027 | Complete Study
Guide with Practice Questions & Verified
Answers – Pass Your VA Class 2 Wastewater
Certification on the First Try
VIRGINIA WASTEWATER OPERATOR CLASS 2 LICENSE EXAM 2026/2027 |
COMPLETE STUDY GUIDE

DOCUMENT OVERVIEW:

• This comprehensive study material provides 200 practice questions organized by
topic to help you master all essential concepts covered on the VA Class 2
Wastewater Operator Certification Exam — study systematically through each
section to build confidence and exam readiness.

• Each question includes five answer options with detailed rationales explaining
why the correct answer is right and why alternatives are incorrect — this approach
reinforces understanding and ensures you're prepared for similar questions on test
day.



SECTION 1: WASTEWATER TREATMENT FUNDAMENTALS



Question 1

Which of the following best describes the primary purpose of primary
wastewater treatment?

A) To remove dissolved organic compounds through biological oxidation

B) To remove settleable solids and some floatables through physical separation

C) To destroy pathogenic organisms using chemical disinfection

D) To convert ammonia into nitrate through nitrification

E) To reduce total suspended solids to below 5 mg/L permanently

,CORRECT ANSWER: B) To remove settleable solids and some floatables
through physical separation

Rationale: Primary treatment relies on physical processes where wastewater flows
through settling tanks (primary clarifiers) allowing heavier solids to settle to the
bottom (sludge) while lighter materials float to the top (scum). This process typically
removes 40-60% of suspended solids and about 25-35% of biochemical oxygen
demand (BOD). Option A describes secondary treatment (biological), Option C
describes disinfection/tertiary treatment, Option D describes nitrification
(secondary treatment), and Option E sets an unrealistic permanent standard since
treatment is continuous.



Question 2

What is the main function of secondary wastewater treatment?

A) Removal of grit and sand using screening and settling

B) Reduction of biodegradable organic matter through biological processes

C) Elimination of all nitrogen and phosphorus compounds

D) Disinfection of effluent before discharge

E) Recovery of metals and valuable minerals from sludge

CORRECT ANSWER: B) Reduction of biodegradable organic matter through
biological processes

Rationale: Secondary treatment uses microorganisms (bacteria, protozoa) to
oxidize biodegradable organic matter, reducing BOD by 80-90%. This is
accomplished through processes like activated sludge, trickling filters, or lagoons.
Option A is primary treatment, Option C is advanced treatment (not always
required), Option D is disinfection/tertiary treatment, and Option E is not a primary
objective of secondary treatment.



Question 3

,Which type of bacteria is primarily responsible for removing BOD in the
activated sludge process?

A) Nitrifying bacteria

B) Heterotrophic bacteria

C) Autotrophic bacteria

D) Methanogenic bacteria

E) Sulfate-reducing bacteria

CORRECT ANSWER: B) Heterotrophic bacteria

Rationale: Heterotrophic bacteria use organic matter (BOD) as both their carbon
source and energy source, oxidizing it to CO2 and H2O while growing and
reproducing. Nitrifying bacteria oxidize ammonia (autotrophic), methanogenic
bacteria produce methane in anaerobic conditions, and sulfate-reducing bacteria
reduce sulfates. These other organisms play different roles in treatment but
heterotrophs are the primary BOD-removing organisms.



Question 4

What is the purpose of the return activated sludge (RAS) in a conventional
activated sludge system?

A) To increase the hydraulic retention time in the clarifier

B) To introduce fresh microorganisms into the aeration basin

C) To return settling microorganisms to the aeration basin to maintain biomass
concentration

D) To remove excess nitrogen before discharge

E) To increase dissolved oxygen levels in the effluent

CORRECT ANSWER: C) To return settling microorganisms to the aeration basin
to maintain biomass concentration

, Rationale: Return activated sludge (RAS) is pumped from the secondary clarifier
back to the aeration basin to maintain an adequate mixed liquor suspended solids
(MLSS) concentration (typically 2,000-3,500 mg/L). This recycle of the active biomass
is critical for continued biological treatment. Excess RAS is wasted as waste
activated sludge (WAS) to maintain the desired sludge age.



Question 5

In a treatment plant influent, what does BOD (Biochemical Oxygen Demand)
measure?

A) The total amount of all organic compounds in the water

B) The amount of oxygen required by microorganisms to oxidize biodegradable
organic matter

C) The concentration of dissolved oxygen in the wastewater

D) The rate at which oxygen is transferred into the aeration basin

E) The toxicity level of chemical pollutants in wastewater

CORRECT ANSWER: B) The amount of oxygen required by microorganisms to
oxidize biodegradable organic matter

Rationale: BOD measures the amount of oxygen (in mg/L) consumed by
microorganisms during the decomposition of organic matter over a specified time
period (typically 5 days at 20°C, denoted as BOD5). It indicates the biodegradability
of wastewater. Option A is too broad (includes non-biodegradable organics), Option
C measures dissolved oxygen not demand, Option D measures oxygen transfer rate
not demand, and Option E measures toxicity.



Question 6

What is the difference between BOD and COD in wastewater treatment?

A) BOD measures only soluble organics while COD measures only suspended
organics