OTCO BASIC WASTEWATER PRACTICE EXAM
2026/2027: 200 VERIFIED QUESTIONS &
ANSWERS WITH DETAILED RATIONALES FOR
OPERATOR CERTIFICATION SUCCESS
OTCO Basic Wastewater Practice Exam –
Questions and ☑VERIFIED ANSWERs
Section 1: Treatment Process Fundamentals
Q1: What is the main purpose of a wastewater
treatment plant?
A. Provide drinking water
B. Remove contaminants to protect health and
the environment
C. Produce fertilizer
D. Generate energy
☑VERIFIED ANSWER: B
Rationale: The primary objective of wastewater
,treatment is to remove pollutants from sewage
to prevent environmental pollution and protect
public health, ensuring treated effluent meets
regulatory standards before discharge.
Q2: Which process is used first in most
wastewater plants?
A. Aeration
B. Screening
C. Disinfection
D. Sludge digestion
☑VERIFIED ANSWER: B
Rationale: Screening is the first physical
treatment step that removes large debris like
rags, sticks, and plastics to protect downstream
equipment (pumps, valves) from damage and
clogging, allowing subsequent processes to
function efficiently.
,Q3: What does BOD measure?
A. Biological Oxygen Demand – oxygen used by
microbes to decompose organic matter
B. Base Oxygen Density
C. Biochemical Oxidation Degree
D. Basic Oxygen Demand
☑VERIFIED ANSWER: A
Rationale: Biochemical Oxygen Demand (BOD)
indicates the amount of dissolved oxygen that
microorganisms need to break down organic
pollutants in wastewater. It is a key measure of
organic strength.
Q4: What is TSS?
A. Total Suspended Solids – particles suspended
in water
B. Total Salt Solution
, C. Total Sulfate Standard
D. Total Soluble Substances
☑VERIFIED ANSWER: A
Rationale: Total Suspended Solids (TSS)
measures the concentration of solid particles
that are not dissolved but remain suspended in
the water column. Elevated TSS in effluent
indicates poor solids removal.
Q5: What is the main purpose of a grit
chamber?
A. Remove heavy inorganic solids like sand and
gravel
B. Remove dissolved organics
C. Disinfect water
D. Measure flow rate
☑VERIFIED ANSWER: A
Rationale: Grit chambers are designed to
2026/2027: 200 VERIFIED QUESTIONS &
ANSWERS WITH DETAILED RATIONALES FOR
OPERATOR CERTIFICATION SUCCESS
OTCO Basic Wastewater Practice Exam –
Questions and ☑VERIFIED ANSWERs
Section 1: Treatment Process Fundamentals
Q1: What is the main purpose of a wastewater
treatment plant?
A. Provide drinking water
B. Remove contaminants to protect health and
the environment
C. Produce fertilizer
D. Generate energy
☑VERIFIED ANSWER: B
Rationale: The primary objective of wastewater
,treatment is to remove pollutants from sewage
to prevent environmental pollution and protect
public health, ensuring treated effluent meets
regulatory standards before discharge.
Q2: Which process is used first in most
wastewater plants?
A. Aeration
B. Screening
C. Disinfection
D. Sludge digestion
☑VERIFIED ANSWER: B
Rationale: Screening is the first physical
treatment step that removes large debris like
rags, sticks, and plastics to protect downstream
equipment (pumps, valves) from damage and
clogging, allowing subsequent processes to
function efficiently.
,Q3: What does BOD measure?
A. Biological Oxygen Demand – oxygen used by
microbes to decompose organic matter
B. Base Oxygen Density
C. Biochemical Oxidation Degree
D. Basic Oxygen Demand
☑VERIFIED ANSWER: A
Rationale: Biochemical Oxygen Demand (BOD)
indicates the amount of dissolved oxygen that
microorganisms need to break down organic
pollutants in wastewater. It is a key measure of
organic strength.
Q4: What is TSS?
A. Total Suspended Solids – particles suspended
in water
B. Total Salt Solution
, C. Total Sulfate Standard
D. Total Soluble Substances
☑VERIFIED ANSWER: A
Rationale: Total Suspended Solids (TSS)
measures the concentration of solid particles
that are not dissolved but remain suspended in
the water column. Elevated TSS in effluent
indicates poor solids removal.
Q5: What is the main purpose of a grit
chamber?
A. Remove heavy inorganic solids like sand and
gravel
B. Remove dissolved organics
C. Disinfect water
D. Measure flow rate
☑VERIFIED ANSWER: A
Rationale: Grit chambers are designed to
