Wastewater industrial pretreatment practice questions
20 free practice questions from 40 CFR Part 403. Each answer is explained and linked to the rule it comes from.
Wastewater industrial pretreatment
20 questions across 7 topics. After each answer you see why it is right, with a link to the official source.
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Scope and key definitions
1. Under 403.3(e), Best Management Practices are schedules of activities, prohibitions of practices, maintenance procedures and other management practices to implement which prohibitions?
- A. The conditions for the Upset defense in 403.16
- B. The prohibitions listed in 403.5(a)(1) and (b)
- C. The record retention rules in 403.12(o)
- D. The removal credit conditions in 403.7
Show answer
Answer: B. The prohibitions listed in 403.5(a)(1) and (b)
403.3(e) defines Best Management Practices as "schedules of activities, prohibitions of practices, maintenance procedures, and other management practices to implement the prohibitions listed in § 403.5(a)(1) and (b)." It adds that "BMPs also include treatment requirements, operating procedures, and practices to control plant site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw materials storage."
2. Under 403.3(v)(3), on what finding may the Control Authority determine that an Industrial User meeting the criteria in 403.3(v)(1)(ii) is not a Significant Industrial User?
- A. A finding that the User has paid all of its sewer use charges
- B. A finding that the User has installed a flow meter at its sampling point
- C. A finding that the POTW has a design flow of 5 mgd or less
- D. A finding that the User has no reasonable potential for adversely affecting the POTW's operation or for violating any Pretreatment Standards or requirement
Show answer
Answer: D. A finding that the User has no reasonable potential for adversely affecting the POTW's operation or for violating any Pretreatment Standards or requirement
"Upon a finding that an Industrial User meeting the criteria in paragraph (v)(1)(ii) of this section has no reasonable potential for adversely affecting the POTW's operation or for violating any Pretreatment Standards or requirement, the Control Authority may at any time, on its own initiative or in response to a petition received from an Industrial User or POTW", make that determination.
3. Under 403.3(v)(2), which of these is one of the conditions for the Control Authority to find that an Industrial User subject to categorical Pretreatment Standards is a Non-Significant Categorical Industrial User?
- A. The Industrial User never discharges any untreated concentrated wastewater
- B. The Industrial User discharges only to a POTW with a design flow of 5 mgd or less
- C. The Industrial User has a slug control plan approved by the Approval Authority
- D. The Industrial User samples its Discharge every operating day
Show answer
Answer: A. The Industrial User never discharges any untreated concentrated wastewater
The finding requires that the User "never discharges more than 100 gallons per day (gpd) of total categorical wastewater" and meets the listed conditions: it "has consistently complied with all applicable categorical Pretreatment Standards and Requirements", "annually submits the certification statement required in § 403.12(q)", and "never discharges any untreated concentrated wastewater."
Prohibited discharges and local limits
4. To whom do the general prohibitions in 403.5(a)(1) and the specific prohibitions in 403.5(b) apply?
- A. Only Significant Industrial Users
- B. Only Industrial Users subject to categorical Pretreatment Standards
- C. Each User introducing pollutants into a POTW, whether or not the User is subject to other National Pretreatment Standards or any national, State, or local Pretreatment Requirements
- D. Only New Sources that began construction after proposed standards were published
Show answer
Answer: C. Each User introducing pollutants into a POTW, whether or not the User is subject to other National Pretreatment Standards or any national, State, or local Pretreatment Requirements
The prohibitions "apply to each User introducing pollutants into a POTW whether or not the User is subject to other National Pretreatment Standards or any national, State, or local Pretreatment Requirements."
Source: eCFR: 40 CFR 403.5, National pretreatment standards: Prohibited discharges (as of Nov 4, 2026)
5. Under 403.5(b)(5), who may approve alternate temperature limits instead of the 40 °C (104 °F) limit at the POTW Treatment Plant, and on whose request?
- A. The Industrial User, upon its own determination
- B. The POTW, upon request of the Industrial User
- C. The Approval Authority, upon request of the POTW
- D. Any member of the public, upon petition to the POTW
Show answer
Answer: C. The Approval Authority, upon request of the POTW
Heat is prohibited so that the temperature at the POTW Treatment Plant does not exceed 40 °C (104 °F) "unless the Approval Authority, upon request of the POTW, approves alternate temperature limits."
Source: eCFR: 40 CFR 403.5, National pretreatment standards: Prohibited discharges (as of Nov 4, 2026)
6. Under 403.5(c)(2), when must a POTW that is not developing a POTW Pretreatment Program develop and enforce specific effluent limits?
- A. In cases where pollutants contributed by User(s) result in Interference or Pass-Through, and such violation is likely to recur
- B. Whenever any new Industrial User connects to the sewer
- C. Only when an Industrial User asks the POTW to set limits
- D. Only when the POTW's design flow reaches 5 mgd
Show answer
Answer: A. In cases where pollutants contributed by User(s) result in Interference or Pass-Through, and such violation is likely to recur
"All other POTW's shall, in cases where pollutants contributed by User(s) result in Interference or Pass-Through, and such violation is likely to recur, develop and enforce specific effluent limits".
Source: eCFR: 40 CFR 403.5, National pretreatment standards: Prohibited discharges (as of Nov 4, 2026)
7. How does 403.5(c)(4) treat Best Management Practices that a POTW develops to implement its specific limits?
- A. They are voluntary guidance that cannot be enforced
- B. They replace the general prohibitions in 403.5(a)(1)
- C. They apply only to Users that are not subject to any categorical standard
- D. They are considered local limits and Pretreatment Standards for the purposes of Part 403 and section 307(d) of the Act
Show answer
Answer: D. They are considered local limits and Pretreatment Standards for the purposes of Part 403 and section 307(d) of the Act
"Such BMPs shall be considered local limits and Pretreatment Standards for the purposes of this part and section 307(d) of the Act."
Source: eCFR: 40 CFR 403.5, National pretreatment standards: Prohibited discharges (as of Nov 4, 2026)
Categorical Pretreatment Standards
8. What does 403.6(b) require New Sources to do with all pollution control equipment required to meet applicable Pretreatment Standards?
- A. Install it within 3 years of the date the Standard is effective
- B. Install it, have it in operating condition, and "start-up" it before beginning to Discharge
- C. Install it only after the Control Authority finds a violation
- D. Install it within 180 days after beginning to Discharge
Show answer
Answer: B. Install it, have it in operating condition, and "start-up" it before beginning to Discharge
"New Sources shall install and have in operating condition, and shall “start-up” all pollution control equipment required to meet applicable Pretreatment Standards before beginning to Discharge."
Source: eCFR: 40 CFR 403.6, National pretreatment standards: Categorical standards (as of Nov 4, 2026)
9. Section 403.6(d) prohibits dilution as a substitute for treatment. What does it say the Control Authority may impose on Industrial Users which are using dilution to meet applicable Pretreatment Standards or Requirements?
- A. Mass limitations
- B. Removal credits
- C. Fundamentally different factors variances
- D. A waiver of the categorical Pretreatment Standard
Show answer
Answer: A. Mass limitations
"The Control Authority may impose mass limitations on Industrial Users which are using dilution to meet applicable Pretreatment Standards or Requirements, or in other cases where the imposition of mass limitations is appropriate."
Source: eCFR: 40 CFR 403.6, National pretreatment standards: Categorical standards (as of Nov 4, 2026)
10. Under 403.6(e)(4), when may an Industrial User change the monitoring points it uses to determine compliance?
- A. At any time, as long as it notes the change in its next periodic report
- B. After giving the Regional Administrator 10 days' notice
- C. Only after receiving approval from the Control Authority
- D. At the start of each new control mechanism term without approval
Show answer
Answer: C. Only after receiving approval from the Control Authority
"The Industrial User may change monitoring points only after receiving approval from the Control Authority."
Source: eCFR: 40 CFR 403.6, National pretreatment standards: Categorical standards (as of Nov 4, 2026)
POTW pretreatment programs
11. Under 403.8(a), who may require a POTW with a design flow of 5 mgd or less to develop a POTW Pretreatment Program?
- A. Any Significant Industrial User discharging to the POTW
- B. The POTW's largest Industrial User, by petition
- C. The State hazardous waste authority, on any finding
- D. The Regional Administrator or Director, if he or she finds that the nature or volume of the industrial influent, treatment process upsets, violations of POTW effluent limitations, contamination of municipal sludge, or other circumstances warrant
Show answer
Answer: D. The Regional Administrator or Director, if he or she finds that the nature or volume of the industrial influent, treatment process upsets, violations of POTW effluent limitations, contamination of municipal sludge, or other circumstances warrant
"The Regional Administrator or Director may require that a POTW with a design flow of 5 mgd or less develop a POTW Pretreatment Program if he or she finds that" the listed circumstances "warrant in order to prevent Interference with the POTW or Pass Through."
12. Under 403.8(f)(2)(vi), what are Significant Industrial Users required to do about changes at their facility affecting the potential for a Slug Discharge?
- A. Mention them in the next June or December periodic report
- B. Notify the POTW immediately
- C. Wait for the POTW's next annual inspection
- D. Notify the Regional Administrator within 90 days
Show answer
Answer: B. Notify the POTW immediately
"Significant Industrial Users are required to notify the POTW immediately of any changes at its facility affecting potential for a Slug Discharge."
13. For the annual public notification in 403.8(f)(2)(viii), a Significant Industrial User is in significant noncompliance if its violation meets one or more of the listed criteria. Which other Industrial Users does that sentence also name?
- A. Any Industrial User which violates paragraphs (f)(2)(viii)(A) or (B)
- B. Only Industrial Users subject to categorical Pretreatment Standards
- C. None; the sentence names Significant Industrial Users only
- D. Any Industrial User which violates paragraphs (f)(2)(viii)(C), (D), or (H)
Show answer
Answer: D. Any Industrial User which violates paragraphs (f)(2)(viii)(C), (D), or (H)
"For the purposes of this provision, a Significant Industrial User (or any Industrial User which violates paragraphs (f)(2)(viii)(C), (D), or (H) of this section) is in significant noncompliance if its violation meets one or more of the following criteria".
Industrial User reports and notices
14. Under 403.12(g)(2), the Control Authority performed the sampling and analysis in lieu of the Industrial User, the results show a violation, and resampling is required. Who must perform the repeat sampling and analysis?
- A. The Control Authority, unless it notifies the User of the violation and requires the User to perform the repeat analysis
- B. The Industrial User in every case
- C. The Approval Authority
- D. No one, because a sample taken by the Control Authority is never repeated
Show answer
Answer: A. The Control Authority, unless it notifies the User of the violation and requires the User to perform the repeat analysis
"Where the Control Authority has performed the sampling and analysis in lieu of the Industrial User, the Control Authority must perform the repeat sampling and analysis unless it notifies the User of the violation and requires the User to perform the repeat analysis."
Source: eCFR: 40 CFR 403.12, Reporting requirements for POTW's and industrial users (as of Nov 4, 2026)
15. Under 403.12(f), which Industrial Users must notify the POTW immediately of all discharges that could cause problems to the POTW, including any slug loadings?
- A. Only Significant Industrial Users
- B. Only Industrial Users subject to categorical Pretreatment Standards
- C. All categorical and non-categorical Industrial Users
- D. Only Industrial Users with a slug control plan
Show answer
Answer: C. All categorical and non-categorical Industrial Users
"All categorical and non-categorical Industrial Users shall notify the POTW immediately of all discharges that could cause problems to the POTW, including any slug loadings".
Source: eCFR: 40 CFR 403.12, Reporting requirements for POTW's and industrial users (as of Nov 4, 2026)
16. Under 403.12(j), whom must all Industrial Users promptly notify in advance of any substantial change in the volume or character of pollutants in their Discharge?
- A. Only the EPA Regional Administrator
- B. The Control Authority (and the POTW if the POTW is not the Control Authority)
- C. Only the State hazardous waste authorities
- D. The public, through a newspaper notice
Show answer
Answer: B. The Control Authority (and the POTW if the POTW is not the Control Authority)
"All Industrial Users shall promptly notify the Control Authority (and the POTW if the POTW is not the Control Authority) in advance of any substantial change in the volume or character of pollutants in their Discharge".
Source: eCFR: 40 CFR 403.12, Reporting requirements for POTW's and industrial users (as of Nov 4, 2026)
17. Under 403.12(g)(3), where may multiple grab samples for volatile organics and oil & grease, collected during a 24-hour period, be composited prior to the analysis?
- A. In the laboratory
- B. In the field only
- C. In the field or in the laboratory, at the User's choice
- D. Nowhere; each grab sample must be analyzed separately
Show answer
Answer: A. In the laboratory
Multiple grab samples may be composited prior to the analysis as follows: "For cyanide, total phenols, and sulfides the samples may be composited in the laboratory or in the field; for volatile organics and oil & grease the samples may be composited in the laboratory."
Source: eCFR: 40 CFR 403.12, Reporting requirements for POTW's and industrial users (as of Nov 4, 2026)
Signatures, records and POTW reports
18. When does 403.12(o)(2) say the record retention period for Industrial Users and POTWs shall be extended?
- A. Whenever the Industrial User changes owners
- B. Whenever the POTW's NPDES permit expires
- C. Only when the Industrial User requests it
- D. During the course of any unresolved litigation regarding the Industrial User or POTW, or when requested by the Director or the Regional Administrator
Show answer
Answer: D. During the course of any unresolved litigation regarding the Industrial User or POTW, or when requested by the Director or the Regional Administrator
"This period of retention shall be extended during the course of any unresolved litigation regarding the Industrial User or POTW or when requested by the Director or the Regional Administrator."
Source: eCFR: 40 CFR 403.12, Reporting requirements for POTW's and industrial users (as of Nov 4, 2026)
Upset and bypass
19. Under 403.16(c)(3), to whom must an Industrial User that wishes to establish the affirmative defense of Upset have submitted the required information about the Upset?
- A. Only the EPA Regional Administrator
- B. Only the State hazardous waste authorities
- C. The POTW and Control Authority
- D. The public, through a newspaper notice
Show answer
Answer: C. The POTW and Control Authority
The Industrial User must show it "has submitted the following information to the POTW and Control Authority within 24 hours of becoming aware of the Upset", with a written submission within five days if given orally.
Source: eCFR: 40 CFR 403.16, Upset provision (as of Nov 4, 2026)
20. Under 403.17(d)(2), after considering its adverse effects, what must the Control Authority determine before it may approve an anticipated bypass by an Industrial User?
- A. That the bypass will last less than 24 hours
- B. That the bypass will meet the three conditions listed in 403.17(d)(1)
- C. That the POTW Treatment Plant has spare treatment capacity
- D. That the Industrial User has published notice of the bypass in a newspaper
Show answer
Answer: B. That the bypass will meet the three conditions listed in 403.17(d)(1)
"The Control Authority may approve an anticipated bypass, after considering its adverse effects, if the Control Authority determines that it will meet the three conditions listed in paragraph (d)(1) of this section." The first condition is that the "Bypass was unavoidable to prevent loss of life, personal injury, or severe property damage"; the others are no feasible alternatives and the required notices.