Wastewater biosolids use and disposal practice questions
20 free practice questions from 40 CFR Part 503 Subparts A, B, C and E. Each answer is explained and linked to the rule it comes from.
Wastewater biosolids use and disposal
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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General provisions
1. 503.5(b) states that nothing in Part 503 precludes whom from imposing more stringent or additional requirements for the use or disposal of sewage sludge?
- A. Only the person who prepares the sewage sludge
- B. A State or political subdivision thereof or interstate agency
- C. Only the owner of the land where sewage sludge is applied
- D. Only a POTW's industrial users
Show answer
Answer: B. A State or political subdivision thereof or interstate agency
"Nothing in this part precludes a State or political subdivision thereof or interstate agency from imposing requirements for the use or disposal of sewage sludge more stringent than the requirements in this part or from imposing additional requirements for the use or disposal of sewage sludge."
Source: eCFR: 40 CFR 503.5, Additional or more stringent requirements (as of Nov 4, 2026)
2. What does 503.6(b) say about choosing how sewage sludge is used or disposed?
- A. EPA selects the practice for each treatment works
- B. Land application must be chosen wherever it is feasible
- C. Incineration must be chosen for sludge from POTWs that serve 10,000 people or more
- D. Part 503 does not require the selection of a practice; the manner of use or disposal is a local determination
Show answer
Answer: D. Part 503 does not require the selection of a practice; the manner of use or disposal is a local determination
"This part does not require the selection of a sewage sludge use or disposal practice. The determination of the manner in which sewage sludge is used or disposed is a local determination."
3. Under 503.4, what must any person who prepares sewage sludge that is disposed in a municipal solid waste landfill unit ensure?
- A. That the sewage sludge meets the requirements in 40 CFR part 258 concerning the quality of materials disposed in a municipal solid waste landfill unit
- B. That the sewage sludge meets the Class A pathogen requirements in 503.32(a)
- C. That the sewage sludge meets the pollutant concentrations in Table 3 of 503.13
- D. That the sewage sludge is covered with soil at the end of each operating day under 503.33(b)(11)
Show answer
Answer: A. That the sewage sludge meets the requirements in 40 CFR part 258 concerning the quality of materials disposed in a municipal solid waste landfill unit
Disposal in a municipal solid waste landfill unit "that complies with the requirements in 40 CFR part 258 constitutes compliance with section 405(d) of the CWA." The preparer "shall ensure that the sewage sludge meets the requirements in 40 CFR part 258 concerning the quality of materials disposed in a municipal solid waste landfill unit."
Source: eCFR: 40 CFR 503.4, Relationship to other regulations (as of Nov 4, 2026)
Definitions
4. Under 503.9(r), which of these is a person who prepares sewage sludge?
- A. A person who only hauls sewage sludge from the treatment works to a farm
- B. The owner of the land on which sewage sludge is applied
- C. The person who derives a material from sewage sludge
- D. The permitting authority that issues the sludge permit
Show answer
Answer: C. The person who derives a material from sewage sludge
"Person who prepares sewage sludge is either the person who generates sewage sludge during the treatment of domestic sewage in a treatment works or the person who derives a material from sewage sludge."
Source: eCFR: 40 CFR 503.9, General definitions (as of Nov 4, 2026)
5. Which activities does the 503.9(z) definition of treatment of sewage sludge name as included?
- A. Thickening, stabilization, and dewatering of sewage sludge
- B. Storage of sewage sludge on land for two years or less
- C. Placement of sewage sludge on a surface disposal site
- D. Application of bulk sewage sludge to agricultural land
Show answer
Answer: A. Thickening, stabilization, and dewatering of sewage sludge
"Treat or treatment of sewage sludge is the preparation of sewage sludge for final use or disposal. This includes, but is not limited to, thickening, stabilization, and dewatering of sewage sludge. This does not include storage of sewage sludge."
Source: eCFR: 40 CFR 503.9, General definitions (as of Nov 4, 2026)
Land application: applicability and general requirements
6. Under 503.10(b)(1), the general requirements in 503.12 and the management practices in 503.14 do not apply to land-applied bulk sewage sludge that meets the Table 1 ceiling concentrations, the Table 3 pollutant concentrations, one of the vector attraction reduction requirements in 503.33(b)(1) through (b)(8), and which pathogen requirements?
- A. The Class B pathogen requirements in 503.32(b)
- B. The domestic septage pathogen requirements in 503.32(c)
- C. No pathogen requirements
- D. The Class A pathogen requirements in 503.32(a)
Show answer
Answer: D. The Class A pathogen requirements in 503.32(a)
The exemption applies "if the bulk sewage sludge meets the ceiling concentrations in Table 1 of § 503.13 and the pollutant concentrations in Table 3 of § 503.13; the Class A pathogen requirements in § 503.32(a); and one of the vector attraction reduction requirements in § 503.33(b)(1) through (b)(8)."
Source: eCFR: 40 CFR 503.10, Applicability (as of Nov 4, 2026)
7. Under 503.12(d), the person who prepares bulk sewage sludge applied to agricultural land, forest, a public contact site or a reclamation site must give the applier written notification of what?
- A. The concentration of total nitrogen (as N on a dry weight basis) in the bulk sewage sludge
- B. The percent volatile solids reduction achieved
- C. The fecal coliform density of the sludge
- D. The total phosphorus concentration of the sludge
Show answer
Answer: A. The concentration of total nitrogen (as N on a dry weight basis) in the bulk sewage sludge
The preparer "shall provide the person who applies the bulk sewage sludge written notification of the concentration of total nitrogen (as N on a dry weight basis) in the bulk sewage sludge."
Source: eCFR: 40 CFR 503.12, General requirements (as of Nov 4, 2026)
8. Bulk sewage sludge subject to the cumulative pollutant loading rates has been applied to a site since July 20, 1993, and the cumulative amount of each pollutant applied since then is not known. What does 503.12(e)(2)(iv) say?
- A. The full cumulative amount in Table 2 may be applied to the site
- B. An additional amount of each pollutant shall not be applied to the site under 503.13(a)(2)(i)
- C. The applier may assume half of the Table 2 amount remains
- D. The amount may be estimated from records of nearby sites
Show answer
Answer: B. An additional amount of each pollutant shall not be applied to the site under 503.13(a)(2)(i)
When the cumulative amount "since that date is not known, an additional amount of each pollutant shall not be applied to the site in accordance with § 503.13(a)(2)(i)."
Source: eCFR: 40 CFR 503.12, General requirements (as of Nov 4, 2026)
Land application: pollutant limits and management practices
9. Under 503.13(a)(3), which limit applies to the pollutants in bulk sewage sludge applied to a lawn or a home garden?
- A. The cumulative pollutant loading rates in Table 2 of 503.13
- B. The annual pollutant loading rates in Table 4 of 503.13
- C. The concentrations in Table 2 of 503.23
- D. The concentration for each pollutant in Table 3 of 503.13
Show answer
Answer: D. The concentration for each pollutant in Table 3 of 503.13
"If bulk sewage sludge is applied to a lawn or a home garden, the concentration of each pollutant in the sewage sludge shall not exceed the concentration for the pollutant in Table 3 of § 503.13."
Source: eCFR: 40 CFR 503.13, Pollutant limits (as of Nov 4, 2026)
10. Under 503.14(e), which item must the label or information sheet for sewage sludge sold or given away in a bag or other container for application to the land contain?
- A. The name of the person who will apply the sewage sludge
- B. The fecal coliform density measured in the sewage sludge
- C. The annual whole sludge application rate that does not cause any of the annual pollutant loading rates in Table 4 of 503.13 to be exceeded
- D. The date on which the sewage sludge was put in the bag
Show answer
Answer: C. The annual whole sludge application rate that does not cause any of the annual pollutant loading rates in Table 4 of 503.13 to be exceeded
The label or information sheet must contain the name and address of the person who prepared the sewage sludge, a statement that application "is prohibited except in accordance with the instructions on the label or information sheet", and "The annual whole sludge application rate for the sewage sludge that does not cause any of the annual pollutant loading rates in Table 4 of § 503.13 to be exceeded."
Source: eCFR: 40 CFR 503.14, Management practices (as of Nov 4, 2026)
11. 503.14(d) requires bulk sewage sludge to be applied at a whole sludge application rate equal to or less than the agronomic rate. For which type of site may the permitting authority specify otherwise?
- A. A public contact site
- B. A reclamation site
- C. A forest
- D. Agricultural land
Show answer
Answer: B. A reclamation site
The rate must not exceed the agronomic rate "unless, in the case of a reclamation site, otherwise specified by the permitting authority."
Source: eCFR: 40 CFR 503.14, Management practices (as of Nov 4, 2026)
Land application: monitoring, records and reports
12. Under 503.16(b), when domestic septage applied to agricultural land, forest, or a reclamation site meets the pathogen requirements in 503.32(c)(2) or the vector attraction reduction requirements in 503.33(b)(12), what must be monitored for compliance with those requirements?
- A. One composite sample per 365 day period
- B. One container out of every ten applied
- C. Only the first container applied each month
- D. Each container of domestic septage applied to the land
Show answer
Answer: D. Each container of domestic septage applied to the land
In that case "each container of domestic septage applied to the land shall be monitored for compliance with those requirements."
Source: eCFR: 40 CFR 503.16, Frequency of monitoring (as of Nov 4, 2026)
13. Under 503.16(a)(2), after sewage sludge has been monitored for two years at the Table 1 frequency, who may reduce the frequency of monitoring for pollutant concentrations?
- A. The permitting authority
- B. The person who prepares the sewage sludge, on its own
- C. The person who applies the sewage sludge
- D. The owner or lease holder of the land
Show answer
Answer: A. The permitting authority
"After the sewage sludge has been monitored for two years at the frequency in Table 1 of § 503.16, the permitting authority may reduce the frequency of monitoring for pollutant concentrations" and for certain pathogen density requirements.
Source: eCFR: 40 CFR 503.16, Frequency of monitoring (as of Nov 4, 2026)
14. Under 503.18(b), what triggers reporting the applier's site information in 503.17(a)(5)(ii)(A) through (G) on February 19 of each year?
- A. Any exceedance of a Table 1 ceiling concentration
- B. A change in the person who applies the sludge
- C. 90 percent or more of any of the cumulative pollutant loading rates in Table 2 of 503.13 is reached at a land application site
- D. The sale of the land application site
Show answer
Answer: C. 90 percent or more of any of the cumulative pollutant loading rates in Table 2 of 503.13 is reached at a land application site
The information must be reported "on February 19th of each year when 90 percent or more of any of the cumulative pollutant loading rates in Table 2 of § 503.13 is reached at a land application site."
Surface disposal
15. Under 503.22(c), who must submit a written closure and post closure plan to the permitting authority before an active sewage sludge unit closes?
- A. The person who prepares the sewage sludge
- B. The subsequent owner of the site
- C. The owner/operator of the active sewage sludge unit
- D. A qualified ground-water scientist
Show answer
Answer: C. The owner/operator of the active sewage sludge unit
"The owner/operator of an active sewage sludge unit shall submit a written closure and post closure plan to the permitting authority 180 days prior to the date that the active sewage sludge unit closes."
Source: eCFR: 40 CFR 503.22, General requirements (as of Nov 4, 2026)
16. Under 503.24(l), on what condition may animals be grazed on an active sewage sludge unit?
- A. When the sewage sludge placed on the unit meets one of the Class B pathogen requirements
- B. When the owner/operator demonstrates to the permitting authority that, through management practices, public health and the environment are protected from reasonably anticipated adverse effects of pollutants in the sludge
- C. When the active sewage sludge unit has a liner and a leachate collection system
- D. When 30 days have passed since sewage sludge was last placed on the active sewage sludge unit
Show answer
Answer: B. When the owner/operator demonstrates to the permitting authority that, through management practices, public health and the environment are protected from reasonably anticipated adverse effects of pollutants in the sludge
"Animals shall not be grazed on an active sewage sludge unit, unless the owner/operator of the surface disposal site demonstrates to the permitting authority that through management practices public health and the environment are protected from any reasonably anticipated adverse effects of pollutants in sewage sludge when animals are grazed."
Source: eCFR: 40 CFR 503.24, Management practices (as of Nov 4, 2026)
17. Under 503.20(b), which sewage sludge is outside Subpart C (surface disposal)?
- A. Sewage sludge placed on an active sewage sludge unit with a liner and leachate collection system
- B. Sewage sludge placed on an active sewage sludge unit without a liner
- C. Sewage sludge placed on a surface disposal site that has a run-off collection system
- D. Sewage sludge stored on the land
Show answer
Answer: D. Sewage sludge stored on the land
"This subpart does not apply to sewage sludge stored on the land or to the land on which sewage sludge is stored."
Source: eCFR: 40 CFR 503.20, Applicability (as of Nov 4, 2026)
Incineration
18. Under 503.40(c), which gas must be monitored continuously in the exit gas from the incinerator stack, as one of the conditions for the total hydrocarbons management practice in 503.45(a) not to apply?
- A. Methane
- B. Nitrogen oxides
- C. Carbon monoxide
- D. Sulfur dioxide
Show answer
Answer: C. Carbon monoxide
One condition is that "The exit gas from a sewage sludge incinerator stack is monitored continuously for carbon monoxide."
Source: eCFR: 40 CFR 503.40, Applicability (as of Nov 4, 2026)
19. Under 503.45(e), the operating combustion temperature of a sewage sludge incinerator may not exceed which temperature by more than 20 percent?
- A. The performance test combustion temperature
- B. The temperature at the stack exit
- C. The ambient air temperature
- D. The temperature of the auxiliary fuel
Show answer
Answer: A. The performance test combustion temperature
Operation "shall not cause the operating combustion temperature for the sewage sludge incinerator to exceed the performance test combustion temperature by more than 20 percent."
Source: eCFR: 40 CFR 503.45, Management practices (as of Nov 4, 2026)
20. Under 503.43(e)(3)(iii), how is the control efficiency for a pollutant determined from a performance test?
- A. The highest control efficiency of the three runs
- B. The arithmetic mean of the control efficiencies from the three runs
- C. The lowest control efficiency of the three runs
- D. The control efficiency of a single run at the lowest feed rate
Show answer
Answer: B. The arithmetic mean of the control efficiencies from the three runs
"Each performance test shall consist of three separate runs using the applicable test method. The control efficiency for a pollutant shall be the arithmetic mean of the control efficiencies for the pollutant from the three runs."
Source: eCFR: 40 CFR 503.43, Pollutant limits (as of Nov 4, 2026)