HIC Sewage & Waste Disposal Systems 3 — Questions and Answers
Question 1: An inspector observes sewage surfacing in a yard above a drain field after heavy rainfall. The MOST likely cause is:
- Oversized septic tank
- Hydraulic overloading of saturated soil (Correct answer)
- Insufficient inlet baffle depth
- Improper tank lid seal
Correct answer: Hydraulic overloading of saturated soil
Heavy rainfall saturates the soil in the drain field, preventing effluent absorption, which causes hydraulic overloading and sewage surfacing.
Question 2: What is the purpose of a 'dosing' or 'pump' chamber in an advanced septic system?
- To add disinfectant chemicals to the effluent
- To deliver measured doses of effluent to the drain field at timed intervals (Correct answer)
- To pump raw sewage to an elevated tank
- To recirculate effluent back to the primary tank
Correct answer: To deliver measured doses of effluent to the drain field at timed intervals
A dosing chamber uses a pump to deliver timed, measured doses of effluent to the drain field, promoting more uniform distribution and resting periods for soil recovery.
Question 3: BOD (Biochemical Oxygen Demand) is a measure of:
- The amount of dissolved oxygen in treated water
- The oxygen required by microorganisms to decompose organic matter in wastewater (Correct answer)
- The concentration of bacteria per milliliter of effluent
- The turbidity of wastewater before treatment
Correct answer: The oxygen required by microorganisms to decompose organic matter in wastewater
BOD measures the amount of oxygen microorganisms need to break down organic material in wastewater; higher BOD indicates greater organic pollution.
Question 4: A health inspector finds a cesspool at a food service establishment. The correct action is to:
- Allow it if it is being pumped regularly
- Require immediate connection to an approved sewer or septic system (Correct answer)
- Issue a warning and re-inspect in 90 days
- Approve it if no odors are detected at the property line
Correct answer: Require immediate connection to an approved sewer or septic system
Cesspools are prohibited for food service establishments in most jurisdictions and must be replaced with an approved sewage disposal system due to serious public health risks.
Question 5: What is the required minimum slope for building sewer pipes to ensure proper flow by gravity?
- 1/16 inch per foot
- 1/8 inch per foot (approximately 1%)
- 1/4 inch per foot (approximately 2%) (Correct answer)
- 1/2 inch per foot
Correct answer: 1/4 inch per foot (approximately 2%)
Building sewers typically require a minimum slope of 1/4 inch per foot (about 2%) to maintain a self-cleaning velocity of approximately 2 feet per second.
Question 6: Which type of soil is LEAST suitable for a conventional drain field?
- Sandy loam
- Silty clay (Correct answer)
- Well-graded gravel
- Loamy sand
Correct answer: Silty clay
Silty clay has very slow percolation rates and poor drainage characteristics, making it unsuitable for conventional drain fields without significant soil modification or an alternative system.
Question 7: Under the Clean Water Act, what document authorizes a facility to discharge treated wastewater into a water body?
- A Variance Permit
- An NPDES Permit (Correct answer)
- A 404 Dredge-and-Fill Permit
- A State Operating License
Correct answer: An NPDES Permit
The National Pollutant Discharge Elimination System (NPDES) permit sets limits and conditions for discharging pollutants, including treated wastewater, into surface waters.
HIC Sewage & Waste Disposal Systems 3
An inspector observes sewage surfacing in a yard above a drain field after heavy rainfall.
The MOST likely cause is: