ETC Water Quality & Treatment 2 — Questions and Answers
Question 1: What is the regulatory significance of Total Maximum Daily Load (TMDL) under the Clean Water Act?
- It sets the maximum amount of a pollutant a water body can receive and still meet water quality standards (Correct answer)
- It establishes the maximum daily discharge from a single industrial facility
- It defines the total amount of water that can be withdrawn from a surface water body
- It limits the total loading of groundwater contaminants in an aquifer system
Correct answer: It sets the maximum amount of a pollutant a water body can receive and still meet water quality standards
A TMDL is a calculation of the maximum daily pollutant load a water body can receive from all sources while still attaining its water quality standards, serving as the basis for allocating loads among point and nonpoint sources.
Question 2: Which treatment technology uses semi-permeable membranes under pressure to remove dissolved salts and contaminants from water?
- Ultrafiltration
- Reverse Osmosis (RO) (Correct answer)
- Nanofiltration
- Activated Carbon Filtration
Correct answer: Reverse Osmosis (RO)
Reverse osmosis forces water through semi-permeable membranes under high pressure, rejecting dissolved salts, heavy metals, nitrates, and other contaminants while allowing water molecules to pass through.
Question 3: What is the primary mechanism by which activated carbon (GAC) removes contaminants from drinking water or groundwater treatment systems?
- Ion exchange replacing target ions with harmless counterions
- Physical adsorption of organic molecules and some inorganics onto the carbon surface (Correct answer)
- Biological degradation of contaminants on the carbon surface
- Chemical oxidation of pollutants catalyzed by the carbon matrix
Correct answer: Physical adsorption of organic molecules and some inorganics onto the carbon surface
Granular activated carbon (GAC) removes contaminants primarily through physical adsorption, where organic molecules and some inorganic compounds are attracted to and held on the highly porous carbon surface.
Question 4: Eutrophication of a lake or reservoir is primarily caused by excess loading of which two nutrients from agricultural and urban runoff?
- Calcium and magnesium
- Iron and manganese
- Nitrogen and phosphorus (Correct answer)
- Potassium and sulfur
Correct answer: Nitrogen and phosphorus
Excess nitrogen and phosphorus stimulate explosive algal growth (algal blooms) that depletes oxygen when the algae die and decompose, causing eutrophication that harms aquatic life and impairs water uses.
Question 5: What is the regulatory trigger for a Tier 1 public notification under the Safe Drinking Water Act?
- A routine monitoring violation for a secondary contaminant
- An acute health risk violation such as a positive E. coli result or MCL exceedance for nitrate (Correct answer)
- Missing a quarterly sampling event for lead and copper
- Exceeding an aesthetic water quality standard for color or odor
Correct answer: An acute health risk violation such as a positive E. coli result or MCL exceedance for nitrate
Tier 1 (24-hour) notification is required when violations or situations pose an acute risk to public health, such as a positive total coliform/E. coli result, nitrate MCL exceedance, or system going off-line without backup.
Question 6: A stormwater technician observes turbid runoff from a construction site entering a storm drain. Which regulatory program is the construction site most likely violating?
- RCRA Subtitle D solid waste management requirements
- NPDES Construction General Permit (CGP) stormwater requirements (Correct answer)
- Clean Air Act fugitive dust emission standards
- SDWA source water protection program requirements
Correct answer: NPDES Construction General Permit (CGP) stormwater requirements
Construction sites disturbing one or more acres must obtain coverage under the NPDES Construction General Permit, which requires implementation of BMPs (sediment traps, silt fence) to prevent turbid stormwater discharge.
