Mock Exam: Water Quality

1

Under the Clean Water Act's NPDES (National Pollutant Discharge Elimination System) program, the technology-based effluent limits progress from BPT to BAT for toxic pollutants. What do these acronyms stand for and how do they differ?

A. BPT = Best Practicable Technology (economically achievable for the industry); BAT = Best Available Technology Economically Achievable (stricter, requires state-of-the-art treatment)
B. BPT = Basic Pollution Treatment (minimum standards); BAT = Best Allowable Treatment (for permits only)
C. BPT = Best Prevention Technology (source reduction); BAT = Best Analytical Technology (for monitoring)
D. BPT = Baseline Performance Test; BAT = Baseline Achievable Technology

2

Which term describes the process by which a stream ecosystem gradually changes from a disturbed state to a complex biological community over time?

Aquatic Ecology & Food Webs intermediate

A. Eutrophication
B. Ecological succession
C. Biomagnification
D. Stratification

3

Methylmercury (MeHg) crosses the blood-brain barrier far more effectively than inorganic mercury (Hg²⁺). Which property of methylmercury best explains this difference?

A. Methylmercury has a higher molecular weight than inorganic mercury salts
B. Methylmercury is lipophilic and can passively diffuse across lipid bilayers, while inorganic Hg²⁺ is ionic and cannot
C. Methylmercury binds to albumin, which is actively transported across the blood-brain barrier
D. Inorganic mercury is rapidly excreted by the kidneys before it can reach the brain

4

Looking at the dragonfly nymph image, what is the most distinctive feature that separates it from a damselfly nymph?

macroinvertebrates medium

5

Spring turnover in a lake typically occurs because:

Thermal Stratification intermediate

A. Spring rains increase nutrient inputs, causing a mixing event
B. Ice melts and surface water warms to 4°C (maximum density), sinks, and homogenizes the water column
C. Increasing solar radiation heats the hypolimnion first
D. Fish spawning migrations create sufficient turbulence to mix the lake

6

Explain the concept of 'mitigation banking' under Section 404 of the Clean Water Act and describe why regulatory agencies prefer it over permittee-responsible mitigation.

7

Inside the septic tank, what happens to the solids in the wastewater?

Septic systems — function and failure beginner

A. They are chemically neutralized by added lime and dissolved into the effluent
B. They settle to the bottom as sludge, float as scum, and anaerobic bacteria digest the organic solids, reducing their volume
C. They are filtered through a screen before the clarified effluent flows to the drain field
D. They are pumped out continuously to prevent buildup in the tank

8

The life stage of a macroinvertebrate used in bioassessment is typically:

Macroinvertebrates beginner

A. Only adult flying insects collected from streamside vegetation
B. The larval or nymph stage living in the stream substrate
C. Egg masses attached to rocks in the streambed
D. The pupal stage emerging at the water surface

9

Below pH 5.5, fish experience 'osmoregulatory failure.' What does this specifically mean?

Effects of pH on aquatic life intermediate

A. Fish cannot produce enough mucus to protect their scales from acidic water
B. Fish lose the ability to regulate ions (Na⁺, Cl⁻, Ca²⁺) across their gills, causing ions to leak out of their blood
C. Fish metabolic rates slow so drastically that they cannot take up adequate oxygen
D. Fish swim bladders fail to regulate buoyancy in acidic water, causing them to sink

10

On the pH scale, each unit change represents a ___-fold change in hydrogen ion concentration.

pH & Acid/Base Chemistry beginner

A. 2-fold
B. 5-fold
C. 10-fold
D. 100-fold

11

According to the energy pyramid concept described in SOINC materials, approximately what percentage of energy passes from one trophic level to the next?

food_webs easy

A. About 10%, with ~90% lost as heat and respiration
B. About 50%, with ~50% lost
C. About 90%, with ~10% lost
D. About 25%, with ~75% lost

12

Which chemical reaction correctly represents the formation of carbonic acid in water (contributing to natural water acidity)?

pH & Acid/Base Chemistry intermediate

A. CO₂ + H₂O → H₂CO₃
B. H₂ + O₂ → H₂O₂
C. CaCO₃ + H₂O → Ca(OH)₂ + CO₂
D. NaCl → Na⁺ + Cl⁻

13

During winter in a temperate lake with ice cover, which layer of water is densest?

Thermal Stratification intermediate

A. The surface water just under the ice (~0°C)
B. Water at mid-depth (~2°C)
C. Water at the bottom (~4°C)
D. Water is equally dense throughout under ice

14

A stream has a measured DO of 7.2 mg/L. At the current water temperature, the DO saturation value (100% saturated) is 9.0 mg/L. What is the percent saturation of dissolved oxygen?

DO % Saturation medium

A. 72%
B. 78%
C. 80%
D. 75%

15

What does EPT stand for in the context of bioassessment?

EPT richness and EPT index beginner

A. Ephemeroptera, Plecoptera, Trichoptera
B. Ephemeroptera, Pisces, Tubificida
C. Ecological Pollution Tolerance
D. Emergent, Periphyton, Turbidity

16

What do we call the accumulation of heavy metals and pesticides in the food chain?

Biomagnification & Contaminants beginner

A. Biomagnification
B. Predation
C. Biogenesis
D. Necrosis

17

Which of the following statements about potable water treatment is correct?

Water Treatment intermediate

A. Over 95% of the world population had access to improved drinking water in 2015
B. Coagulation is not needed in modern treatment plants
C. Flocculation is not needed if coagulants are used
D. Clarification (sedimentation) is a necessary step in potable water treatment

18

In what way are oligotrophic and eutrophic lakes different according to SOINC classification?

thermal_stratification easy

A. Oligotrophic = clear water, low productivity, high oxygen; Eutrophic = very productive, may experience oxygen depletion, rough fish common
B. Oligotrophic = warm, nutrient-rich, algae blooms; Eutrophic = cold, deep, nutrient-poor
C. Oligotrophic = shallow and murky; Eutrophic = deep and clear
D. Oligotrophic = salt water; Eutrophic = freshwater

19

In biological nitrogen removal, denitrification permanently removes nitrogen from wastewater. What is the end product released to the atmosphere?

Nutrient removal in wastewater (N and P) beginner

A. Ammonia (NH₃)
B. Nitrous oxide (N₂O)
C. Nitrogen gas (N₂)
D. Nitrogen dioxide (NO₂)

20

The pH scale is logarithmic, which means that each whole-unit change in pH represents:

pH scale and measurement beginner

A. An additive change of 1 unit in hydrogen ion concentration
B. A 10-fold change in hydrogen ion concentration
C. A 100-fold change in hydrogen ion concentration
D. A change proportional to temperature in degrees Celsius

21

What distinguishes 'autogenic' from 'allogenic' drivers of aquatic succession?

Succession in aquatic systems intermediate

A. Autogenic drivers are human-caused; allogenic drivers are natural
B. Autogenic factors are changes caused by the organisms themselves; allogenic factors are external drivers like watershed erosion and nutrient loading
C. Autogenic succession occurs in streams; allogenic succession occurs in lakes
D. Autogenic drivers speed succession; allogenic drivers slow it

22

What does 'no net loss' mean as a wetlands policy goal?

§404 — wetlands dredge-and-fill permits intermediate

A. No wetland may be filled under any circumstances without a federal criminal investigation
B. Total U.S. wetland area and function should not decline — losses through permitted fills must be compensated by equivalent gains through mitigation
C. EPA must approve every wetland permit application before USACE can issue it
D. States must demonstrate a net increase in wetland acreage every five years

23

According to the EPA Macroinvertebrate Factsheet, which of the following correctly lists organisms from most pollution-INTOLERANT to most pollution-TOLERANT?

macroinvertebrates medium

A. Stonefly (intolerant) → Mayfly (intolerant) → Crayfish (moderately tolerant) → Leech (tolerant) → Aquatic worm (tolerant)
B. Aquatic worm (intolerant) → Leech (intolerant) → Crayfish (moderately tolerant) → Mayfly (tolerant) → Stonefly (tolerant)
C. Leech (intolerant) → Crayfish (moderately tolerant) → Stonefly (tolerant) → Mayfly (moderately tolerant)
D. All macroinvertebrates have the same pollution tolerance

24

The EPA Maximum Contaminant Level (MCL) for arsenic in drinking water is 0.010 mg/L. Express this concentration in µg/L and ppb.

Unit Conversions medium

A. 0.010 µg/L = 0.010 ppb
B. 10 µg/L = 10 ppb
C. 100 µg/L = 100 ppb
D. 0.001 µg/L = 0.001 ppb

25

In an MPN test using three dilutions (10 mL, 1 mL, 0.1 mL), why are more tubes expected to be positive at the 10 mL volume than at the 0.1 mL volume?

MPN Method beginner

A. The selective medium is more concentrated in the 10 mL tubes
B. At the lowest dilution (largest volume), each tube receives many bacteria, virtually guaranteeing growth
C. Gas production takes longer at higher dilutions
D. The 10 mL volume incubates at a higher temperature

26

For the WQI temperature parameter, what scenario would result in a score near zero (worst possible)?

Water Quality Index (WQI) advanced

A. Water temperature equals upstream ambient temperature
B. Water temperature is 1°C above ambient
C. Water temperature is 15°C or more above ambient (severe thermal pollution)
D. Water temperature is below ambient due to snowmelt

27

A 'non-monotonic dose-response curve' in the context of endocrine-disrupting compounds means:

Endocrine-disrupting compounds (basics) intermediate

A. Higher doses always produce proportionally stronger toxic effects
B. The dose-response relationship follows a simple linear pattern from zero to maximum effect
C. EDCs can trigger larger biological responses at very low doses than at intermediate doses, because hormone systems naturally operate at low concentrations and can be paradoxically disrupted more at low than high exposure
D. The dose-response relationship is completely unpredictable and varies randomly between individual organisms

28

Which two bacteria are responsible for the two-step nitrification process in biological nitrogen removal?

Nutrient removal in wastewater (N and P) beginner

A. Nitrosomonas (ammonia → nitrite) and Nitrobacter (nitrite → nitrate)
B. Nitrobacter (ammonia → nitrite) and Nitrosomonas (nitrite → nitrate)
C. Pseudomonas (ammonia → nitrate) and Bacillus (nitrate → nitrogen gas)
D. Acinetobacter (ammonia → nitrate) and Thiobacillus (nitrate → nitrogen gas)

29

Which of the following is an example of POINT SOURCE pollution?

Watershed & Pollution Sources beginner

A. Fertilizer runoff from thousands of farms throughout a region
B. Pesticide drift from crop-dusting operations
C. Discharge pipe from a factory releasing industrial wastewater
D. Atmospheric deposition of nitrogen from vehicle emissions

30

What is the technical term for the successional sequence from open water to terrestrial community in a filling lake or pond?

Succession in aquatic systems beginner

A. Xerosere
B. Lithosere
C. Hydrosere
D. Halosere

💧 Water Quality Mock Exam