WTO Source Water Characteristics 2 — Questions and Answers
Question 1: Which parameter best indicates the presence of fecal contamination in a surface water source?
- Total dissolved solids
- Fecal coliform count (Correct answer)
- Water hardness
- Alkalinity level
Correct answer: Fecal coliform count
Fecal coliform bacteria, particularly E. coli, are the primary indicators of fecal contamination in source water.
Question 2: What is the primary cause of seasonal taste and odor problems in reservoir source water?
- High iron concentration
- Algal blooms producing geosmin and MIB (Correct answer)
- Chlorine residual decay
- Excessive sedimentation
Correct answer: Algal blooms producing geosmin and MIB
Algae produce geosmin and 2-methylisoborneol (MIB) as metabolic byproducts, causing earthy or musty taste and odor complaints.
Question 3: A source water with a pH of 9.5 is best described as:
- Strongly acidic
- Slightly acidic
- Neutral
- Strongly alkaline (Correct answer)
Correct answer: Strongly alkaline
A pH of 9.5 is well above the neutral point of 7.0, placing it firmly in the alkaline (basic) range.
Question 4: What does a high total organic carbon (TOC) level in source water indicate to a water treatment operator?
- Low risk of disinfection byproduct formation
- Greater potential for DBP formation during chlorination (Correct answer)
- Reduced coagulant demand
- Better aesthetic water quality
Correct answer: Greater potential for DBP formation during chlorination
High TOC provides more precursor material that reacts with chlorine to form disinfection byproducts such as trihalomethanes and haloacetic acids.
Question 5: Which source water type is most susceptible to rapid quality changes following a heavy rainfall event?
- Deep confined aquifer
- Unconfined artesian well
- Surface water reservoir (Correct answer)
- Naturally filtered spring
Correct answer: Surface water reservoir
Surface water reservoirs are directly exposed to watershed runoff, causing rapid increases in turbidity, pathogens, and contaminants after rain events.
Question 6: The ratio of bicarbonate, carbonate, and hydroxide ions in source water determines its:
- Hardness
- Turbidity
- Alkalinity (Correct answer)
- Conductivity
Correct answer: Alkalinity
Alkalinity is defined by the buffering capacity of water, primarily contributed by bicarbonate, carbonate, and hydroxide ions.
Question 7: Which natural process is primarily responsible for elevated iron and manganese concentrations in groundwater sources?
- Photosynthesis by aquatic plants
- Dissolution from geological formations under anaerobic conditions (Correct answer)
- Surface runoff from agricultural areas
- Atmospheric deposition
Correct answer: Dissolution from geological formations under anaerobic conditions
Iron and manganese dissolve from mineral-bearing geological formations when oxygen is depleted in groundwater, creating reducing (anaerobic) conditions.
WTO Source Water Characteristics 2
Which parameter best indicates the presence of fecal contamination in a surface water source?