WTO - Water Treatment Operator Source Water Characteristics Questions and Answers 1 — Questions and Answers
Question 1: A water treatment plant operator observes a sudden increase in turbidity in the raw water from a river source after a heavy rainfall. Which of the following is the MOST significant and immediate operational concern related to this change?
- A decrease in water temperature affecting chemical reaction rates.
- An increase in dissolved oxygen levels impacting aquatic life.
- A sudden drop in the pH of the source water.
- A reduced effectiveness of the disinfection process. (Correct answer)
Correct answer: A reduced effectiveness of the disinfection process.
High turbidity, caused by suspended particles like silt and organic matter, can shield pathogenic microorganisms from disinfectants like chlorine. This shielding effect reduces the effectiveness of disinfection, posing a significant public health risk. The particles can also exert a higher disinfectant demand, consuming the disinfectant before it can inactivate pathogens.
Question 2: Which of the following BEST describes the primary cause of 'hardness' in a source water supply?
- High concentrations of sodium and potassium.
- The presence of dissolved organic compounds.
- Dissolved mineral salts, primarily calcium and magnesium. (Correct answer)
- Low pH and high acidity.
Correct answer: Dissolved mineral salts, primarily calcium and magnesium.
Water hardness is primarily caused by the presence of dissolved divalent cations, with calcium (Ca2+) and magnesium (Mg2+) ions being the most common contributors. These minerals are typically dissolved as water percolates through deposits of limestone, chalk, or gypsum.
Question 3: A groundwater well is showing consistently high levels of iron and manganese. Which physical characteristics would an operator most likely observe in the water before treatment?
- A noticeable 'rotten egg' odor.
- Reddish-brown or black staining and a metallic taste. (Correct answer)
- High levels of suspended solids and cloudiness.
- A salty taste and high conductivity.
Correct answer: Reddish-brown or black staining and a metallic taste.
Iron (Fe) and manganese (Mn) are common groundwater contaminants. When oxidized, iron produces a reddish-brown color, while manganese produces a brownish-black color. Both can impart an undesirable metallic taste and cause staining of laundry and plumbing fixtures.
Question 4: What does a high alkalinity measurement in source water indicate about its chemical characteristics?
- The water is highly acidic and corrosive.
- The water has a low concentration of dissolved minerals.
- The water has a high capacity to neutralize acids.
- The water is likely to be very soft. (Correct answer)
Correct answer: The water is likely to be very soft.
Alkalinity is a measure of water's capacity to neutralize acids, or its buffering capacity. It is primarily caused by the presence of carbonate, bicarbonate, and hydroxide ions. High alkalinity means the water can resist changes in pH when an acid is added.
Question 5: A water utility is using a surface water reservoir as its source. Which of the following biological contaminants are of greatest concern for requiring filtration and disinfection treatment, especially in surface water?
- Iron bacteria and sulfur-reducing bacteria.
- Algae and aquatic plants.
- Viruses and protozoa like Giardia and Cryptosporidium. (Correct answer)
- Total dissolved solids (TDS).
Correct answer: Viruses and protozoa like Giardia and Cryptosporidium.
Surface water sources are open to the atmosphere and runoff, making them susceptible to contamination from human and animal waste. Pathogenic microorganisms, including viruses and chlorine-resistant protozoa like Giardia and Cryptosporidium, are a major health concern and a primary target for filtration and disinfection processes in surface water treatment.
Question 6: An operator at a plant using river water notices an increase in musty and earthy tastes and odors. Which source water characteristic is the most likely cause?
- Increased water hardness.
- A drop in water temperature.
- An algal bloom. (Correct answer)
- High levels of iron.
Correct answer: An algal bloom.
Certain species of algae and cyanobacteria produce organic compounds, such as geosmin and 2-Methylisoborneol (MIB), which cause distinct earthy and musty tastes and odors, even at very low concentrations. These events, known as algal blooms, are common in surface water sources.
WTO - Water Treatment Operator Source Water Characteristics Questions and Answers 1
A water treatment plant operator observes a sudden increase in turbidity in the raw water from a river source after a heavy rainfall.
Which of the following is the MOST significant and immediate operational concern related to this change?