Water Characteristics
What is the term used to describe bacteria, viruses or other organisms capable of causing disease?
A. Pathogenic, B. Non-Pathogenic, C. Coliform, D. Facultative
A. Pathogenic
What is the primary purpose of coagulation in water treatment?
A. Remove dissolved gases
B. Lower the pH of the water
C. Neutralize particle charges for aggregation
D. Kill bacteria and viruses
C — Coagulation neutralizes electrical charges on particles so they can aggregate.
Which disinfectant will effectively kill giardia, crypto, protozoans, and some viruses?
A. Chlorine, B. Monochloramines, C. Dichloramines, D. Chlorine Dioxide
D. Chlorine Dioxide
In a direct filtration plant, coagulation must be precisely controlled because:
A. There is no flocculation stage to support particle growth
B. Settling basins remove all larger particles
C. It directly influences filter run times and turbidity performance
D. Chemical residuals must be minimized for downstream RO systems
C — In direct filtration, coagulation directly impacts filter performance since there's no sedimentation.
What is the disinfection byproduct formed by the use of Ozone?
A. Bromate
B. Chlorite
C. THMs
D. HAAs
A. Bromate
Algal blooms may create several problems such as taste and odors, depletion of oxygen in source water, shortened filter runs, and organic loadings. What is another problem associated with them?
A. Increased pH, B. Decreased diatoms, C. Reduced THM formations, D. Aerobic Conditions
A. Increased pH
Which condition favors the formation of strong, settleable floc?
A. High-intensity turbulence throughout the basin
B. Uniform, gentle mixing during flocculation
C. Low water temperature with minimal mixing
D. Rapid chemical addition without mixing
B — Gentle, consistent mixing allows floc to grow without breaking apart.
What is one disadvantage of using chloramines as a disinfectant?
A. Reduces formation of THMS
B. Reduces T&O
C. Weaker disinfectant than free chlorine
D. Increases T&O
C. Weaker disinfectant than free chlorine
Which of the following operational indicators suggests that filter ripening is needed after backwashing?
A. Immediate turbidity spike at filter startup
B. High chlorine residual at filter effluent
C. Pressure drop in the backwash line
D. pH decrease during filter run
A — Filter ripening occurs when effluent turbidity is temporarily high after a backwash; this can be managed by filter-to-waste or slow start.
How can gas ammonia leaks be detected?
A. Hydrochloric acid soaked rag on a stick
B. Citric acid vapors
C. Nitric acid soaked rag on a stick
D. Sulfuric acid vapors
A. Hydrochloric acid soaked rag on a stick
What is the main reason a water plant will try to maintain turbidity readings from .05 to .3 NTUs?
A. To reduce the load on the filters, B. To avoid consumer complaints, C. High turbidity will shield bacteria and pathogenic organisms from disinfection, D. To avoid solids build up in distribution system
C. High turbidity will shield bacteria and pathogenic organisms from disinfection
What is the effect of overdosing alum during the coagulation process?
A. Increases pH and improves settling
B. Causes re-stabilization of particles and poor floc formation
C. Enhances chlorine demand only
D. Reduces turbidity removal efficiency but improves disinfection
B — Overdosing can lead to charge reversal and restabilization of particles, worsening turbidity.
Which of the following would increase chlorine demand in raw water?
A. High alkalinity
B. Low pH
C. High TOC and ammonia levels
D. High dissolved oxygen
C — TOC and ammonia consume chlorine through oxidation and breakpoint reactions.
What is the most appropriate corrective action if a filter experiences early turbidity breakthrough?
A. Lower the coagulant dose
B. Increase backwash duration and inspect media for loss or fouling
C. Increase filtration rate
D. Add chlorine to the filter influent
B — Early breakthrough may indicate media problems or ineffective backwashing.
What type of corrosion occurs when two dissimilar metals are joined together?
A. Stray Current
B. Galvanic Corrosion
C. Immersion Corrosion
D. Dielectric Corrosion
B. Galvanic Corrosion
Which parameter is most likely to fluctuate daily in surface water sources?
A. Alkalinity
B. Nitrate
C. Temperature
D. Total dissolved solids (TDS)
C — Temperature can change quickly due to weather, especially in shallow reservoirs.
What is the chemical reaction that occurs when alum (Al₂(SO₄)₃·14H₂O) is added to water with sufficient alkalinity?
A. Formation of Al(OH)₃- Aluminum Hydroxide
B. Release of free chlorine
C. Formation of soluble aluminum sulfates
D. Formation of ferric hydroxide
A — Alum reacts with alkalinity (bicarbonate) to form insoluble Al(OH)₃, which is the active floc-forming species.
How does low pH improve the disinfecting properties of chlorine?
A. It doesnt
B. Low pH favors the hypochlorite ion, which is stable
C. Low pH levels form ozone as a byproduct
D. Hypochlorous acid is formed at lower pH levels
D. Hypochlorous acid is formed at lower pH levels
A plant is using dual-media filters (anthracite over sand). What is the primary advantage of this design over mono-media sand filters?
A. Requires less frequent backwashing
B. Promotes longer filter runs and better turbidity removal due to depth filtration
C. Operates without the need for coagulation
D. Eliminates the need for underdrains
B — Dual-media filters allow for better stratification, resulting in longer runs and deeper particle removal.
Why must alum sludge not be applied to agricultural land like lime sludge?
A. Alum sludge reduces the soil pH
B. Alum sludge hardens the soil
C. Alum Sludge adsorbs soil nutrients
D. Alum sludge can be used like lime sludge on agricultural land
B. Alum sludge hardens the soil
What is a key concern when using groundwater under the direct influence of surface water (GWUDI)?
A. Hardness variability
B. Presence of coliform bacteria
C. pH control
D. Elevated nitrate
B — GWUDI can contain pathogens like coliforms, so it's regulated similarly to surface water.
You observe increasing settled water turbidity despite stable raw water conditions and coagulant dose. The most likely cause is:
A. Increase in temperature
B. Ineffective flash mixing or floc breakup
C. Decrease in raw water TOC
D. Excessive hardness in raw water
B — Poor or too intense mixing can prevent proper floc formation or break floc apart.
A plant switches from free chlorine to chloramines for distribution system stability. What new risk must be closely monitored?
A. Bromate formation
B. Nitrification in the distribution system
C. Excessive TTHM formation
D. Scale formation in clearwells
B — Chloramines can degrade in the presence of nitrifying bacteria, leading to chlorine loss and nitrite/nitrate issues.
In membrane filtration (e.g., ultrafiltration), what is the most common operational issue that requires frequent monitoring and control?
A. pH increase
B. Organic acid buildup
C. Membrane fouling from organics and biofilm
D. Ammonia accumulation
C — Membrane fouling reduces flux and increases pressure; regular cleaning and pretreatment are critical.
Where should polyphosphates be added in relation to the introduction of chlorine?
A. Add polyphosphates before chlorine
B. Add polyphosphates after chlorine
C. Add polyphosphates with chlorine
D. There is no preferred point to add polyphosphates
A. Add polyphosphates before chlorine