B test material - TCEQ Class B Surface Water Questions and Correct Answers the Latest Update and Recommended Version
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Course
TCEQ
Institution
TCEQ
What is the most important factor affecting the useful life of service lines?
It is the ability of the material to resist internal and external corrosion
When does Suction Head exist?
Suction head exists when the source of supply is above the centerline of the pump.
What is Net positive Sucti...
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B test material - TCEQ Class B Surface
Water Questions and Correct Answers
the Latest Update and Recommended
Version
What is the most important factor affecting the useful life of service lines?
✓ It is the ability of the material to resist internal and external corrosion
When does Suction Head exist?
✓ Suction head exists when the source of supply is above the centerline of the pump.
What is Net positive Suction Head (NPSH)
✓ NPSH is the pressure under which water enters the eye of the impeller in a centrifugal
pump. Insufficient NPSH is the main cause of pump cavitation
Explain and expand on Chlorine Dioxide (what it reacts with, oxidizes, etc)
✓ Chlorine Dioxide is a gas used in small quantities to disinfect water. It does not react with
organics to form THMs and HAAs. It oxidizes phenols, manganese, iron, sulfurous and
organic compounds which aids in the removal of tastes and odors. It is a very effective
bactericide and a superior virocide. It dies not combine with ammonia. Chlorine Dioxide
MRDL is .8 mg/L and monitoring procedures are the same as for chlorine. The Chlorite
MCL is .q mg/L and must be monitored daily.
What is texas drinking water pH requirements?
✓ The texas drinking water requirements require a pH > 7.0 for the water treatment plant
finished water. EPA requires that pH analysis be preformed within 15 minutes of the
sample being caught.
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✓ When chlorine is added to water it forms hypochlorous acid (HOCL) and hydrochloric
acid (OCL). The hypochlorous acid is the effective disinfectant. At a pH of 4.0 there is
100% hypochlorous acid. At a pH of 11 there is 100% hypochlorite ion. At a pH of 7,
the hypochlorous acid is at about 80% and the hypochlorite ion makes up about 20% of
the chlorine content. The lower the pH is more effective chlorine is because you have more
hypochlorous acid.
What is meant by water stability?
✓ Stable water is defined as water that will neither deposit or dissolve a calcium carbonate
film or scale. Since no water is stable indefinitely, chemical treatment of water usually is
intended to produce water that is slightly scale forming without being liable to cause
stoppages in small lines and services. Bayliss curve is the simplest determination of
stability. The Langelier saturation index is also used.
What/how are above ground tanks and piping protected from corrosion?
✓ Corrosion protection for above ground tanks and piping is prevented by: cathodic
protection, use if protective linings/coatings, eliminating different types of metals in the
distribution system, and treating the water with chemicals to make it less corrosive
How do you tests fir alkalinity?
✓ The two tritiation methods of analysis are a standard acid to titrate a sample. The end
point of the titration is determined by the following: an indicator that changes color at a
certain pH, or potentiometric titration to end - point pH. Using either of the methods, a
measured amount of sample is titrated with a standard sulfuric acid to a predetermined
pH. Nomograph are a graphical form of determining alkalinity. If the pH, total alkalinity,
temperature and total dissolved solids are known, any or all of the alkalinity forms may
be estimated.
What is Turbidity?
✓ Turbidity can be described as a measure of the relative clarity of water. Turbidity is an
expression of the optical property that causes light to be scattered and absorbed rather
than transmitted in straight lines through the sample.
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✓ Turbidity is caused by clay, slit, finely divided organic and inorganic material. Other
suspended matter and microscopic organisms can also cause turbidity. There is one
approved method for running turbidity - the Nephelometric Method (NTU)
What is chlorine Demand?
✓ The amount of chlorine used up to completely react with the water and its suspended or
dissolve material
What is chlorine residual?
✓ When all the demand of the water is met any additional chlorine produces a chlorine
residual
What is chlorine dosage?
✓ Demand plus residual is the chlorine dosage. Chlorine Dosage = Demand + Residual
What determines rate of disinfection?
✓ Chlorine concentration and contact time determines the rate and degree of disinfection. If
concentration increases, the time can be reduced; if concentration is reduced the time must
be increased.
How does temperature effect chlorine effectiveness?
✓ Chlorine effectiveness is greater at higher temperatures, up to the point that chlorine
volatizes. At low temperature, chlorine is more stable, but disinfection time increases.
Is removing turbidity important for disinfection?
✓ Turbidity must be removed to low levels by sedimentation and filtration to allow chlorine
to contact pathogens.
What happens to dissolved solids on contact with chlorine?
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✓ Dissolved solids are oxidized on contact further reinforcing the importance of contact
time.
No residual is formed until reducing agents are destroyed. What are examples of reducing
agents?
✓ Manganese, iron, turbidity, organic matter, ammonia, or nitrates
What the 4 stages of the Chlorine Demand Curve chart?
✓ Stage 1: No residual is formed because inorganic demand destroys the chlorine. (Flat
Line)
✓
✓ Stage 2: Monochloramines are formed as chlorine combines with organics containing
ammonia (rising curve). The chlorine to ammonia weight ratio at this point is 5:1.
Combined and total residual increases, chloro-organics are formed.
✓
✓ Stage 3: Increasing chlorine dosage (failing curve) to a chlorine/ammonia weight ratio
of 7.6:1 destroys chloramines and chloro-organics. Combined decreases and free chlorine
increases.
✓
✓ Stage 4: Enough chlorine is added to reduce all demand. The combined residual remains
the same, but free residual increases with dosage. This stage is called "breakpoint"
chlorination. The chlorine to ammonia ratio of 10:1 satisfies all demand and disinfects the
distribution system. ( second rising curve)
What is the difference between free chlorine and combined chlorine (chloramines/chlorine-
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