ENCE411 Exam 2

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ENCE411 Exam 2
2012-11-20 09:30:53

exam 2 flashcards
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  1. _____________ is an effective method for removal of volatile organic compounds (VOC's).
  2. What are some important examples of gas transfer in water ttmt?
    • 1) oxygen transfer to biological processes
    • 2) Stripping of VOC's
    • 3) CO2 exchanges as it relates to pH control
    • 4) Ammonia removal by stripping
    • 5) Odor removal - volatile sulfur compounds 
    • 6) Chlorination, ozonation, for disinfection or odor control
  3. What is occuring to the gas molecules when a jar of liquid is in equilibrium?
    The number of molecules leaving the liquid is equal to the number of molecules entering the liquid.
  4. What is the definition of solubility?
    The concentration of gas in water at equilbrium
  5. What is the definition of transfer rate?
    The rate of which dissolution or release occurs.
  6. Why is dissolved oxygen important for monitoring water treatment? 
    • Too much DO can be lethal for aquatic life - "gas bubble disease"
    • Too little DO can prevent respiration, decomposition, and various chemical reactions.
  7. The concentration of dissolved oxygen is higher/lower in the colder winter months of December through February, and higher/lower during the summer months of June through September. 
    • Higher...Lower
    • The solubility of oxygen in water is much higher in lower temperatures. When the water is colder, there is less energy for the water and oxygen molecules to move, and the oxygen remains trapped in the water
  8. kLa increases/decreases as airflow increases. Explain
    • Increases
    • The Kla value reflects the rate at which the water is uptaking O2.
  9. What is added to the water to deoxygenate it? Why do we do this?
    • CoCl2 and Na2SO3
    • So that we can test the reuptake rate of oxygen in the form of DO 
  10. What is the procedure for finding kLa? 
    • 1) Deoxygenate water with stuff 
    • 2) Start Test (turn on aeration device)
    • 3) monitor DO
    • 4) Plot Cs-Ct over time on semi log graph
    • 5) Slope = kLa
  11. Adsorption
    the process by which a substance (adsorbate) is collected onto the surface of an adsorbent to remove it from a water stream/the process by which “a surface” removes substances from water
  12. Why is adsorption important in Water treatment?
    Adsorption of contaminants in water onto activated carbon is often used for purification of water. Sorption processes are also important for the fate and transport of contaminants in the environment.
  13. Activated Carbon uses the physical adsorption process whereby attractive ______________ forces  pull the solute out of solution andonto its surface.
    van der Waals 
  14. What is qe in terms of adsorption?
    • qe = mass of material adsorbed (at equilibrium) per mass of adsorbent
    • ex. mass of pollutant adsorbed per total mass of coal  
  15. ___________ are empirical relations which are used to predict how much solute can beadsorbed by activated carbon.
  16. In adsorption, Kd=?
    Kd = Volume of Solution/Mass Solid
  17. On log-log isotherm plots, more adsorbable chemicals have ______ and _____ lines than less adsorbable chemicals.
    higher, flatter
  18. Show neutralization of hydrochloric acid solution (HCl) with the base sodium hydroxide (NaOH)
    HCl(aq)  +  NaOH(aq)   à  H2O(l) + NaCl(aq)
  19. Factors that affect pH in water
    • Algal blooms• Bacterial activity• Water turbulence• Chemicals flowing into the water body• Sewage overflows• Pollution
  20. ability to resist change in pH is called...
    buffering capacity
  21. How does increased pH aggravate problems in the water (not aquatic life, but plants)
    achange in pH may increase the solubility ofphosphorus, making it more available for plant growthand resulting in a greater long-term demand fordissolved oxygen.
  22. what is the definition of alkalinity of water?
    a measure of its capacity to neutralize acids and resist change to pH
  23. Significance of alkalinity in water ttmt?
    Chemical coagulation, water softening, corrosion control, acid rain precipitation