Question

1).         A plug-flow reactor has a flow pattern of uniform velocity and concentration in the axial (longitudinal) direction.

(T), (F)

2).         For natural water (pH around 6−8), alkalinity is equal to the concentration of HCO₃^-. (T), (F)

3).         Unit operation means a treatment unit in which “treatment” is accomplished through chemical/biological means.  (T), (F)

4).        Based on the law of mass action, the reaction rate is proportional to the remaining concentration of the products

(T), (F)

5).        Strict household use from public water supply systems is about 105 gpd for each person served.  (T), (F)

6).        It is generally reported that about 60%−80% of the total water supplied to a community becomes wastewater. (T), (F)

7).        For n-CSTRs in series, when n  , the response of these n-CSTRs for a tracer input is the same as a plug-flow reactor. (T), (F) (Note: if you don’t know this, study my notes a bit and then do it)

8).        In flocculation tank design, the GT value of the floculation tank should be around 50000-100000. (T), (F)

9).        Zeta potential is the magnitude of the charge at the surface of shear. (T), (F)

10).       To design a flocculation tank with 4 compartments, the G value in each compartment should be reduced from about 70 to 10 s^-1. (T), (F)

11).       The performance of a plug-flow reactor is as like as a batch reactor that have a reaction time to be exactly the same as the hydraulic retention time of the plug-flow reactor.  (T), (F)

12).       Hardness in water is caused by the ions of calcium, magnesium, HCO₃^-, and CO₃^2-. (T), (F)

13).       After excess-lime treatment, the water is scale forming and must be neutralized to remove caustic alkalinity.  The chemical process to accomplish this task is called recarbonation.  (T), (F)

14).       According to minimum national standards for secondary treatment, the average 30-day concentrations of BOD₅ and SS should be less than 30 mg/L.  (T), (F)

15).       The design year is the year when the facilities reach their full designed capacity.  (T), (F)

16).       The design flow rate is usually assumed to be the average daily flow rate at the beginning of the design period.  (T), (F)

17).       For type I sedimentation, if the Re number is < 2000, the flow is a laminar flow. (T), (F)

18).       In U.S drinking water regulations, the second type of regulation specifies treatment technology in lieu of MCLs when it is infeasible to determine the level of a contaminant in drinking water.  (T), (F)

19).       Three types of sewer systems are used for the removal of wastewater and stormwater: sanitary sewer system, storm sewer systems, and combined sewer systems.  (T), (F)

20).       To design a sand filter, the two most important parameters about the filter media are P₁₀, and P₅₀. (T), (F)

Answer 1