CEE 561 - Physical-Chemical Treatment of Water and Wastes
Homework #2 (due February 8, 2020)
For each problem, write the complete question and then immediately below your solution. Highlight the answer.
Show ALL steps. Do not hand in the same solution as a classmate – you may collaborate in working through
problems, but then write up your own solutions.
Part I – Discussion Board Chat on CANVAS (see instructions in CANVAS)
1. Follow instructions for “Tracer Studies Discussion Posts) – 10 points
Part II – Answer only graded problems. Only the final answer is graded as correct or non-correct for full credit
2. Problem 4-7 Part A from Howe et al. ( 10 points)
3. Problem 4-8 part A from Howe et al. ( 10 points)
4. Problem 4-9 for part A from Howe et al.; Write 1-2 complete sentences that compare this answer with
Problem 4-8 Part A. ( 10 points)
5. Problem 4-10 part A from Howe et al. ( 10 points)
6. Problem 4-11 from Howe et al. ( 10 points)
Part III – Fully graded problems. Partial credit awarded based upon effort, completeness, obtaining correct
answers and using correct notation, including on significant figures (use 2 significant figures throughout).
7. Using data from Problem 4-12 Reactor D from Howe et al.. Plot the tracer concentration versus time
curve. Determine the following (35 points):
a. Determine and plot the E curve
b. Determine and plot the F curve
c. Determine the hydraulic residence time ()
d. Determine the mean residence time ( 𝑡̅ )
e. Variance of the residence time distributions
f. Mass and percentage of the dye recovered
g. Ratio of t10 / 
h. Equivalent number of CSTRs in series
i. Dispersion number (D/UL)
j. Why or when would you conduct a declining tracer test? Give 2-3 examples.
8. Geosmin is taste and odor compound that can be oxidized during ozonation based upon the following
reactions (15 points):
Geosmin + O3 = Product1
k = 1.0 M-1s-1
Geosmin + HO = Product2
k = 5.0 x109 M-1s-1
Geosmin oxidized by molecular ozone (O3) and hydroxyl radicals (HO). During ozonation the steadystate ratio of HO/O3 (Rct) equals 3x10-8 mole/mole.
a. Write the rate law for Geosmin degradation
b. Given the two reactions below, use kinetic rate analysis to determine the relative percentage of
Geosmin oxidized by molecular ozone (O3) and hydroxyl radicals (HO).
c. Write 1-2 complete sentences describing HO radicals are produced during ozonation.