Initial ______
CE 321 Introduction to Environmental Engineering
Exam II
November 17, 2004
7:00 - 9:00 pm
Room 315 AEC
Problem Solving
Problem 1 - 40 Points ______I______
Problem 2 - 10 Points ______I______Problem 3 - 10 Points ______I______
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Sub Total (60 Points) ______I______
Short Answers
S A #1 3 Points ______I______
S A #2 5 Points ______I______
S A #3 8 Points ______I______
S A #4 8 Points ______I______
S A #5 5 Points ______I______
S A #6 5 Points ______I______
S A #7 3 Points ______I______
S A #8 3 Points ______I______
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Sub Total (40 Points) ______I______
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Total (100) Points ______I______
Final Score %age ______
Name ______
CE 321 - Introduction to Environmental Engineering
Exam II
November 17, 2004
Print your name at the top of this page. Initial this page and all subsequent pages. All work is to be done neatly using a dark pencil or pen. Answers are to be underlined or boxed. All assumptions are to be addressed. SHOW ALL WORK!!!!
Problem 1 - (40 Points)
The town of Martins Creek, PA, has filed a complaint with the Department of Environmental Protection (DEP) citing the town of Portland, PA, for the discharge of raw sewage into the Delaware River. The raw sewage is considered to be the cause of high fecal coliform counts and reduced levels of dissolved oxygen (DO) which have lead to foul odors along the river between Portland and Martins Creek. The coliform counts and reduced DO levels have lead to restrictions of recreational areas within the Portland/Martins Creek reach of the Delaware River.
The DEP water quality criterion for the Delaware River is 5 mg/L of DO (i.e. at no point shall the DO concentration drop below 5 mg/L).
Martins Creek is 15.55 km down stream of Portland.
A) What is the DO concentration as mg/L at Martins Creek? (35 Points)
B) Does your answer make sense based on the complaint received? (5 Points)
The following data pertain to the 7-year, 10-day low flow at Portland
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Parameter Wastewater Delaware River just above Portland
Flow (m3/sec) 0.1507 1.08
BOD5 at 16oC (mg/L) 128.00 Not provided
BODu at 28oC (mg/L) Not provided 11.40
DO (mg/L) 1.00 7.95
k at 20oC (day-1) 0.4375 k of BOD in river is based on WW
Temperature (oC) 16.00 28.00
Data of river after WWTP
Average Speed (m/sec) N/A 0.390
Average Depth (m) N/A 2.80
Bed-activity coefficient N/A 0.200
A) What is the DO concentration as mg/L at Martins Creek? (35 Points)
Problem 2 (10 Points)
If the dissolved oxygen concentration measured during a BOD test is 9 mg/L initially, 6 mg/L after 5 days, and 3 mg/L after an indefinitely long period of time, calculate the 10-day BOD.
Problem 3 (10 Points)
The pH of two liters of deionized water is adjusted by adding 5 ml of a 0.05 mM solution of H2SO4.
50 grams of ferric sulfate (Fe2(SO4)3.5H2O) is added to the two liter beaker of pH adjusted deionized water. The pH is held constant through additional titration using acid and base as necessary.
What concentration of Fe+3 would you expect to find in the beaker after the solution reaches equilibrium? Report your answer in mg/L.
Ferric Hydroxide - pKsp = 38.57
H = 1.00 g/mole; S = 32.07; O = 16.00; Fe = 55.83 g/mole
Because Fe is a sparingly soluble salt of OH, as the Fe2(SO4)3 dissolved only a very small concentration of Fe would stay in solution. Any excess would precipitate out as Fe(OH)3. It is assumed the ionic concentration due to the sulfate will not play any role in the system.
Short Answer Section (35 Points)
Keep written answers to a sentence or two! Use diagrams when appropriate.
1) Briefly explain what type of particles do not settle out by gravity and why. (3 Points)
2) Regarding pH (Use chemical and/or mathematical relationships to explain) (5 Points)
a. What would you expect the pH of a typical soda, such as Coke or Ginger Ale, to be and why? (3 Points)
b. Would you expect to happen to the pH of soda after it is been opened for a few hours? Why? (2 Points)
3) The Streeter-Phelps model has a number of different variables, each variable playing a large role in the outcome of the DO deficit (D). (8 Points)
a. Increasing the reaeration rate, while holding everything else constant does what to the deficit (Dt) and the critical point (tc)? (4 Points)
b. Decreasing the deoxygenation rate, while holding everything else constant does what to the deficit (Dt) and the critical point (tc)? (4 Points)
4) Briefly discuss the impact of the following nitrogen compounds in surface water when occurring in high concentrations. (8 Points)
a. Nitrate (NO3-) (2 Points)
b. Ammonia (NH3) (2 Points)
c. Ammonium (NH4+) (2 Points)
d. Organic Nitrogen (2 Points)
5) Why is EPA justified in recently reducing the allowable amount of turbidity from 0.5 NTU to 0.3 NTU in drinking water? (5 Points)
6) Draw a detailed ”Solids Analysis Chart” starting with sample passing through a 1.2 um filter. (5 Points)
7) How does conductivity relate to “Water Quality” assessment? (3 Points)
8) What is the difference between BODt and Lt? (3 Points)
Formula Sheet - Exam II
1) Density of water = 1000 kg/m3 = 62.43 #/ft3
2) 7.48 gal/ft3
3) 8.34 #/gal
4) 1000 L/m3
5)
6)
7)
8)
9)
10)
11) = 4.45 x 10-7
12) = 4.69 x 10-11
13) H2CO3 <==> H+ + HCO3-
14)
15) Lo = Lt + BODt
16) Lt = Lo e-kt
17) BODt = Lo (1 – e-kt)
18) kt = k20 θ(T – 20)
19) NBOD = (4.57 mgO2/mgN) ( X mgN/L)
20) BODt = Lo(1-e-kt); when considering stream activity then BODt = Lo(1-)
21) Lt = Loe-kt ; when considering stream activity then Lt = Lo
22) , θ for k and kd; 4-20oC = 1.135 and 21 – 30 oC = 1.056: θ for kr = 1.024
23) kd = Where k = BOD rate constant. Unit specific k = d-1;u = m/sec; h = m
24) Unit specific u = m/sec; h = m
25)
26)
27) When kr = kd Then D = (kdLot + Do)
28) When kr = kd Then tc =
29) Dt = DOs – DO
30) Do = DOs -
31) Lo =
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33)
34)
35)
36)
37)
38)
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