ENV4001_s11_q3a_soln - ENV 4001 ENVIRONMENTAL SYSTEMS ENGINEERING Spring 2011 University of South Florida Quiz#3 Civil& Environmental Eng

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Unformatted text preview: ENV 4001: ENVIRONMENTAL SYSTEMS ENGINEERING Spring 2011 University of South Florida Quiz #3 Civil & Environmental Eng. Wednesday, April 27 Prof. J .A. Cunningham Instructions: 1. You may read these instructions, but do not turn the page or begin working until instructed. 2. This quiz contains three questions, each worth 20 points. Answer any two Questions. The total points possible are 40. 3. If you answer all three questions, make sure it is very clear which two you want me to grade. Otherwise, I will grade whichever two I choose. It might not be the ones you would have selected. 4. You will probably score higher if you focus on only two questions, rather than trying all three. It is not likely that you will have time to do a good job if you try all three questions. 5. Some questions might have multiple parts. The point value of each part is indicated. 6. Unit conversion factors, as well as other potentially—useful information, are provided on the back of this page. 7. Answer each question in the space provided. 8. Show your work and state any important assumptions you make. I cannot award partial credit if I can’t follow what you did. 9. Report a reasonable number of significant digits in your answers. 10. Include units in your answers. An answer without proper units is not correct! 11. You are allowed to use your textbook, your course notes, or other printed materials. You may not receive help from another person. 12. A hand-held calculator is recommended. Other electronic devices are not permitted. 13. Time limit: 40 minutes. Stop working when asked. If you continue working after time has been called, you will be penalized at a rate of 1 point per minute. 14. Don’t cheat. Cheating will result in appropriate disciplinary action according to university policy. More importantly, cheating indicates a lack of personal integrity. 15. Please print your name legibly in the space provided below, and turn in this quiz at the end of the period. 16. Hints: o Read each question carefully and answer the question that is asked. a Watch your units. If you take good care of your units, they will take good care of you. 0 Work carefully and don’t rush. Even ifyou can’t finish the quiz, you usually will score higher if you perform well on one or two problems, as opposed to performing badly on all of them. p 1/9 Potentially useful constants: Ideal gas constant, R: 8.314 Pa-1113-11101710K’1 = 82.06x10’6 atln'r113'mt)l"l-I{_i Gravitational acceleration, g: 9.81 111/52 Molecular weight of water, H20: 18.01 g/rnole Density ofwater at 25 0C: 09970 g/rnL : 997 kg/m3 Viscosity of water at 25 CC: 0.89081073 Pa'sec Density of air at 25 0C: 1.18 kg/m3 Viscosity of air at 25 DC: 1.85><10_5 Pa'sec Potentially useful conversion factors: Pressure: 1 atm : 760 mm Hg = 760 torr : 101325 Pa Mass: 1kg21000g=106mg=1090g Length: 1km= 1000111: 106 mm =109 um Temperature: 25 0C = 298.15 K Volume: 1 m3 = 1000 L : 106 mL = 106 cm3 Other : 1 Pa = 1 N/m2 = 1 kg/(m'sec2) 1 MW=106W =1061/s=106N-m/s Atomic Masses: H = 1.008 g/mole C : 12.011 g/mole N :14007 g/mole O = 15.999 g/mole P = 30.974 g/mole S : 32.06 g/mole C1 = 35.453 g/mole Br = 79.904 g/mole Na 2 22.99 g/mole Mg = 24.31 g/mole Ca = 40.08 g/mole Fe = 55.85 g/mole Equilibrium Concentrations of Oxygen (02) in Fresh Water (air/water equilibrium): Temperature Equil. Cone. of 02 Temperature Equil. Cone. of 0; (0C) (mg/L) cc) (mg/L) 10 11 33 21 8 99 11 11.08 22 8 83 12 10.83 23 8 68 13 10.60 24 8 53 14 10.37 25 8 38 15 10 15 26 8 22 16 9 95 27 8 O7 17 9 74 28 7 92 18 9 54 29 7 77 19 9.65 30 7 63 20 9.17 31 7 51 p 2/9 This page is left blank intentionally. First question begins on the back of this page. p 3/9 1. Consider a wastewater treatment plant that processes 10 million gallons per day (1577 m3 /hr) of municipal wastewater. At this plant, secondary treatment is performed via the activated sludge process, which we studied this year in ENV 4001. There is an aeration basin in which bacteria metabolize dissolved organic carbon, and there is a clarifier in which the biomass is separated from the treated effluent. Here is what we know about the secondary treatment at the plant: 0 The plant produces QW = l m3/hr = 24 m3/d of waste sludge. o The concentration of suspended solids in the treated effluent stream (which exits from the clarifier) is XE = 5 mg/L. 0 The concentration of dissolved organic carbon in the treated effluent, expressed as BOD5, mS=5mgL o The average hydraulic residence time in the aeration basin is 9 = 1 hr. 0 The bacteria that remove the BOD from the wastewater have the following biological properties: 0 half-velocity coefficient, KS = 60 mg/L BOD5 o bacterial death rate constant, kd : 0.10 d—1 0 maximum specific growth rate constant, Minax = 3 d—1 0 yield coefficient, Y = 0.6 mg of biomass produced per mg BOD5 consumed a. (16 pts) You want to maintain a biomass concentration X = 2000 mg/L in the aeration basin. What must be the concentration of biomass in the Sludge return stream, XR? Hint #l: The way to solve this problem is with a material balance. However, it is not obvious what control volume to use for the material balance. I recommend drawing your control volume around the entire secondary—treatment process, then balancing the mass of bacteria. Hint #2: Watch your units! ~ " ' '* ' ’ r“ -' m w -—- « MN":- problem 1 continues 9 . continued a. more Space to work on part a ACCUMJ‘SC-Ttbnr Flow '1” " Flu- Du 4' Shard? - Shari Stfifififi'j'fifih =3 OCLuMukuTeZM "=0 Flu; {A "'5 low LaMPa-ffink +8 PrbAvL-hw‘; fi‘gluw Ref“ H c f AHEKMRTE MEI-H DD 1 sum: fl’JJfi-x‘l'g R “W the “ my“ man: a. 1m pram Mi SP—T. TLC-+6 011. HW IT {5: Snafu; I: V t x = V/‘Amnc 5*‘63 X g i k 0 AP! m = rwm fat-H " A = - Sinks: VRMAL ‘—' V ltd X 3“ fl SQT: J = ' 3 V36 0 "’ - [Ob XE '+ 0“ KM] + [flh‘d’x S‘TY—i k“ L, = 05 X5 4‘ Gut“, : i“ (.3 Zn. “We, m up. Xi. w “35% ‘ (3T1 m 5 -- (ma, "Vb-r»? "311.) + (1 “WM. 364 efiusa‘éiv {of 0M UALflnufl E saw {or X“ =5 xu= ‘iaaf‘fi/L Q“ I Xrfi la. = 4303’JL fi ‘lSv-a “3.11.. i m TV: has “his are eqe'tvalm't. I MR.» 1k mé‘cunl 5AA”: ogemaw, m a. 33-: Amanda .1 fine. to. V = 60: ’ “5031': "‘18: I377 «3 GE: “El/Eur (9w: lMgl‘k, = N‘s/d 2H F‘s/d - 9300 L. b. (4 pts) Does the value of X R that you found in part a appear reasonable? Why or why not? What would you typically expect for a value of XR? (“‘5 V539“ I“ Willi Fmsonuble. We dl’Tfln 5“, a Shela: rat-m s’l'f‘un. T“ 1‘” M‘jLL’PLM" a; clroou “JIL- 10,000 mi}. so '11:; 96am; gt r: LT. NOTE: 11‘ is 91.5;th '13 Solufi {at Q“, 1% Slucific mtrn r1112. 3* “UM oi? To Be Luci all” what is 2'77, «I 1k helium “we Vita-~45. m “gun‘le Tm g; Afi.‘ nquireé fir 1k pr»be ‘ofl 1“” it a m. clam. M1”: mark. p5/9 2. This semester, the students in my graduate class (ENV 6519) are designing several technologies to clean up a site that has been contaminated by trichloroethene (TCE) and cis- dichloroethene (cis—DCE). In one part of the project, the students have to treat an air stream that contains these two contaminants. The air stream is at a temperature of 31 °C and the flow rate is 0.38 m3/s. Here are some properties of those two chemicals and the air stream: Molecular Molecular Henry’s Concentration formula weight constant in air phase at 31 °C (mg/m3) (dimensionless) TCE cis-DCE CzHClg 131.39 0.528 40 C2H2C12 96.94 0.218 10 a. (10 pts) The students in ENV 6519 will treat the air stream with granular activated carbon (GAC), a technology that we did not consider in ENV 4001 this semester. To design the GAC system, the students must convert the contaminant concentrations into partial pressures. Estimate the partial pressure of T CE and eis-DCE in the contaminated air stream. Report your answer in units of Pa. n ?V: Ail-f :5 a ‘Q‘ RT 11, . (“‘55 w- : 4W .,, a (ME r 2A W V “$54M Lu 3‘” \hhwl Mei-r Lamar"? EL :- 40 Mfi TEE-I l 2 imam M -4 “6195/ 3 LE" “ m3 w * moo m5 ‘* my, 3 - 3.0%50 m -—i “‘5 ~fln3 'Y: (3.0‘isédfi lei/QBCSfiU—l, EEETBCEH l4) 3 0.77 ?a_ “W 1r.) '9‘ _ ‘0 finfi ctr—ME l 5 ifaqigl. at .7 I “.1 Malu/ 3 (it'll/“(E‘- V " M; Mr 3* t w 5.0 is m b [one m5} WM“ 3 P: (1.0%“? Mu/fifisw a} = 0.3.59 (Ra. m problem 2 continues 9 p 6/9 2. continued a. more space to work on part a { '- énmiiéa La Prat) gammm\ +9 TWT "iLEM Cod—amihmfi'; L‘th Gfitf, («a 0-5.,ch A0“ “fl sari» 94‘ fl-fi-t‘ QTfiJAjin‘ and} “M GM wince, Tate, am: 032% at 49. mm "ts learn how Tu (“Sign saga”; "'1‘"; the». JP Lord‘tkmiqaff‘i grouatiw'flgr and .5ng b. (10 pts) Suppose you wanted to treat the contaminated air stream with a hiofilter rather than With GAC. Assume that, in the biofiiter, the biodegradation rate of cis-DCE is twice as high as the biodegradation rate of TCE. If you design a biofilter that can treat TCE to an effluent concentration of 5 nag/mi what will be the effluent concentration of cis-DCE? , 2 it. BioLi—Efi removal gamma rYL= l-cxp — Uh] {3mm "tut emit. m3 TCE, (EMD‘J9\ (“manna = 1" :3 (1:1,; = 0-615- __ E 3i. Zk _.-. ._ \m we inane; 0.51:: l-flxifi,‘ 0%] '3) Wu K“ =— 2.9% {H We Gwen in (S Twig 93 1H3!" Ar aés- M59 me Can see 116* K“ '15 late?! iv CisebCE 0.21: v: 0.523? mm 3) u mi“ TLe mm, ‘i‘br brfin anemia.“ 0.51% "(we in? Hid-$303, % ‘= (2.033CL5( (lbs : p.07 "1‘: \‘Ekgi‘lmfl‘g :- ‘—5 citififlgél. [mwal WW M iv Q‘s-W '- (moooowxwiffi‘;= am)” “in? W = OH}. flfi/mfi p 7/9 3. The University of New Hampshire (UNH) produces about 85% of its own electricity in a campus power plant that burns methane. The methane is collected from a landfill in Rochester, NH, and then piped underground to the UNH campus. UNH is the only major university that meets its electricity needs with landfill gas. Let’s make the following assumptions: 0 The landfill in Rochester collects municipal solid waste (MSW) and serves 100,000 people. 0 The landfill is able to capture about 75% of the methane produced in the landfill. 1 don’t know if these assumptions are correct, but they seem reasonable. a. (10 pts) How much electricity (in units of MW) do you expect UNH can generate from the landfill gas? Clearly state any other assumptions you make. this ‘:' Tagf =3 0'5"“1, 2'0 O! 000 ké/A M5 w flaydfi"; LQT’S “SSUML 9/. FlfflC‘l—d, '737. % lgulbw \kflA'Ft-“flcl From “W l0 we llama.) \ \cj MSW Freda-aw: 9M; Mu; Mpi'rvwné. “50,000 Mk" 1‘ NDL‘U I; ifi%xg0’:¢ “ML” Cliu/ all ‘45 9951M W ‘ Cl s WA“ alts. 515‘ ASJUME 73/» wlhtfié =39 (lb—{Stu}: t I /d Hair VRKUL DP 5 $510 kj/thogfiw £03m “U ma‘n‘i :1; t ' \I been: 'fifi‘xt‘toEB—e maul “fa tat-mi is amt Marta; flSSuW‘L picks—i, lit “If! e (o.1§)(f,.tahto% *3/53 = 52.81103 W/A a is; [.1 at...“ ‘ has. 1% ' QMS‘HD d 3 lug Lr T3th 5} 1000 L3 = problem 3 continues 9 p 8/9 3. continued b. (10 pts) Suppose that UNH is responsible for treating the leachate that is produced by the Rochester landfill. Further suppose that it takes 1 kWh (kilowatt-hr) of energy to treat 1,000 liters of leachate. What fraction ofthe UNH electricity must go to leachate treatment? Does it seem tolerable, or is it unacceptably high? Clearly state any assumptions you make. 3,5 M = 18w kw & 2533‘: .7. Sqfiwéhfi wormed! gt out-t How {huQL‘ lac-still Pruinceni? ramp “41—?” star is amass-a 06th mm is east. amputee, Ml 31.3% at smartest. smelt“ {5 mafia”, a; Sum in WA to (Homo-C) Egt‘flob'lfixtafilés '5 32,900 lfi/d (“Adi Pmfiaui HonU, saw; with i3 usui én pmémf‘tm s??- CHH COL NH} “P m up 41. we: raga/k3 W l‘fllt mm “Eb/L3 mu) (£0,009 k5 mailbox Vinita-)0 \b/rma) ’- — m Etax'LLfomufmfi ;« it» to H, Lib!) hub/é tutu {banned “it \‘c‘d‘tr 9”“3‘.“ "~ 31,0013 ka/J " lLLlou 19!; = llfioo ham = 21,10; “Li _L_ 1 hwk km 1mm 3 It looo 1. =—‘> 11.1 —*-a\ “flares 4:”, uaLLgtt +rth-t- . \LWlnid n3 7113A 2‘1 m " 0 Stem like 5 r.“ #0451134 smoo Lot/a Palm ' 0'0 * - "- W1 M I “flaw IT I: «cap‘fihlt. ENDOFQUIZ p 9/9 ...
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This note was uploaded on 06/12/2011 for the course ENV 4001 taught by Professor Staff during the Fall '08 term at University of South Florida - Tampa.

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ENV4001_s11_q3a_soln - ENV 4001 ENVIRONMENTAL SYSTEMS ENGINEERING Spring 2011 University of South Florida Quiz#3 Civil& Environmental Eng

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