exam2fall07sol

exam2fall07sol - CEE 3104 (Mm) Exam 2 2007.11.01 HONOR CODE...

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Unformatted text preview: CEE 3104 (Mm) Exam 2 2007.11.01 HONOR CODE I have neither given nor received unauthorized assistance on this exam. Name Signature last, first Potentially useful equations _ @552 -= [41:95! E? = 4“ co/_c(BW AT] R1sk (CDI)(SF) Rm dt kC =>C(t) Coe 1 '1 4 = - — k 1/2 = (T-20) Cout=Coe°+Cin[1'e°i CM C°eXpi (19* it] 19:39" kr kzoe H3/2 BOD, = M P = vs/Vtot L, = Loe'k’ L0 = BOD, + L, BOD, = L0 (1 — e'k’) = M (e—kdt _ e—krt )+ Due-k» ,c = 1 1n{_lgr_[l _ Da(kr — m} [6, - kd k, — kd kd dea Physical constants Molecular masses H = 1.01 g mol'1 C = 12.0 g mol'1 N = 14.0 g mol'1 0 = 16.0 g mol'1 F = 19.0 g mol'1 C1 = 35.5 g mol" Water density pm = 1000 kg m'3 = 1 kg L'1 = 1000 g L'1 = 1 g ml" = 1 g cm’3 Conversion factors Length 1m=3.281 ft 1km=0.6214mi Volume 1 m3 = 1000 L 1 113 = 0.02832 m3 1 gal (US) = 3.785 L Mass 1 lbm = 0.4536 kg Temperature K = °c + 273.15 °C = 5/9 * (°F — 32) Normality l meq L'1 = 50 mg L'1 as CaCOs Pressure 1 atrn = 101,325 Pa lof8 WWW' w—Wmfi.__w, r, , SHOW YOUR WORK! You do not have to answer in complete sentences. 1) In the movie A Civil Action, residents of Woburn, Massachusetts sued a chemical company for contaminating the water with trichloroethene (also known as trichloroethylene) and causing high rates of childhood leukemia. The EPA has withdrawn its cancer potency slope for oral exposure to TCE due to insufficient evidence, but it reports a cancer potency slope of 0.006 kg day mg'1 for inhalation exposure. a) (8 points) Determine whether exposure to TCE during bathing might have been ' - - or the cancers. Measurements in well water found TCE concentrations of ' which according to Henry’s Law, would produce a concentration of air if the water temperature were 100 °F. The child takes a bath every day for 15 min. Other exposure parameters are provided in the table above. What is the child’s CDI of TCE due to inhalation and dermal exposure during bathing? lawman = C3” : C = M ’5 “33/0! [5 min m3>( ) min) : 0: \ _.———-—~ OOOL .. me 0000 "1 '0.ng "1413“) '79)) 19% CD! (0.2 L) 0 (I‘m mm 3of8 b) (6 points) What risk does the child incur due to inhalation exposure to TCE in air during bathing? Is this value of concern? (/hch aposwe risk: CPI '5’: = (0,7,2 fidxaoao fi):lz.7xm-zl We. Vafim rs 9NWW W, £19,415 Mere/me, of" 1x10", 50 yes, I7 15 of Cancun. c) (6 points) Arsenic has also been found in wells in the area at concentrations of 70 pg L'1 s us If the oral cancer potency slope for arsenic is 1.5 kg day mg“, what is the chi] ’ from exposure to drinking water? (70 % (re/MM N iii—43> mm} 2% (ar er “W k TCE “5 1‘ dgfioims) Naine one slte “in risk assessment. @ ex W S Um a 5 355 W @‘WXICAU (ddsev-Pegmgg)~fesfiry @ risk Warm/zafm e) (4 points) Is mutagenesis considered an acute or chronic effect? Charm 6, f) (4 points) How is the RID related to the NOAEL? : Mama, sappny a? 4of8 2) You have been conducting a water quality study of Lake Nanhuatzin, which has a surface area of ' = I ‘ X 105 m2. The average depth of the lake is so its volume is The lake is fed by a stream having a flow rate 0 Q = 1.02 m3 s'1 and a p osp orous concentration of C, = 0.023 mg L". Runoff from the homes along the lake adds phosphorous at an average annual rate of m, = 1.25 g s". (Hint: this is a mass flow rate that is already in terms of Q,C,.) A river flows from the lake at a flow rate of Q0“, = 1.02 m3 s". The average phosphorous concentration in the lake is C = 13.2 pg L". The lake’s volume remains constant over time. Phosphorous removal is caused by gravitational settling and can be treated as a first-order reaction where the settling rate is essentially the rate coeflicient, k, in units of inverse time. a) (4 points) Write the mass balance equation describing the rate of change of mass of phosphorous in the lake using the terms in the problem statement above. Your equation may also include t. 9159’): QSCs-l' ’Y'lr’ QM C“ kCV We b) (8 points) What is the'rate coefficient that describes the loss of phosphorous? L - L aha“: = [010% ‘ 010 3' Ce- m I’i? (1000/13): 0.0132 ’3 v: 8% (o6 m 3 (L339) = sax/0" L ((020 ‘75)(0023 trams-o @ ~(zozo aroma LE?) (0.0137 '-."i*)( @0sz L) :[.1X(0‘/S(Kéioags)=/lro3 /0l c) (4 points) Why is phosphorous considered a pollutant? 1+ Is at mace WCML Cash/‘9‘“ *0 excessug Qfigan gramme. th’bphJCaZTan.) and WW 0x on ld’oz‘r‘n. 50f8 k.— 3) According to a Washington Post article on 23 October 2007, raw sewage is flowing into the Anacostia River from a leak in a major sewer line that carries waste in Washington, DC. This question examines a similar problem on a smaller scale. The saturation DO at 20 °C is 9.17 mg L'l. M 30135 at 20 °C m L' m— m— a) (8 points) What is the ultimate BOD of the wastewater? govt = L, U— 6'”) 30171: {28 "34 “(at =Wx5¢o = M4 "3L Lulu) :- b) (6 points What is the ultimate BOD at the discharge point, just after mixing? mass lo Meg, an Lo 6d discharg 6 Point": d( a - QwLWerLm‘f/Qa Lam 0H: QwL-alw‘r Qt L—OV Lo, 01. : “"fi/J a a (0W) l .29 .213 j -—- 6of8 Wmmq—r .,_.,......w._,___ w...“ 7w” 7 m.” . .7 m, c) (6 points) What is the DC at the discharge point, just afier mixing? Mass \aaflaMce, srmZar +0 par'f“ Cb)’ Dfl : W DOW + gr D0; K 62a. z (0.25 @(I "13% (11%)(2 m.) (‘2'; g3 = 71¢ [all d) (20 points) What is the critical DO? Space for this problem continues on the next page. Qu' ’2 (DEM kr: IO: Eme’li 3.9(0/1‘0) : 0'52 2,83" @FM Da- mammal:— 6117—719 = 20; MyL - ___I, k ’ Dq(kr"l<d) i @F’M’ ‘tc: {cfkr'kd InifiD [Wu]; J“ oi“ 1 0.526-0Hlf/d In {0.44 ' (My (213) J a ms 0, {1,H5[O.018é]} = 1.90 at m4 4%“ Jeri: 4ft @Fmd Dc: Dsmk '6 +Q5 C .— ‘5' I (034x273) (6‘(awwgéaszaafioy+ 2‘0, 6 a 2W) I ’ (0.0%) .. 139.7(O.93§'o.365’)+ 0.790 :- 482 "z @ fir/Ad D06; DQ:m'DC:9r/?~ q—Ww- VW-MW._W NV. V V, Tn ream}, "HM; D0 canmo+ be less than 1w, qudafim 1001416! S/aw (M133 e) (4 points) How far downstream does the critical DO occur, in km? m m = (m Maw aways); és 6&4 m :1 66 km f) (4 points) Draw the oxygen sag curve on the axes below. Label the axes and important features. 'i: (a!) g) (4 points) What two processes contribute to determining the rate of change in oxygen deficit?demygmm (blomflm Mal Namm 80f8 ...
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This note was uploaded on 03/31/2008 for the course CEE 3104 taught by Professor Lcmarr during the Spring '07 term at Virginia Tech.

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exam2fall07sol - CEE 3104 (Mm) Exam 2 2007.11.01 HONOR CODE...

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