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ex 2 sol - Introduction to Environmental Engineering(CE...

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Unformatted text preview: Introduction to Environmental Engineering (CE 3501) EXAM 2 4f2J'09 Name Note: State all of your assumptions. Make sure you Show your work and that it is easy to follow. PART A: SHORT ANSWER, 8 points each 1. You have reached equilibrium in a chemical reaction when: The rate of the forward reaction equals the rate of the reverse reaction 2. List 3 reasons that were discussed in class as to why bacteria are important. Agents of disease, critical for global nutrientfelement cycling, they decompose waste (wastewater treatment, hazardous waste clean-up) 3. a. What nutrient tends to limit growth in marine systems? b. Give a specific location where this has become a problem. Nitrogen; Gulf of Mexico 4. Write Darcy’s Law for groundwater flowrate (Q) below (clearly and accurately define your terms). Q = KA (dhde) K is the hydraulic conductivity, A is the cross-sectional area, h is the hydraulic head, and L is the distance between the locations for which the head is known (or dhldL is the hydraulic gradient). 5. Sketch (NO words necessary) the temperature profile of the air with distance above the earth during an inversion on the graph below. The dry adiabatic lapse rate is shown as a dashed line. \ Inversion from | here up Inversion over whole distance Distance above the earth —* Temperature __’ PART B. PROBLEMS l. (20 pts) A truck containing industrial waste was found abandoned on a country road. A date on the waste containers shows that it was produced 3 days ago. You analyze the water in the truck and find that the BOD5 is 200 mgz’L and the reaction rate coefficient is 0.1 day']. You know the ultimate BOD of the waste produced by all of the area industries (given below). Which of the industries produced the waste (give the name of the industry and support your answer with the appropriate calculations)? Industry Ultimate BOD (lggfli) i Blankfige Paper Mill 330 Foot and Mouth Feedlot 363 l Dwa—Us ‘ 508 I Pint o’ Ale Brewei _6_86 I_Fabulous Fran’s Fruit Filling Plant | 1961 Show your work dearly and neatly Roby: {MCI-5% (out Lo at; «to draw (20 pts) A stack emitting 20 gfs of H2X has an effective stack height of 80 m. The windspeed is 3 mfs 10 m above the ground surface. Estimate the ground-level H2X concentration directly downwind at a distance of 4 km given a “Class C” atmospheric stability classification (in ugfma). Show your work clearly and nearly; helpful tables are given on the fast page of the rest. lsj: 4i “07+" 9 P-sz. 14mm film’hfl lfih PM? :EL: [0 w— 665;!“3 w 90 w- “3”} fill—2 law/s (”be”) (20 pts) H2X is soluble in water and is also a weak acid. Unfortunately, HX' is very toxic to fish at concentrations above 0.001 M. Is there likely to be a toxicity problem in a lake located 4 km downwind from the stack if the lake pH is 7.8 (Answer yes or no and support your answer with the appropriate calculations)? What would the lake pH need to be for the concentration of HX- to NOT be at toxic levels (answer in pH units)? Given: Henry’s Law coefficient for HgX is 3.5 (molr‘L)f(ugx’L) Acid dissociation constant of H2X is 5.37 x 10'10 pi wannabe: CM : EHQ< Eff—2H0"? @ ...
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