assignment 3 soln

assignment 3 soln - CEE 2300 Environmental Engineering...

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CEE 2300 – Environmental Engineering Principles S08 1 Assignment 3 Solution Due Date: Monday, February 25 Total Points: 100 Instructions (20 pts) : You may work alone or in groups to complete the homework assignments, but you should solve each problem yourself and turn in individual solutions. If you do work in groups, write the names of the people you worked with at the top of the homework set. Homework solutions are due at the start of class. Problem 1 (5 pts) . Davis and Masten 5-1. Occupational hexavalent chromium exposure, Cr(VI) Given: concentration = 0.05 mg/m 3 in air; exposure: 8 h/d, 5 d/wk, 50 wk/yr, ages 18 to 65 Solution: Exposure = (65-18) = 47 years Inhalation rate = 20 m 3 /day Using the inhalation form of the equation in Table 5-8 (eq. 5-15) CDI = (0.05 mg/m 3 ) (20 m 3 /day) / (70 kg) x {(8x5x50x47 hr) / (70x365x24 hr)} CDI = 0.0022 mg/kg/day Problem 2 (5 pts) . Davis and Masten 5-7. Hexavalent chromium risk Given: concentration = 0.05 mg/m 3 in air; exposure: 8 h/d, 5 d/wk, 50 wk/yr, ages 18 to 65 Solution: Slope factor for Cr(VI) from Table 5-5: 42 kg·day/mg From Problem 5-1: CDI = 0.0022 mg/kg/day Risk = (0.0022 mg/kg/day) (42 kg·day/mg) = 0.0924 Problem 3 (5 pts) . An epidemiologic study yields the results shown in the 2x2 table below. Do the data support a positive association between the contaminant and the disease? Justify your answer with a risk ratio. With disease Without disease Exposed 121 225,000 Unexposed 320 775,000 RR = (121/225,121) / (320/775,320) = 1.3 > 1 Yes, data support a positive association between exposure to contaminant and disease Problem 4 (5 pts) . Davis and Masten 7-12. World consumption rate of coal in 1991 Given: world coal reserve will last 200 years Solution: Table 7-4: world coal reserves in 1998 = 25,700 EJ Annual demand = 25,700 EJ / 200 years = 128.5 EJ/yr (32% of current total demand) Better: annual demand = 25,700 EJ / 193 years = 133.2 EJ/yr (assuming an average coal heating value of 27.15 MJ/kg, 4733 Mt coal/yr)
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CEE 2300 – Environmental Engineering Principles S08 2 Problem 5 (5 pts) . Davis and Masten 7-13. Coal exhaustion with improved efficiency Given: coal power plant at 33% efficiency, raise efficiency to 40% Solution: From Problem 7-12: annual consumption rate at 33% efficiency = 128.5 EJ/yr Consumption rate at 40% efficiency = 128.5 EJ/yr x 0.33/0.40 = 106 EJ/yr
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assignment 3 soln - CEE 2300 Environmental Engineering...

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