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11.9 This problem allows you to think about how exposure impacts the concentration of
air pollutants you are exposed to. (a) Maintain a diary for one full day and record all the
locations you visit. Include the times of entry and exit for each location. Also record any
interesting air quality information for each location. Calculate the percentage of time
spent in each type of location. Summarize the data in a table. (b) In which location did
you spend the most amount of time? The least? (c) Calculate the 24-hr time integrated
average exposure concentration (units of µg/m3) to airborne particles based on your
recorded activity patterns, using the average airborne PM10 concentration for different
locations provided below.
Location
Average Airborne PM
10
Concentration (µg/m
3
)
Home
90
Office-Factory
40
Bar-Restaurant
200
Other Indoor
20
In a Vehicle
45
Outdoors
35
(a) (b) Students should be developing this type of table from the data entered into
their dairy for their 24 hour period. Their raw data from the diary can be attached
(d) Now add a 35 µg/m3 “proximity effect” to one of your locations above that we will
assume is from exposure to cigarette smoking at that location. How does this change
your 24-hr time integrated average exposure concentration (units of µg/m3) to airborne
particles?
Solution:
Students’ answers should vary.
11.10 (a) Define NAAQS and (b) identify the NAAQS pollutants.
Solution:
NAAQS is described in Section 11.4.
11.11 On January 12, 2013 the AQI in Beijing (China) the AQI was determined to be
775. In contrast, on January 11, 2013, Salt Lake City (Utah) has a reported AQI of 142
compared to a value of 67 in San Francisco's and a value of 23 in Las Vegas. Develop a
table with three columns. List the four cities, the AQI reported above, and the third
column should provide the level of health concern related to an AQI for general and
sensitive populations.
Solution:
11.12 The following data on U.S. population, number of licenses drivers, and number of
vehicles was obtained from the U.S. Department of Transportation, Federal Highway
Administration (http://www.fhwa.dot.gov/policyinformation/statistics/2010/dv1c.cfm).
(a) Determine the rate of growth (on a per year basis) for the population, number of
licensed drivers, and number of vehicles. (b) Are the rates of growth similar or different?
Solution:
11.13 A travel demand management action is planned that will add parking spaces to an
existing park-and-ride facility that is served by transit. The plan will add 120 parking
spaces. Assume the new spaces will have a 95 percent estimated utilization rate and
these individuals will use the available light rail and bus service. Also assume that the
average commute that will be eliminated is 42 miles roundtrip (distance from lot to
destination and return), and there are 250 operating days per year. (a) What is the annual
reduction in vehicle miles traveled from implementation of the park and transit ride
facility? (b) if the emission factor for reactive hydrocarbons is 0.23 grams/mile driven
and for NOx is 0.40 grams per mile driven, what is the estimated reduction in air
emissions for both of these air pollutants over the year?
Solution:
11.14 True or False? Compared to a baghouse with a high pressure drop, a baghouse with
a low pressure drop would need a large fan and require more energy to move the gas
through the baghouse.
Solution:
11.15 A baghouse that employs a shaker collection method is being designed to remove
99.75 percent of an incoming stream of sawdust particles originating from a sawmill
plant. What fabric area is required for the baghouse if it treats 15,000 ft3/min of polluted
air? How many bags are required if the bags are cylindrical and are 6 inches in diameter
and 15 ft long? Assume the filter manufacturer has specified a woven fabric.
Solution:
11.16 You are assigned to determine the number of filter bags required for an 8-
compartment baghouse that uses pulse-jetting as the method to remove particulate matter
from the bags. The following information is known: process gas exhaust rate is 100,000
ft3/min and the recommended air-to-cloth ratio is 4 ft/min. The bags specified by the
manufacturer have a diameter of 6 inches and height of 10 ft. (a) what is the total required
fabric area? (ft2)? (b) What number of bags is required? (c) How many bags are in each
compartment?
Solution:
11.17 A thermal oxidizer incinerator operates as a plug flow reactor at a temperature of
250oC and has a gas residence time of 0.3 seconds (a) If the pollutant (vinyl chloride)
enters the incinerator at a flow rate of 3,000 m3/min and it is desired to remove 99.99% of
the pollutant, what should the length of the incinerator be? (b) What is the length of the
incinerator if the desired removal is increased to 99.99995? The first order rate constant
for vinyl chloride removal is 45/sec at 250oC and the inside diameter of the incinerator
(which is shaped like a cylinder) is 1 m.
Solution:
11.18 A tubular thermal oxidizer is operated at 225oC to remove toluene (C6H7) from a
polluted airstream. The residence time for the gas is 1 sec. (a) Write the balanced
reaction for theoretical oxidation of toluene to carbon dioxide and water. (b) If the
toluene enters the incinerator at a flow rate of 2,500 ft3/min and the reaction rate constant
is 7.2/sec at this temperature, what percentage of the toluene is removed? (c) What is the
length required for the oxidizer if the inside diameter is 4 feet?
Solution:
11.19 A biofilter design uses a media that consists of a mixture of wood chips and
compost at a ratio of 1 to 3 parts wood chips to municipal compost. The biofilter has the
following dimensions, L = 8 m, W = 4.8 m, Depth = 0.35 m, and the air flow rate is 2.6
m3/s. (a) What is the empty bed residence time (sec)? (b) Using the Table provided in the
chapter that relates empty bed residence time to application, what application(s) might
this biofilter be appropriate for?
Solution:
b. From table 11.23, agriculture is the application this biofilter may be used for.
11.20 Calculate the (a) stack emissions and (b) fugitive emissions if some process
equipment that is associated with a hood system generates 220 kg/hr of VOCs, the hood
capture efficiency is 87%, and the collection efficiency of the air pollution control
technology used to treat the captured air emissions is 95%.
Solution:
97.5% efficiency. The plant produces 350 metric tons of sulfuric acid at 100% purity
every day. A wet scrubbing system is installed to reduce the SO2 emissions and has a
removal efficiency of 97%. The emission factor for this process equals 17 kg SO2/metric
ton of raw material processed. (a) What are the daily emissions of SO2 from the
manufacturing facility prior to treatment? (b) What are the daily emissions of SO2 from
the manufacturing facility after treatment?
Solution:
11.22 Assume the emissions factor for release of mercury from a solid waste incinerator
is 0.107 lb per ton incinerated and for dioxin is 2.13×10-5 lb per ton solid waste
incinerated. Estimate the daily emission rates (lb pollutant/day) and annual emissions
rates (lb/yr) of each of these hazardous air pollutants. Assume the incinerator processes
2.88 ×106 lbs of solid waste per year.
Solution:
11.23 Acetone is released from combustion of 100,000 metric tons of wood waste per
year. The wood waste has an average heat content of 0.05 MM BTU/lb. The reported
emission factor for acetone emitted from a waste bark fired boiler with no emissions
control is 9.5×10-3 kg/metric ton of wood burned. What are the annual emissions of
acetone from this facility (metric tons per year)?
Solution:
11.24 A company annually applies 25,000 liters of a surface coating to their product. The
surface coating contains the VOC, acetone. The emissions are collected and an
emissions control technology is installed that reduces the VOC emissions by 80%. The
company is required to report their emissions to the atmosphere if they exceed 3,500
kg/year. For this coating process operation, there is no loss of the coating compound to
the coating equipment and no loss to the system’s liquid or solid waste streams. All the
VOC applied is captured by the collection system prior to treatment. The Material
Safety Data Sheet reports that the surface coating product contains 25% by weight
acetone and the specific gravity of the material is 1.35 kg/L. Use a mass balance
approach to estimate if the company must report their air emissions to the state regulatory
agency.
Solution:
11.25 A company applies 21,000 liters of a coating every year that contains three VOCs;
0.26 kg xylene per liter of coating, 0.040 kg n-butyl alcohol per liter of coating, and 0.13
kg ethyl benzene per liter of coating. (a) What is the total mass of VOC in the coating
(kg VOC/liter of coating)? (b) Estimate the total mass of VOCs released to the
atmosphere every year (kg/year) assuming no collection or treatment of the VOCs takes
place. (c) What is the total mass of VOCs released to the atmosphere assuming that 8%
of the applied VOC is retained in a liquid wastestream and is discharged to the
wastewater treatment plant and the company installs some control technology which
captures and degrades 60% of the collected air emissions?
Solution:
11.26 A company performs measurements that show the VOC xylene is present in the
stack gas and the gas flow rate is 2,200 m3/min. The concentration of xylene was
measured exiting the stack on a weekly basis and averaged 0.62 kg/hr. The
manufacturing process runs 6,700 hours every year. If the reporting threshold for the
xylene is 3,200 kg/year, use the source measurements to determine if the company
exceeds the annual reporting threshold.
Solution:
