CE 529 Hazardous Waste Management
Problem Set No. 2
Due Date: March 7, 2005
1.
A key central objective in CERCLA is to determine and rank the various abandoned hazardous waste
sites that are life-threatening for quick remedial action by the federal government. Look up the
relevant section in 40 CFR 300 and provide a two-page summary on the hazardous ranking system
(HRS) and explain how hazardous waste sites are evaluated to be included in the National Priority
List (NPL).
2.
Solve Problem 5-21, page 322.
3.
A community near a Superfund site unknowingly used chloroform-contaminated groundwater for all
their household purposes over a period of 10 years before the contamination was discovered and
alternative sources of water were provided. Compute the number of cancer cases expected for this
community based on the following data below. Assume exposure through drinking, bathing and
inhalation.
Population of community
= 100,000
Average concentration of chloroform in groundwater
= 0.2 mg/l
Average concentration of chloroform in house air
= 0.01 mg/m3
Resident bathe once a day, length of each bathing period
= 15 mins
Daily drinking water intake
= 2 liters
Average adult body surface area
= 1.94 m2
Dermal permeability constant (for contaminated water)
= 0.002 m/hr
Dermal permeability constant (for contaminated air)
= negligible
Absorption of chloroform through lungs
= 100%
Inhalation rate
= 14 l/min
Inhalation retention rate
= 50%
Average adult body weight
= 70 kg
Assume that RfD and CPF for skin absorption is similar to RfD and CPF for inhalation, and inhalation
RFD is equal to oral RfD.
4.
One of the problems with the chlorination of drinking water is the formation of trihalomethanes.
These compounds are formed from the interactions of chlorine with humic material in water. If the
following halomethanes were identified, estimate the total risk from these chemicals assuming a
typical adult resident will live, on average, in a given housing area for 30 years. The drinking water
concentrations of various compounds are as follows. Discuss why the approach taken above is a very
conservative estimate of risk?
Compound
chloroform
dibromochloromethane
bromoform
5.
Drinking Water (g/L)
4
4
5
(i) Write down the vapor pressure, solubility and Henry’s law constant for benzene and dichlrobenzene
(at 25o C)
(ii) Based on the above vapor pressure, compute the saturated vapor phase concentration of benzene
and dichlorobenzene in mg/L of air.
(iii) Estimate the dimensionless Henry’s law constant for both compounds.
(iv) 60 mL of a solution containing 200 mg/L of benzene was placed in a 1000 mL bottle and capped
immediately. The bottle was allowed to equilibrate for 24 hours. Estimate the new aqueous phase
concentration.
(v) 10 mL of pure benzene (specific density 0.877) was placed in a 100 mL bottle along with 50 mL of
distilled water and capped immediately. The solution was allowed to reach equilibrium.
What is the concentration of benzene in the gas phase?
What is the concentration of benzene in the aqueous phase?
Estimate the final volume of pure benzene in the bottle after equilibration. State your
assumptions.
(vi) Repeat questions in (v.) for 10 mL of dichorobenzene (specific density 1.12).
6.
Estimate the linear Kd and Koc for the sorption of compound A onto a soil with 0.5% organic carbon
content. Six vials were used, each containing 10 g of soil and 0.5 L of varying initial concentration of
compound A. After allowing the system to equilibrate for 24 hours, analysis of the aqueous phase
showed the following results. Assume no losses.
Initial concentration (mg/L)
86
48
33
18
8.5
3.5
7.
Final concentration (mg/L)
2.5
1.5
1.0
0.55
0.25
0.11
In your position as an environmental engineer, your boss wants to know whether a given compound X
in a waste stream may be volatilize and cause air emissions problems. Before you can assess the waste
stream as a potential air pollutant source, you need to know the dimensionless Henry’s law constant.
Your colleague came up with the following method which will minimize analytical measurements, i.e.,
only measurements in the gas phase. Take two 100 mL bottles. In one bottle, add 40 mL of the waste
stream containing X and immediately seal the bottle. For the second bottle, add 60 mL of the waste
stream containing X and immediately seal the bottle. Allow the bottles to equilibrate for 12 hours.
The concentrations in the gas phase of the bottles were measured and were found to be 1.59 mg/L and
2 mg/L for the 40 mL and 60 mL waste stream bottles, respectively. What is the dimensionless
Henry’s law constant for compound X?