A new house is build 2000 ft from the site of an abandoned dry cleaner. 10 years
ID: 1823144 • Letter: A
Question
A new house is build 2000 ft from the site of an abandoned dry cleaner. 10 years ago, during the last year of operation, the dry cleaner dumped 10 gallons of tetrachloroethylene (PCE) into the aquifer. PCE has a density of 1.622 g/mL and a solubility of 0.15 g/L. the aquifer has a hydraulic conductivity of 100 gal/ft2-day, an area of 500 ft2, a porosity of 0.35 and a hydraulic gradient of 0.008a. the PF of PCE is 0.051 (mg/kg-day)^-1. Calculate the MCL for the acceptable risk of 1/10^6 (ans. 0.686 ppb)
b. how long will it take for the PCE to reach the well at the new house (ans. 18 year)
c. the water is pumped out of the aquifer at a rate of 2000 gpd, treat it with activated carbon and then put it back into the aquifer. At the flow rate how long until al the PCE is removed, assume carbon removed 100% of the PCE (ans. 54 days)
Explanation / Answer
a. The oral potency factor (PF) of PCE is 0.051 (mg/kg-day)-1. Calculate the MCL for the acceptable risk of 1/106. (0.686ppb) 6.86e-10 g/L Dose=risk/PF=?10?^(-6)/0.051((kg-day)/mg) =1.961x?10?^(-5) mg/(kg-day) MCL=dose*Weight/consumption=1.961x?10?^(-5) mg/(kg-day)*70kg/(2 liters/day)= =6.863x?10?^(-4) mg/liters (ppm)=0.686ppb b. How long will it take for the PCE to reach the well at the new house? (18 years) time=distance/v^' =2000ft/[((100 gal?(ft^2-day ))/0.35)*0.008] = =875 (ft^3-day)?gal x 7.48 gal?(ft^3 )=6545 days =17.932 years c. To treat the aquifer the engineers propose to pump out the water from the aquifer at a rate of 2000 gpd, treat it with activated carbon and then put it back into the aquifer. At this flow rate, how long until all the PCE is removed? Assume the activated carbon removes 100% of the PCE (54 days) time=(?_cont V_cont)/(C_cont Q)=(1.622 g?mL*10 gallons)/(0.15 g?L*2000gpd) =.054 (g-day)?mg*1000 mg/g=54 days
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.