Toms River in NJ is contaminated with TCE from two sources. One is farm land whe
ID: 873266 • Letter: T
Question
Toms River in NJ is contaminated with TCE from two sources. One is farm land where they buried thousands of drums of toxic waste that are leaking into the aquifer. The aquifer flows into Toms River at point A. The aquifer has a flow of 0.5 MGD and contains 50 ppb TCE.The other source is a chemical plant owned by Ciba Geigy. They discharge 5 MGD of toxic waste directly into the River at point B. The discharge contains a TCE at a concentration of 10 ppb. The water is distributed to the public at point C. The distance between A and B is 500 ft and the distance between B and C is 500 ft. The area of the river is 100 ft2 .The River flows at 65 MGD before point A and does not contain any TCE.
a. What is the concentration of TCE at point A? Assume that the TCE does not decay. (0.382 ppb)
b. What is the concentration of TCE at point C? Assume that the TCE does not decay. (1.06 ppb)
c. You are hired as an environmental expert witness. It is your job to determine the main source of TCE and determine who should be responsible to clean it up. Pick either the dump site or Ciba Geigy and write one or two sentences explaining quantitatively why they should be responsible.
d. Now assume that TCE reacts with a first order decay constant of 1 hr-1 . Calculate the concentration at point A. Assume that the control volume at A and B are both 1 MG. (0.279 ppb)
e. Calculate the concentration of the water leaving point B. (0.70 ppb)
f. The EPA determined that the water is safe to drink if the concentration is less than 1 ppb. Are you confident that they can drink the water at point C? Name one assumption that you made that you would check before giving your approval.
Explanation / Answer
(a)
Point A, pollutant flow rate Q1 = 0.5MGD
TCE concentration c1 = 50ppb
Point B, pollutant flow rate Q2 = 5MGD
TCE concentration c2 = 10ppb
Pont C, total flow rate, Qt= 65+5+0.5 = 70.5MGD
Concetration = (Q1*c1+Q2*c2)/Qt = 1.07ppb