CEE 370 Spring 1996

Exam #2

April 29, 1996

Each problem is worth 20 points.

1. A drinking water contains compound X. We assume that an individual (70 kg mass) will drink 2 liters per day of this water, and will not be exposed to compound X by any other route. Compound X is a carcinogen and has a potency factor of 0.05/(mg/kg-day). If the acceptable excess lifetime risk of getting cancer from this compound is 1 in 100,000, what is the maximum concentration allowable in drinking water?
2.

3. You are evaluating the use of activated carbon for adsorbing Naphthol from water. Freundlich isotherm values are K=100 mg/gram, and 1/n=0.31. For an initial concentration of 1000 mg/L of Naphthol, how much activated carbon should you use to obtain an equilibrium concentration of 1 mg/L in a 1000 liter batch reactor?
4.

5. An activated sludge system will be used to treat the wastewater from a food processing plant. It has the following characteristics; Aeration volume (V) = 1000 m3, mixed liquor suspended solids (X) = 2500 mg/L, and thickened underflow solids from clarifier (Xu) = 10,000 mg/L. The plant will operate at a solids retention time (SRT) = 10 days. How much waste activated sludge must be wasted each day to keep the SRT at 10 days?
6.

7. A 25-meter, 3-meter deep clarifier has an influent flow of 10,000 m3 per day. Compute the overflow rate and the detention time.
8.