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.  

  2. 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?

    3.  

  3. 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?

    4.  

  4. 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.

    5.  

  5. SHORT ANSWERS
  1. What is the difference between primary and secondary regulations (in terms of the Safe Drinking Water Act)?
  2. What is the purpose of preliminary wastewater treatment operations?
  3. What is infiltraiton/inflow?
  4. List the elements of multiple barriers of protection in terms of drinking water treatment and supply.