1. Imagine that you are designing a chlorination system for a drinking water treatment plant. The design flow rate is (1577 m3/hr). You must provide a free chlorine residual of at least 1.0 mg/L chlorine in order to protect against contamination in the distribution system. However, you can not exceed a free residual of 2.0 mg/L chlorine, because you are worried about the formation of disinfection by-products. You are given the following data (graph on next page) for disinfection of Giardia lamblia. The data were collected in a batch reactor, using a free residual C= 1.5 mg/L chlorine.

a. From the graph, estimate the first-order rate constant k(in min-1) for both base 10 and base e.

b. Suppose your chlorine contactor is a well-stirred cylindrical tank. The diameter of the tank is 10 m and the depth (height) is also 10 m. What is the average hydraulic residence time, in units of minutes? If the contactor behaves as a CMFR, how much removal of Giardiawould you get (i.e., what fractional removal)? Hint: be sure to use the proper rate constant kfrom part (a).

c. Now suppose you had three smaller cylindrical tanks. The diameter of each tank is 7 m and the depth (height) of each is also 7 m. Each behaves as an ideal CMFR. You arrange the three tanks in series as shown below. Compare the average hydraulic residence time of the series configuration (i.e., for the water to pass through all three tanks) to the average hydraulic residence time of the larger tank from part (b).

d. Assuming the series configuration, what is the overall removal of Giardiathat you will achieve?

e. Look up the primary standard for disinfection of Giardiaand report it. Do you meet the standard with one large tank (part b)? Do you meet the standard with three small tanks in series (part c)? Why?

1. Imagine that you are designing a chlorination system for a drinking water treatment plant. The design flow rate is (1577 m3/hr). You must provide a free chlorine residual of at least 1.0 mg/L chlorine in order to protect against contamination in the distribution system. However, you can not exceed a free residual of 2.0 mg/L chlorine, because you are worried about the formation of disinfection by-products. You are given the following data (graph on next page) for disinfection of Giardia lamblia. The data were collected in a batch reactor, using a free residual C= 1.5 mg/L chlorine.

a. From the graph, estimate the first-order rate constant k(in min-1) for both base 10 and base e.

b. Suppose your chlorine contactor is a well-stirred cylindrical tank. The diameter of the tank is 10 m and the depth (height) is also 10 m. What is the average hydraulic residence time, in units of minutes? If the contactor behaves as a CMFR, how much removal of Giardiawould you get (i.e., what fractional removal)? Hint: be sure to use the proper rate constant kfrom part (a).

c. Now suppose you had three smaller cylindrical tanks. The diameter of each tank is 7 m and the depth (height) of each is also 7 m. Each behaves as an ideal CMFR. You arrange the three tanks in series as shown below. Compare the average hydraulic residence time of the series configuration (i.e., for the water to pass through all three tanks) to the average hydraulic residence time of the larger tank from part (b).

d. Assuming the series configuration, what is the overall removal of Giardiathat you will achieve?

e. Look up the primary standard for disinfection of Giardiaand report it. Do you meet the standard with one large tank (part b)? Do you meet the standard with three small tanks in series (part c)? Why?