## Info

provided at a rate of 1.12 m per m of water treated and that the detention time of the tank is 2.2 min. The power dissipation of the mixer is 3.24 hp. The pressure Pt at which air is forced into the diffuser is 256,920.02 N/m . The depth at which the diffuser is placed at the bottom of the tank is 2 m and the barometric pressure is 101,300 N/m . What is the temperature of the water?

6.22 A hydraulic-jump mixer similar to the one shown in Figure 6.9 is used to mix alum in a water treatment plant. The height of the bottom of the sluice gate to the bottom of the channel is 5 cm. The mixing power developed is 1657.2 Nm/s and the width of the channel is 10 cm. Calculate the rate of inflow into the jump. The temperature of the water is 25°C and the downstream depth of the jump is 0.94 m.

6.23 A hydraulic-jump mixer similar to the one shown in Figure 6.9 is used to mix alum in a water treatment plant. The height of the bottom of the sluice gate to the bottom of the channel is 5 cm. The mixing power developed is 1657.2 Nm/s and the width of the channel is 10 cm. The rate of inflow into the jump is 0.048 m /s. At what temperature does the mixing occur?

6.24 A hydraulic-jump mixer similar to the one shown in Figure 6.9 is used to mix alum in a water treatment plant. The mixing power developed is 1657.2 Nm/s and the width of the channel is 10 cm. The rate of inflow into the jump is 0.048 m /s. The downstream depth of the jump is 0.94 m and the temperature of mixing is 25°C. Calculate the upstream depth of the jump.

6.25 A hydraulic-jump mixer similar to the one shown in Figure 6.9 is used to mix alum in a water treatment plant. The mixing power developed is 1657.2 Nm/s and the width of the channel is 10 cm. The rate of inflow into the jump is 0.048 m /s. The upstream depth of the jump is 5 cm and the temperature of mixing is 25°C. Calculate the downstream depth of the jump.

6.26 A hydraulic-jump mixer similar to the one shown in Figure 6.9 is used to mix alum in a water treatment plant. The mixing power developed is 1657.2 Nm/s and the downstream depth of the jump is 0.94 m. The rate of inflow into the jump is 0.048 m /s. The upstream depth of the jump is 5 cm and the temperature of mixing is 25°C. What is the channel width?

6.27 At a motor efficiency of 90% and a brake efficiency of 75%, the power input into a mixer was found to be 16,459 Nm/s. The average velocity gradient in the mixer tank is 1500s-1 and the temperature of mixing is 25°C. Find the volume of the mixer.

6.28 A suppressed rectangular is used to mix chemical in a wastewater treatment unit. The power dissipation developed is 7423.5 Nm/s. The length of the weir L and the height P were measured and found to be 2 m and 1 m, respectively. The temperature is 25°C. Determine the rate of flow through the weir, if HD = 2.5 m.

6.29 A suppressed rectangular is used to mix chemical in a wastewater treatment unit. The power dissipation developed is 7423.5 Nm/s. The length of the weir L and the height P were measured and found to be 2 m and 1 m, respectively. The rate of flow through the weir is 0.3 m /s and HD = 2.5 m. What is the temperature of the water?

6.30 A suppressed rectangular is used to mix chemical in a wastewater treatment unit. The power dissipation developed is 7423.5 Nm/s. The temperature is 25°C. The rate of flow through the weir is 0.3 m /s and HD = 2.5 m. Calculate the head over the weir.

6.31 A suppressed rectangular is used to mix chemical in a wastewater treatment unit. The power dissipation developed is 7423.5 Nm/s. The length of the weir L and the height P were measured and found to be 2 m and 1 m, respectively. The rate of flow through the weir is 0.3 m /s and HD = 2.5 m. The temperature is 25°C. Calculate the drop allowed HD.

6.32 For the problem in Example 6.5, determine if the power dissipated conforms to the requirement of effective mixing. Assume that mixing occurred in a volume of a rectangular parallelepiped of length, width, and depth equal to the length of the weir.

6.33 For the mixing in Problem 6.32, check if the process conforms to the criteria of effective mixing.

6.34 Redesign the mixer in Problem 6.33 if the operation does not conform to the criteria of effective mixing.

6.35 The power input into a compartment of a flocculator is 0.33 kW. The motor efficiency is 0.90% and the brake efficiency is 75%. The coefficient of drag is 1.54 and the paddle tip velocity is 0.55 m/s. The temperature in the flocculation tank is 20°C. Calculate the total combined projected area of the paddles. If the dimension of a blade is 0.18 m by 5.4 m, how many paddle blades are there in the compartment?

6.36 The power input into a compartment of a flocculator is 0.37 kW. The motor efficiency is 0.90% and the brake efficiency is 75%. The paddle tip velocity is 0.41 m/s. The temperature in the flocculation tank is 20°C. The total combined projected area of the paddles is 10.1 m . Determine the coefficient of drag.

6.37 The power input into a compartment of a flocculator is 0.21 kW. The motor efficiency is 0.90% and the brake efficiency is 75%. The paddle tip velocity is 0.41 m/s. The total combined projected area of the paddles is 19.1 m and the coefficient of drag is 1.6. What is the temperature at which the flocculator is operated?

6.38 The power input into a compartment of a flocculator is 0.37 kW. The motor efficiency is 0.90% and the brake efficiency is 75%. The paddle tip velocity is 0.41 m/s. The temperature in the flocculation tank is 20°C. The total combined projected area of the paddles is 10.1 m and the coefficient of drag is 1.64. What is the value of the constant a?

6.39 The power input into a compartment of a flocculator is 0.37 kW. The motor efficiency is 0.90% and the brake efficiency is 75%. The temperature in the flocculation tank is 20°C. The total combined projected area of the paddles is 10.1 m and the coefficient of drag is 1.64. What is the paddle tip velocity? 6.40 Repeat Example 6.7 assuming a CD value of 1.8. 