Ozone (O₃) dissolved in water is used in many wastewater treatment applications. Pure, 100% ozone gas at 1.0 atm and 20°C is continuously bubbled into a tank of liquid water. The rising bubbles keeps the liquid well mixed. There is no inflow or outflow of water. Initially, there is no dissolved O₃ in the water, but as time goes on, the dissolved O₃ concentration increases. The total volume of liquid in the tank is 2.0 m³. At equilibrium, the dissolution of O₃ in water at 20°C follows Henry’s law with H ˆ 0.070 atm m³/gmole.

a. It is desired to achieve a dissolved O₃ concentration of 4.0 gmole/m³ within 10.0 min of bubbling time. What is the required k_La for O₃ need to meet this constraint?

b. For your result in part (a), propose a suitable bubble diameter if the gas holdup is maintained at 0.005m³ gas/m³ liquid.

c. To change k_La, one could change the bubble diameter, aeration rate, and liquid viscosity. Describe how each variable would need to be changed (i.e. increase, decrease) in order to increase k_La.