| To disinfect (waste)water with ozone, ozone must be dissolved in water. Ozone gas is produced on-site by an ozone generator. It can be dissolved in water in various ways. |
To bring about a proper disinfection and oxidation, the ozone concentration must be as high as possible. The prediction of ozone solubility is more complicated than for other gasses, because ozone solubility is influenced by several factors, such as temperature, pH and dissolved matter. This is a consequence of the instability of ozone in water. The solubility of a gas in water is usually defined by Henry's law. For the solubility of ozone the Bunsen (β) and particularly the solubility ratio (S) factor is used.
Henry's law states that the solubility of a gas in a liquid is proportional to the pressure of the gas over the liquid. Principally, Henry's law can only be applied on gasses that do not chemically change in water, during transfer.
Y = HX
Y = pressure of substance over fluid [atm]
Figure 1: effect of pressure and feed gas concentration on ozone solubility
Henry coefficient (Hc)
H = Henry (atm/l/mol)
Figure 2 illustrates the solubility ratio (S) at increasing temperature, carried out by different researchers. The solubility is studied at different ion concentrations (μ). This figure illustrates that the solubility of ozone is influenced by several factors in the water.
Figure 2: ozone solubility (S) as a function of the temperature (T = 5-35 ˚C)
The following formula can be used to calculate of the solubility ratio (S) at different temperatures:
Figure 3: model for ozone transfer
The transfer rate is dependant on :
Figure 4: counter- and equal-flow contact column
In case of a venturi system, the ozone gas is dissolved in water by pressure. Pressure creates a constriction in the fluid flow, causing sucktion of ozone (figure 5). A venturi system has various benefits, namely: compact installation, no moving particles, high yield.
Figure 5: venturi system