TABLE OF CONTENTS Air stripping is a mass transfer operation in which a mass of volatile groundwater or wastewater constituents is transferred from the liquid phase (water) to the gas phase (air) and thereby removed from solution. Air stripping occurs in many biological treatment systems, not by design necessarily but by virtue of the aeration of the mixed liquor.
Volatile Organic Compounds (VOC) removal in wastewater is becoming an area of heightened interest due to increasingly stringent pretreatment and NPDES discharge limits for VOCs. However, many regulatory agencies will not allow stripping VOCs from wastewater with subsequent discharge to the atmosphere. Some require that stripped VOCs be captured and treated. Regulatory agencies increasingly require covering the equalization and aeration basins of treatment plants treating high levels of VOCs to prevent their release. Air stripping is used extensively to remove VOCs from contaminated groundwater.
The removal of volatile compounds by air stripping is dependent on the Henry's Law constant. Table 6.5 summarizes air stripping removal rates and Henry's Law constants (experimentally determined for 25 C) and solubility for selected compounds.
| Compound | Henry's Law Constant [*] (Dimensionless) | Solubility (mg/L) | Observed Removal (%) |
|---|---|---|---|
| Benzene | 0.23 | 1,780 | 90 |
| Carbon tetrachloride (tetrachloromethane) | 1.26 | 800 | 89 |
| Chlorobenzene | 0.16 | 448 | 97 |
| 1,1,1-Trichloroethane | 0.21 | 4,400 | 99 |
| Chloroform (trichloromethane) | 0.14 | 7,840 | 99 |
| 1,2-Dichlorobenzene | 0.081 | 100 | 93 |
| 1,3-Dichlorobenzene | 0.11 | 123 | 95 |
| 1,4-Dichlorobenzene | 0.11 | 79 | 97 |
| 1,2-Trans-dichloroethylene | 0.22 | 6,300 | 84 |
| 1,2-Dichloropropane | 0.123 | 2,700 | 98 |
| Ethylbenzene |
