Air stripping tower

EXAMPLE 6.10 Air-Stripping tower with first-order degradation, modeled as plugfiow, plug flow with dispersion, and mixed tanks-in-series reactors... 

The air-stripping tower, illustrated in Figure E6.10.1, provides the air-water contact area, either through a porous medium that is unsaturated with water, through bubbles rising through the water or both. The polluted water comes in at the top (Co), and cleaner water comes out of the bottom of the stripping tower, while clean air comes in at the bottom, and air with trichloroethylene in it comes out the top of the tower. This... 

Table E6.10.1 Time response of the air-stripping tower output after a conservative tracer pulse input att = 0...

Now, we need a solution to the plug flow with dispersion model for steady-state operation of an air-stripping tower. The mass transport equation for this situation, assuming minimal trichloroethylene builds up in the bubble, is... 

When the effects of time variations in release rates are included, pulse (or instantaneous) and continuous (plume) emissions are the two most common time-variant inputs in transport models. The classic example of a pulse release is a hazardous waste spill. The steady release of contaminants into groundwater from a subsurface contaminant and the continuous release of volatile solvents from an air-stripping tower are examples of plume emissions. 

Fig. 9. Air stripping towers, (a) Packed tower (b) tray tower.

Air-stripping tower diameter is selected as a function of the liquid loading rates necessitated by the required design flow capability. The optimum tower diameter may be determined with the use of pressure-drop curves developed by Eckert (11) as shown in Fig. 3. The volumetric air-to-water ratio, calculated by Eq. (9), is converted to a weight-to-weight ratio and plotted on the abscissa in the form ... 

With progressive development of the computer technology, substanhal advancement has been made in the area of developing models to simplify the air-stripping tower design... 

The design of an air stripping tower is essentially similar to that of the conventional cooling tower (12). There are two basic types of tower configuration crosscurrent and countercurrent, with the former being more common at the present time. 

D. Hand, J. Crittenden, J. Gehin, and B. Lykins, Design and evaluation of an air-stripping tower for removing VOCs from groundwater. J. Am. Water Works Assc. 78(9), 87 (1986). 

J. C. Little and B. J. Marinas, Cross-flow versns counterflow air-stripping towers. J. Environ. Eng. -ASCE 123(7), 668 (1997). 

An air-stripping tower is to be designed to remove volatile organic compounds (VOCs) from water droplets. The overall mass transfer coefficient in the liquid phase is given by ... 

Stocking et al. identified two water supplies in the US which use air stripping as treatment technology. Inlet MTBE concentrations of 96 and 900 xg/L were removed to above 95% in both cases. The second installation had two air stripping towers operating in series with an air-to-water ration of 175 1. 

Li, L., Wang, H. W. Lu, J. H. 2006. Nitrogen removal using air stripping tower in inban wastewater treatment plant China water wastewater 22(17) 92-94. (Chinese with English abstract)... 

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