Table 1. Concentration, solubility and Henry's law constants of primary contaminants in
source water for medium temperature air stripping experiments.
Water
Henry's law
constants at 20C
Concentration
solubility*
(g/L)
(g/L)
(dimensionless)†
Compound
Trichloroethylene
34,000.000
1,100,000.0
0.378*
Tetrachloroethylene
15,200.000
150,000.0
0.59**
Methylene chloride
1,550.000
20,000,000.0
0.084*
0.315*
1,2-dichloroethylene
149.000
3,500,000.0
Chloroform
22.600
8,200,000.0
0.119*
1,990,000.000††
Total petroleum hydrocarbons
N/A
N/A
Napthalene
not directly analyzed
31,700,000.0
0.048*
Specific gravity at 1525C = 0.85*
No. 2 diesel fuel
not directly analyzed
* U.S. EPA (1990)
mg m 3
†
mg m 3
** Munz and Roberts ( 1979)
†† Two-phase sample concentration; soluble TPH concentration = 8450 g/L
less-steel trays, whereas in a packed tower they
Research goals
can precipitate on the packing, causing fouling
The research described in this report sought to
and short circuiting. Similarly, long-chain hydro-
evaluate the potential for transferring VOCs and
carbons tend to sorb to solid surfaces, potentially
long-chain petroleum hydrocarbons from a con-
fouling packed tower media. The vigorous bub-
taminated water to the vapor phase using a tray-
bling action in a tray-type stripper scours the unit's
type air stripper. The goal was to achieve high
interior during operation, usually limiting pre-
contaminant removal rates as economically as pos-
cipitation and biofilm development (Lamarre
sible, using only moderate liquid temperatures and
1993).
simple, commercially available equipment. The
tray-type air stripper used is known as Shallow-
Tray (North East Environmental Products, Inc.,
Research background
This research grew out of the need to remove a
West Lebanon, N.H.). A ShallowTray unit was cho-
variety of VOCs and diesel-range hydrocarbons
sen because of its resistance to fouling and low-
from approximately 30,000 L (8000 gal.) of water
profile size (approx. height, 2.12 m). The unit was
at CRREL. This was contained in an ice drilling
operated inside a large shed, allowing constant
test facility (IDTF) for approximately 20 years.
temperature control of the treatment process.
The IDTF is no longer used and is essentially an
The specific goals were to:
open-head storage for this contaminated water.
1. Measure and analyze the treatment perfor-
GC/MS analysis of individual contaminants in-
mance of concurrently stripping VOCs and petro-
dicated that the contaminants had been moder-
leum hydrocarbons from water by ShallowTray
ately weathered. Consequently, the contaminated
aeration as a function of liquid temperature and
water source provided an excellent opportunity
flow rate.
for a realistic treatment study using a homoge-
2. Measure and analyze the operating costs of
neous, weathered mix of dense and light aqueous
this treatment.
contaminants which was relatively free of par-
3. Using empirical data, derive formulas that
ticulate and biological interferences. The primary
could predict ShallowTray stripping efficiency as
contaminants in the water source and their criti-
a function of liquid temperature and flow rate,
cal properties are listed in Table 1. Under a Coop-
and as a function of power consumption per vol-
erative Research and Development Agreement
ume of water treated.
between CRREL and a local business (North East
4. Recommend the suitability of this process to
Environmental Products, Inc.), a commercial, tray-
remediate similar contamination sources.
type air stripper was made available for treating
Stripping performance was measured by de-
this contaminated water.
termining the influent and effluent concentrations
3
Previous Page
