Electronic Material Properties - und Geowissenschaften ...

Groundwater treatment technologies
Christoph Schüth
Contamination of groundwater with organic contaminants, especially chlorinated
hydrocarbon compounds (CHCs) and petroleum hydrocarbons as constituents of
gasoline, is a wide-spread problem in industrialized countries. The treatment of the
contaminated groundwater is in
most cases achieved by
pumping it through an
adsorbent on-site, e.g. granular
activated carbon (GAC). The
efficiency of such a system can
be further increased by air
stripping the contaminants, as
the sorption capacities of these
compounds on GAC are
increased out of the gas-phase,
due to the minimization or
absence of competitive effects
of the groundwater itself or
other groundwater solutes.
Fig. 1: HFM module. The contaminated groundwater
enters the module at one side and flows over the
shellside (outside) of the hollow fibers to the outlet.
Nitrogen is used as an inert strip gas and is applied
on the lumenside (inside) of the hollow fibers in
counterflow.
Furthermore, alternative
destructive treatment options for the gas phase exist, e.g. catalytic oxidation, or
reductive catalysis especially for chlorinated compounds.
Packed tower aeration is the
most common stripping
method, although it has
several disadvantages. An
alternative approach is the
use of polypropylene hollow
1
100
fiber membrane modules
(HFM), that are routinely
used for the degassing of
process waters e.g. in the
electronics industry or for
0.1
50
the deaeration of bottled
beverages (Fig. 1). With a
very small footprint, these
units provide a large surface
area for mass transfer and
enable an independent
control of gas and liquid flow
rates without the risk of
flooding. Volume specific
overall mass transfer
coefficients for HFM
0.01
0
0.01 0.1 1
H (-)
Fig. 2: Removal efficiencies for the 12 compounds using
three
different experimental conditions (water flow rate
constant
tant at 0.4 l/min, gas flow and pressure combinations
of 2.0 l/min and 0.25 atm (open circles), 0.8 l/min and 0.1
atm (solid circles), 0.4 l/min and 0.05 atm (solid triangles)
respectively, resembling constant Ra/w ratios of 20, and
co rresponding mass balances (symbols with dotted lines).
stripping have been reported to be an order of magnitude higher compared to packed
C/C0 (-)
NAP
1,1,2,2-TCA
MTBE
- 141 -
1,2-DCA
1,2-DCB
1,4-DCB
CB
cis-1,2-DCE
TOL
TCE
PCE
1,1-DCE
Mass balance (%)