| ACQUA
designed, installed and commissioned a groundwater treatment system
to remove hydrocarbons. Since the site was to be redeveloped for residential
purposes, the complete removal of dissolved phase hydrocarbons from
the aquifer level was of paramount importance. The groundwater decontamination
process involved placing spear points around the site according to
the land topography and where pockets of contaminated groundwater
lie. The IT Group was
required to deliver groundwater to the treatment system. ACQUA was
responsible for undertaking the processing of the groundwater, in
addition to ensuring the discharge of clean water from the site
to sewer. ACQUA designed a system that utilizes an IC-SEP*, an OWS
VGS* and a series of carbon filters. The complete system is capable
of treating 3,000 liters per hour.
The contaminated groundwater
is pumped to a preliminary holding tank capable of storing 3,600
liters of effluent. A floating skimmer removes free and floating
hydrocarbons to the VGS*. Within the VGS*, a pure hydrocarbon phase
is separated from the water and directed into a vessel for containment
and disposal. Water containing the remaining dissolved phase hydrocarbons
is pumped to the IC-SEP* system.
This oil/water mixture is mixed
with a dissolved air stream from the IC-SEP* unit. Separation of
the oil phase from the water phase occurs in the flotation tank
where the dissolved air comes out of solution and rises slowly to
the surface collecting the hydrocarbons and bringing them to the
surface for removal. A floating skimmer removes these floating hydrocarbons
with some of the water from the top of the flotation tank, and this
stream is also pumped to the OWS VGS*.
Treated water from the IC-SEP*
system is finally passed through two carbon adsorption columns where
remaining hydrocarbons are removed. This is the final polishing
step before the clean water is stored in a final holding tank for
testing prior to eventual discharge to sewer.
A vapour removal system is installed
in each of the tanks and pulls out any volatiles given off in the
process. These volatiles are removed in a carbon adsorption canister.
All of the equipment is located in a hazardous area and the appropriate
measures were taken to eliminate any source of explosion. Under
these circumstance, particular attention was paid to classification
of areas and the design of electrical panels.
Performance data for the ground
remediation process is shown below:
| |
Groundwater
Inlet |
Post
VGS* |
Post
IC-SEP* |
Post
Carbon Filter |
| |
µg/L |
µg/L |
µg/L |
µg/L |
| Benzene |
0.54 |
0.44 |
0.053 |
<0.001 |
| Ethylbenzene |
0.053 |
0.074 |
0.004 |
<0.001 |
| Toluene |
3.1 |
1.6 |
<0.010 |
<0.001 |
| Xylene |
31 |
3.6 |
0.003 |
<0.001 |
| TPH
c6-c9 |
280 |
15 |
2.7 |
<0.05 |
| TPH
c10-c |
240 |
23 |
6.3 |
0.48 |
| TPH
c15-c28 |
240 |
25 |
5.0 |
0.1 |
| TPH
c29-c36 |
2.4 |
0.3 |
0.1 |
<0.1 |
|
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