|
Groundwater Remediation Wastewater Treatment
System
Process Description
Contamination of
ground waters has occurred at many locations due to factors such as
leaking underground storage tanks LUST Sites) and improper chemical disposal practices.
Often, the major contaminants are petroleum hydrocarbons such as
gasoline, jet fuel, or VOC’s (volatile organic compounds) such as
BTEX (BTEX is an acronym for benzene, toluene, ethylbenzene, and
xylene. This group of volatile organic compounds (VOCs) is found in
petroleum hydrocarbons, such as gasoline, and other common
environmental contaminants).
The ground water
remediation process is designed to prevent the further spread of the
contamination and to remove the volatile contaminants. Extraction
wells are drilled around the perimeter of the contamination zone and
the water is pumped out for pressing through an air stripper.
After
remediation, the purified water may be pumped back into the ground
utilizing injection wells. These wells are located such that the
injected water forces the contaminated water toward the extraction
wells.
The typical method to reduce and remove
soluble electroplating metals from wastewater is as follows:
Stage 1– Precipitation and Coagulation:
pH is raised from ~3 to 8.5 with the pH controller using caustic
while adding a coagulant such as ferric chloride. Testing of the
wastewater may confirm that a coagulant is not needed. A “pin floc”
is developed indicating the metal is insoluble. Some applications
have plating enhancing chemicals present, emulsifiers and such that
may require more sophisticated high performance coagulants to break
the bonds and allow the metal to precipitate.
Stage 2 - Flash Mix:
The wastewater with it’s precipitated pin floc is introduced to the
flash mix zone where a polymer flocculent is added. This stage
maximizes flocculent dispersion throughout the coagulated
wastewater.
Stage 3 - Flocculation:
The wastewater is now introduced to the slow mix zone to agglomerate
the pin floc into larger rapid settling particles.
Clarifier, Inclined Plate:
The flocculated wastewater is introduced into the clarifier where
the settling particles land on the inclined plates and are directed
downward and into the sludge chamber. The clarified treated water
then exits the top of the clarifier and flows downstream to sewer or
further treatment if necessary.
Clarifier Sludge Handling:
The resulting clarifier waste sludge is periodically removed from
the clarifier at a slow rate and sent to the sludge holding tank
where it further thickens and accumulates a batch for disposal or
processing in a filter press.
Sludge Dewatering:
The thickened clarifier sludge is allowed to accumulate sufficiently
to provide a full batch for the Filter Press. The filter press is
pumped full of the sludge until it is full. The filter press is
then emptied of the “cake” which is a semi solid of approximately
20-35 % solids. Sludge cake is high in phosphate and should be
disposed of according to environmental regulations.
Air stripping is
used for removal of VOC’s and petroleum hydrocarbons on small
packaged systems. To
prevent fouling of the air stripping column, iron in solution must
be removed prior to the stripper.
Iron may be
removed by converting the soluble iron to the hydroxide form or by
oxidizing to ferric oxide. Although the sludge produced in either
case can be dewatered in a filter press, the oxide form is easier to
dewater than the hydroxide form. A small amount of bodyfeed or
other conditioning chemicals may be required to produce acceptable
filter cakes.
APPLICATIONS:
Ground Water
Remediation Sites |
