Environmental Science & Engineering - www.esemag.com - November 2004
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Oil/water separator tank installation for airport expansion
By Thomas Schoendorf
The expansion of Pennsylvania's
Susquehanna Area Regional
Authority's Capital City
Airport runways, taxiways, and
parking area made it necessary to
update the stormwater drainage system
to accommodate increased flow rates.
Buchart Horn, Inc., of York, Pennsylvania,
was lead design engineer for
the expansion project and upgrades to
the stormwater drainage system.
The engineers specified an
Oil/Water Separator system to satisfy
the Airport's National Pollutant Discharge
Elimination System (NPDES)
permit. The EPA requires facilities
that engage in regulated industrial
activities to obtain NPDES permits
before discharging to stormwater. The
Airport's de-icing and fueling facilities
are specifically identified as
industrial activities subject to the
NPDES regulations.
The engineers selected the
Highland Tank Model HTC-30,000 US
gallon "EZ Access" Oil/Water Separator
designed for the treatment of contaminated
stormwater runoff at 0-3000
gallons per minute discharging, with a
qualified/certified effluent quality of
10 ppm of free oil and
grease. These separators
meet the new Underwriter's
Laboratories,
Inc. SU2215 design,
construction, and performance
standards for
engineered Oil/Water
Separators rated at 10
ppm oil and grease.
Currently, code enforcement
officials consider
UL-SU2215 certification
as being the preeminent
national consensus
standard for oil/
water separator construction
and performance.
The separator is
designed for gravity
separation of free oils
(hydrocarbons and other
petroleum products)
along with some settleable solids from the wastewater.
The unit is designed with an
oil/water separation chamber containing
an inclined parallel plate coalescer
with removable, corrugated plates,
sloped toward the sediment chamber,
and built in accordance with API-421
sizing calculations. The parallel plates
direct the flow of the separated oils to
the surface of the tank and separated
solids to the bottom. A sectionalized
removable screen, polypropylene
impingement coalescer, designed to
intercept oil globules of 20 microns in
diameter or larger, is located at the
effluent end of the oil/water separator
tank for further treatment of the
wastewater.
Upstream of the oil/water separator,
the engineers specified an additional
Highland Tank treatment vessel with a
Model HT-DB 15000 gallon Interceptor
Tank. The double basin interceptor
is engineered to intercept and
collect sand, grit, grease and some free
oils before entering the primary treatment
tank. The primary function of the
Interceptor is to retrofit with the existing
30" concrete stormwater pipe at
the site. The double basin was
equipped with an Overflow Bypass to
direct the target treatment rate of 3,000 US GPM to the oil/water separator and
prevent overloading of the oil/water
separator in the event of a major storm.
Both vessels were built with Double
Wall Type-1 construction (360 degree)
steel secondary containment. The
inner steel tanks are completely contained
within the outer tanks and
equipped with a leak detection system.
The tanks were fabricated in strict
accordance with HighGuard™ Corrosion
Control System with a 30-year
warranty and meeting UL standards.
The HTC-30,000 gallon Oil/Water
Separator was supplied with a hi oil
level alarm (audio/visual) and an EZ
Access Manway design. The EZ
Access design utilizes large rectangular
manways located above the corrugated
plates and Petro-Screen™ allowing
personnel to inspect and maintain
the unit from grade level. Also the
large manways allow access to the
removable plates and screens.
Every effort has been made to
ensure that stormwater discharge from
the expanded facility will offer no
threat to water quality.
Thomas Schoendorf is with Highland
Tank & Mfg. Co.
Contact e-mail: tschoendorf@highlandtank.com.
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