25-05-2012, 02:15 PM
STORM WATER SOLUTIONS
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Design and Operation
Basic Operation
Conventional oil/water separators operate on the principal of gravity separation, using baffles or T-pipe
sections to retain free-floating oils. With their limited treatment capacities, they are only effective on oil
droplets greater than 150 microns. The VortClarex® system builds on this conventional oil/water
separator design by incorporating an innovative media designed to maximize the surface area
available for the coalescing of oil droplets. A typically sized VortClarex is capable of removing oil
droplets down to 60 microns.
The coalescing media or corrugated plates provide a surface onto which oil droplets coalesce. The
calcium filled polypropylene media attracts oily substances because of its affinity for hydrocarbons
(oleophilic). Oil droplets are then able to combine, forming larger droplets that rise to the surface more
quickly - increasing the separation rate and reducing hydrocarbon levels in the effluent. When properly
sized the VortClarex system will provide an effluent quality of 10 ppm (parts per million) or less for
most stormwater applications.
Flow enters the VortClarex system via a non-clog diffuser that distributes it across the chamber width.
The influent passes over a solids baffle wall where settleable solids drop out, reducing the amount of
solids in the flow as it enters the coalescing media. As the flow passes through the media, oil droplets
accumulate on the surface and come into contact with others to form larger, more buoyant droplets.
These larger droplets rise upward through the media and are released near the water surface. The oil
is trapped behind the outlet T-pipe, and treated water exits the system.
Design Process
Stoke’s Law
Gravity separation occurs due to the difference in specific gravity between oil and water. The rate of
this separation is calculated using a formula known as Stoke's Law. The formula predicts how fast an
oil droplet will rise through water based on the droplet density, size and distance it must travel.
Coalescing media improves the efficiency of oil/water separators by reducing the distance oil droplets
need to rise before joining other oil droplets and rising to the surface. Once the oil comes in contact
with the media, the oleophilic polypropylene material effectively removes it from the flow stream. Oil
accumulates on the media surface, forming larger and more buoyant droplets that eventually break
away from the media, rise to the water surface, and are trapped and isolated from the system outlet.
Maintenance
Inspection
The VortClarex system should be checked periodically to determine if excessive amounts of solids
and/or oils have accumulated. Solids accumulation in the lower sections of the VortClarex coalescing
media will reduce oil removal efficiencies. Regular inspection and maintenance will eliminate any
compromise in performance due to solids build-up.
After the first six (6) months of operation, the inlet area should be inspected and cleaned as follows:
1. Remove separator cover.
2. Dispose of separated oil per regulatory procedures.
3. Remove water from separator.
4. Clean the vault by flushing with a hose and examine the plates for blockage.
5. Remove accumulated sediment with a vacuum truck or positive displacement pump such as
an air operated diaphragm pump. The sediment will contain hydrocarbons so proper disposal
is required.
Note: Measure and record the depth of the solids in the inlet chamber. If
sediment level is 6 inches or more, the cleaning interval should be
shortened. If the sediment is less than 6 inches deep, the interval can be
increased.
Cleaning
The VortClarex coalescing media can be cleaned either while in the system or after removal from the
system.
Cleaning in place
1. Using a water hose, direct spray (10-15 psi) into plate spacing on top of the plate packs.
2. Using a vacuum suction hose, remove any sediment or oily contaminants that are flushed out
of the coalescing media.
Cleaning after removal
1. Pump all water and oily contaminants from the VortClarex system.
2. Remove coalescing media.
3. Place media on an impervious surface lined with 6 mil plastic sheeting surrounded by a berm
to prevent discharge of contaminated water into surface or groundwater.
4. Flush media with water hose (10-15 psi) to remove heavy oil coating or sludge from between
the corrugated plates.
5. Examine tank interior for damage and repair any damage to internal coating.
6. Re-Install plate packs one at a time, one row in length and one row in width, being sure the
outer packs are adequately sealed against the vault wall in the same manner as before they
were removed.
7. After all packs are installed, check to ensure that the packs are even and touching, forming
one (or two if provided) rows of packs across the channel and that they are securely butted
against the backing angle at the bottom of the separator. Install the upper channel to ensure
the plates are secured in place.
8. Secure hold down channel ensuring it is snugly in place.
9. Check to see that there is no possibility of fluid bypassing around the plates and the side wall
of the vault, as well as between plate pack assemblies, since this could adversely affect the
efficiency of the separator.