2. INTRODUCTION
• Oil-water separators are "in-line" devices used to remove
oils and greases (and sometimes solids) from industrial
waste streams and storm water discharges
• operate by employing various physical or chemical
separation methods, including gravity separation, filters,
coagulation/flocculation, and flotation
• use of any separation process depends on the properties
of the oil in the oil/water mixture
3. cont.
• There are many different design of oil-water separator. Each has different oil separation
capability and are used in different industries.
• Oil water separators are designed and selected after consideration of oil separation
performance parameters
• Oil water separators can be designed to treat a variety of contaminants in water including
free floating oil, emulsified oil, dissolved oil and suspended solids.
• Not all oil separator types are capable of separating all contaminants. The most common
performance parameters considered are:
– Oil droplet size (in the feed to the separator)
– Oil density
– Water viscosity (temperature)
– Discharge water quality desired
– Feed oil concentration and the range of oil concentrations likely
– Feed oil water flow (daily and peak hourly)
4. Parallel Plate Separator FLOW
PROCESS
• The beauty of the OWS design lay
within the simplicity. As shown in the
figure below the feed enters the OWS
on the left (for reference) and is
immediately directed downward. The
feed then flows upward through a
media pack. Inside the pack the de-
emulsified oil begins to coalesce and
float upwards and over a baffle into an
isolated oil collection chamber.
• The clean liquid that does not float is
decanted off the side over an adjustable
weir at a liquid level slightly lower than the
floating oil.
• Any solids that may enter with the feed
are separated early in the process and
collect in the sludge chambercoalesce:process by which two or more droplets,
bubbles or particles merge during contact to
form a single daughter droplet, bubble or particle
5. Stoke's Law
• relates the terminal settling or rise velocity of a smooth, rigid sphere in a viscous fluid of known
density and viscosity to the diameter of the sphere when subjected to a known force field
(gravity).
V = (2gr²)(d1-d2)/9µ
V = velocity of rise (cm sec-¹),
g = acceleration of gravity (cm sec-²),
r = "equivalent" radius of particle (cm),
dl = density of particle (g cm -³),
d2 = density of medium (g cm-³), and
µ = viscosity of medium (dyne sec cm-²).
