After the undesirable portions of the used oil have moved into the water layer, the water layer and sludge can be removed by gravity settling, centrifugation, or pressure filtration, depending upon their physical state after treatment.
(the undesirable portions of the used oil; have moved; into the water layer) (the water layer and sludge; can be removed; by gravity settling, centrifugation, or pressure filtration; T:After the undesirable portions of the used oil have moved into the water layer)
the undesirable portions of the used oil the water layer and sludge
have moved can be removed
into the water layer
by gravity settling, centrifugation, or pressure filtration T:After the undesirable portions of the used oil have moved into the water layer