|
Oil
Recycling Facility Wastewater Treatment
System
Process Description
Oil Recycling Facility wastewater comes from
the recovered water and equipment cleaning operations in an oil
recycling facility. The wastewater is generated when processing of
the oil yields a recovered water that is loaded with emulsified oil
and various other hydrocarbons.
Oil Recycling Facility wastewater is treated
by adjusting pH downward (or upward) using acid (or caustic) and
using a strong coagulant chemistry to break emulsions caused the oil
recovery process. The pH is then raised to ~8.5 with a coagulant
added to precipitate and coagulate oil and solids. A flocculent is
then used to increase particle size and assist in separation.
The typical method to treat Oil Recycling
Facility wastewater is as follows:
Stage 1 Emulsion Cracking/pH Adjustment:
pH is lowered (or raised) to ~3.5 with the pH controller using acid
(or caustic). A coagulant de-emulsifier is added to break any
emulsion.
Stage 2 pH Adjustment/Precipitation and Coagulation:
pH is adjusted to ~8.5 using caustic and a coagulant is added such
as Alum or PAC to cause further de-emulsification and precipitation
of the solids. A “pin floc” is developed indicating the emulsion and
the suspended solids are precipitated.
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 floc into larger particles suitable to be enmeshed with the air
bubbles.
Clarifier, Dissolved Air Flotation (DAF):
The flocculated wastewater is introduced into the DAF inlet where
the floc particles are comingled with a pressurized dissolved fine
bubble recycle stream. The floc particles attach to the bubbles and
float to the surface where they are mechanically skimmed into the
float scum sludge chamber. The clarified treated water then exits
the end of the DAF and flows downstream to sewer or further
treatment if necessary. The DAF system bubbles come from a Recycle
Air Dissolving system that takes a portion of treated effluent,
pressurizes it and introduces air to be dissolved. The dissolved
air comes out of solution and forms a fine bubble stream when the
pressure is released at the DAF entrance in the presence of floc
wastewater.
DAF
Sludge Handling:
The resulting DAF waste scum/sludge is removed from the DAF
automatically as the scum accumulates and is pumped to the sludge
holding tank where it further thickens and accumulates a batch for
disposal or processing in a filter press. The sludge is mixed and
conditioned with a filter aid such as DE to improve porosity and
filterability.
Sludge Dewatering:
The thickened DAF scum/sludge is allowed to accumulate sufficiently
to provide a full batch for the Filter Press. First a precoat
slurry is circulated thru the filter press to coat the cloths with
DE to prevent blinding of the cloth and aid in easy cake removal.
The filter press is then pumped with sludge until it is full. The
press is emptied of the “cake” which is a semi solid of
approximately 20-35 % solids. Sludge cake is high in fats and
greases and solids and should be disposed of according to
environmental regulations.
APPLICATIONS:
|
