MIL-HDBK-1005/9A
These molecules react with emulsified oils or colloidal
material and form large floc particles. Sodium chloride (NaCl)
is not recommended for "salting out" emulsions since it is slow,
requires large amounts of NaCl (20 to 70 g/L), and results in a
corrosive liquid product. For chemical handling and feeding
details, refer to Section 4. General guidelines for the
selection and application of chemicals is as follows:
a) Coagulants. Anionic and cationic surface-active
agents are not compatible and tend to neutralize each other.
Generally, reactive anions such as OH- and PO4-2 will break water-
break oil-in-water emulsions. For oily wastewaters containing
dissolved iron, addition of an inorganic coagulant may not be
needed. This dissolved iron can function as a coagulant under
alkaline pH conditions. An inorganic coagulant in combination
with organic polymers can provide satisfactory demulsification
for oily wastewater.
b) Operating pH. Chemical addition to form a heavy
metal hydroxide flocculent precipitate can be used to break
dilute oil-in-water emulsions. However, the best emulsion
breakage effect by ferric chloride, ferric sulfate, and other
salts is achieved in an acidic medium. Limited application
exists at plants employing heavy metal or sulfide removal by
precipitation, as slightly alkaline conditions are desired for
these situations.
c) Wetting Agents. Wetting agents can break water-in-
oil emulsions. However, correct dosage is critical, as
overdosing will destroy the emulsion breaking action. Almost all
organic polymer formulations contain wetting agents and therefore
separate addition of these is not required.
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