Section Seven
OIL AND GREASE WASTES
18    REMOVAL OF OIL AND GREASE IN THE HYDROCARBON
PROCESSING INDUSTRY
Choong Hee Rhee, Senior Engineer
Paul C. Martyn, Supervising Civil Engineer
Jay G. Kremer, Head, Industrial Waste Section
Sanitation Districts of Los Angeles County
Whittier, California 90607
INTRODUCTION
The hydrocarbon processing industry in the Sanitation Districts of Los Angeles County's (Districts)
service area includes petroleum refining, petrochemical processing, crude oil and natural gas production, and related chemical companies. The volume of wastewater discharged from the hydrocarbon
processing industry is approximately 23 MGD which is about 35% of the Districts' total industrial
wastewater flow and 6% of the 365 MGD of wastewater influent to the Districts' Joint Water
Pollution Control Plant (JWPCP). Crude oil capacities of petroleum refineries total nearly one
million barrels per day.
The most important pollutants in the hydrocarbon processing industry are conventional pollutants
such as oil and grease, suspended solids and pH, and nonconventional pollutants such as phenolic
compounds; COD, sulfide and ammonia. Among these pollutants, oil and grease is one of the most
complicated pollutants to remove. Should there be excessive discharges of oil and grease, receiving
sewerage systems may experience problems with clogging of sewers and pumping plants from the
precipitation of oily solids, fire hazards, interference with biological treatment process and complaints from offensive petroleum odors. This paper summarizes available technologies to remove oil
and grease and should assist oil and grease dischargers in complying with their effluent limits.
THE COMPOSITION OF HYDROCARBONS
Hydrocarbons exist in the liquid, solid or gaseous state, generally depending on the number and
arrangement of the carbon atoms in their molecules. At normal temperatures and pressures, those
hydrocarbon molecules with up to four carbons are gaseous, those with twenty or more carbons are
solid and those in between are liquid (such as crude oils).
The simplest hydrocarbon is methane, it is comprised of one carbon atom surrounded by four
hydrogen atoms. The larger hydrocarbon molecules have two or more carbon atoms joined to one
another as well as to hydrogen atoms.1 The carbon atoms may link together in a straight chain, a
branched chain or a ring. The simpler hydrocarbons found in crude oils are paraffins (saturated
hydrocarbon) in which each carbon atom is linked with the maximum possible number of hydrogen
atoms with the generic formula of CnH2n + 2- Hydrocarbons with straight or branched carbon atom
chains and containing less than the maximum of hydrogen atoms per carbon atom are called "unsaturated" or "olefinic" and have the generic formula of CnH2n. Examples of these types are shown in
Figure 1.2 Petroleum crude oils contain hundreds of different hydrocarbons, some of which are as
complex as C^H^.
TEST METHODS FOR OIL AND GREASE
The test procedures used to measure oil and grease concentrations in wastewater do not determine
the presence of specific substances, but groups of substances that can be extracted from a sample
using a particular solvent. The sixteenth edition of Standard Methods for the Examination of Water
and Wastewater) provides for the use of three test procedures to determine oil and grease concentra-
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