CUSTOM DESIGNS CUT EFFLUENT TREATMENT COSTS
CASE HISTORIES AT CHEVRON U.S.A., INC.
B. T. Davies, Senioi Engineering Associate
R. W. Vose, Senior Engineering Associate
Chevron Research Company
Richmond, California 94802
INTRODUCTION
In designing a petroleum refinery effluent system, the basic Chevron design philosophy
is to be flexible.   Rather than adopting a rigid "cookie cutter" approach using a standard
conventional wastewater treating sequence, we develop a custom design using various
proven wastewater treating steps in a combination which best suits the particular situation.
In each case, we try to find the "best" system taking into account:   investment and operating cost; performance and reliability; flexibility and ease of operation; and integration
of existing facilities.
In this paper, we review the various processing steps for refinery effluent treating,
application of our design philosophy to various Chevron U.S.A. refineries, and preliminary
performance data for these systems.
There are two principal considerations in refinery effluent treating:   (a) the end-of-pipe
effluent system, and (b) effluent control at the source inside the refinery.   End-of-pipe
treatment is what we will discuss here.   Source control in the refinery, e.g., changes in
process operation or configuration to reduce wastewater flow or contamination, can achieve
substantial savings in end-of-pipe treatment; but it is a broad topic beyond the scope of
this paper.
BASIC STEPS IN REFINERY
EFFLUENT TREATMENT
Figure 1 shows a conceptual refinery effluent treating system.   It incorporates the following basic treatment steps:
1. Oil Separation
a. Primary (gravity) deoiling
b. Secondary deoiling
2. Biological Treatment (includes equalization and various types of biotreaters)
3. Final Suspended Solids Removal
Ancillary steps (e.g., storm surge capacity, sour water and spent caustic handling, reaeration to restore dissolved oxygen) may also be required.   pH control may be incorporated in Steps 1 and 2 according to need.
A choice of processes is available for each basic treatment step. We will review some
well known processes and discuss our experience and design preferences. In general, we
have attempted to develop design practices that are simple but adequate.
OIL SEPARATION
We usually consider two-stage deoiling.   Primary (gravity) separators to remove non-
emulsified, settleable oil, and secondary oil separators to remove emulsified oil.
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