76    PILOT TESTING AND DESIGN OF AN ACTIVATED SLUDGE
SYSTEM FOR REFINERY WASTEWATER
Edward C. Copeland, Senior Project Engineer
James D. Cole, Senior Project Manager
Heritage Remediation/Engineering, Inc.
Indianapolis, Indiana 46251
INTRODUCTION
In 1989, a small Midwestern refinery determined that its existing lagoon-based wastewater treatment system was incapable of consistently complying with the requirements of its anticipated NPDES
permit renewal. In addition, proposed stringent water quality standards, and other factors had made
it clear that either an upgrade or replacement of the existing wastewater treatment system was
required. This paper describes the investigation undertaken to determine the most effective system to
treat the refinery wastewater, in terms of both cost and performance. The operations performed by
the refinery put it in the Topping Subcategory for purposes of USEPA effluent guidelines limitations
(40 CFR Part 419)'.
WASTEWATER SOURCES
The refinery process operations generate the following wastestreams. The volatilized material from
the preflash, crude tower, quench stack, and stabilizer all contain a mixture of water and product in
vapor form. As this vapor is condensed, product separates from the water and is returned to the
process. The wastewater is split into two streams, one of which is discharged directly to the wastewater
treatment system. The remainder is diverted to the desalter. The desalter mixes oil and water intimately to remove dissolved salts and other inorganics from the oil. Water is removed by phase
separation and split, with part of it being recycled to the head of the desalter, while the remainder is
discharged to the wastewater treatment system.
The vacuum fractionation process is an additional source of wastewater. A mix of petroleum
fractions and condensed steam is discharged to the "hot well", then to an oil water separator. The
effluent from the separator passes through a cooling tower and is recycled to the vacuum process.
There is a periodic blowdown from this operation to the wastewater treatment system.
In addition to these process sources, there exist numerous non-process sources of wastewater to the
treatment system. Various sample ports on tanks and miscellaneous lines drain directly into the
process sewers. Of particular concern are the tank water draws from the caustic treater and merox
unit, where pure product such as jet fuel could be released directly into the sewer. Water drawn from
remote tanks is hauled via portable tanker and discharged directly to the front end of the treatment
system. Also, backwashes from the process water supply ion exchange system and the rock filter units
are discharged to the wastewater treatment system. Finally, stormwater runoff from the refinery unit
operations area, as well as water from the various tank farm diked areas, are diverted through the
process wastewater treatment system. It should also be noted that sanitary wastes are discharged to an
on-site septic system, not to the wastewater treatment system.
EXISTING WASTEWATER TREATMENT SYSTEMS
Noncontact cooling water is currently discharged directly through two outfalls, Outfall 002 and
Outfall 003. Both Outfalls discharge to a lake.
In the process wastewater treatment system, process water and part of the stormwater flow into a
two-train, in-series, API separator system (Figure 1). The wastewater is pretreated with a polymer to
improve phase and gravity separation. The initial API separator, the North API, is 15 feet wide by 47
feet long by 5 feet deep, and is divided into three sections by concrete "under and over" baffle walls.
Oil skimming is conducted manually in all three sections. Sludge removal is conducted biannually,
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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