88    CASE HISTORY: DEVELOPMENT OF A DEDICATED
SLUDGE APPLICATION SITE BY AMOCO CHEMICALS
CO. AND THE ASSOCIATED PERMIT TO OPERATE BY
SOUTH CAROLINA DEPARTMENT OF HEALTH AND
ENVIRONMENTAL CONTROL
Marie H. Bush way, Environmental Engineer Associate III
Division of Industrial and Agricultural Wastewater
South Carolina Bureau of Health and Environmental Control
Columbia, South Carolina 29201
Geoffrey L. Gilman, Senior Chemical Engineer
Amoco Chemicals Company
Cooper River Plant
Mt. Pleasant, South Carolina 29464
INTRODUCTION
Completed in 1978, the Cooper River Plant, located northeast of Charleston, SC, is the newest of
the five major domestic manufacturing facilities owned by Amoco Chemicals Company. With annual
shipments in excess of 1.3 billion pounds, the Cooper River Plant is the world's largest producer of
purified terephthalic acid, a chemical intermediate used primarily in the manufacture of polyester
fibers, films and molded plastics. Crude terephthalic acid is produced by the catalyzed air oxidation
of paraxylene and then purified by a proprietary hydrogenation process.
BACKGROUND
Amoco Waste Treatment Plant
The manufacturing processes, along with the Utilities Unit, produce about 1.5 million gallons per
day of wastewater normally containing 2500 mg/L of total organic carbon or TOC. The wastewater is
processed on-site through a conventional waste activated sludge treatment plant. The Waste Treatment Unit consists of two parallel biological oxidation (biox) trains each having three aeration basins
in series. Wastewater feed and recycled mixed liquor are introduced into the first and second stage
basins only. Each first stage basin contains eight low speed mechanical aerators, each second stage
basin, eight high speed aerators, and each third stage basin, five high speed aerators.
The biox trains are preceded by a primary basin with a six day retention time. In addition to
providing equalization, the primary basin acts as a clarifier to allow suspended solids to settle from
the wastewater reducing the waste feed concentration to less than 50 mg/L suspended solids. The
settled solids are sold as boiler fuel.
Each biox train is followed by its own secondary clarifier. The overflow is passed through a
polishing pond with a ten day retention time and a multi-media filter prior to discharge to the Cooper
River. The underflow is recycled at a one-to-one ratio with the feed. A side stream of the underflow is
wasted to one of two anaerobic lagoons to maintain the proper sludge age.
The wasted sludge digests in the anaerobic lagoons and is then pumped to a holding basin prior to
land application. The supernate is returned to the biox trains as a nutrient source. Anaerobic digestion
retention time is about four months with an additional two month storage capacity in the holding
basin. The total digestion process reduces total suspended solids by 30% and produces a sludge with
an average concentration of two percent total solids.
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