ANAEROBIC PRETREATMENT OF CORN ETHANOL
PRODUCTION WASTEWATER
Jelte Lanting, Environmental Engineer
Biothane Corporation
Camden, New Jersey 08104
Robert L. Gross, Environmental Engineer
South Point Ethanol
South Point, Ohio 45680
INTRODUCTION
A five-month pilot study utilizing a six cubic meters Upflow Anaerobic Sludge Blanket Biothane
digester was recently performed on site of South Point Ethanol, a corn ethanol producer in Southern
Ohio.
The study was made to evaluate this type of pretreatment technology as a means of rectifying
compliance problems experienced with the facility's existing aerobic trickling filters. The focus of the
study was the COD and BOD purification efficiency which could be achieved at average volumetric
loadings near 10 Kg COD per cubic meter reactor volume per day and an evaluation of process
stability given the highly fluctuating nature of the wastewater characteristics.
THE BIOTHANE PROCESS
The Biothane process has evolved from research initiated by Lettinga and co-workers during the
seventies when interest in anaerobic digestion was revitalized as a result of the energy crisis. Major
strides in the development of the Upflow Sludge Blanket system in general were made at that time
in the Netherlands [1].
An important role in the development of the Biothane process in particular was played by CSM,
a Dutch beet sugar company [2]. Its efforts led to the development of a so-called three-phase separator
[3,4] and ultimately to a number of patent applications regarding the reactor design.
The key to success of a high rate anaerobic treatment process is its ability to maintain a high
solids retention time to compensate for the low sludge yield of anaerobic biomass. The Biothane
process achieves that goal by means of a patented three-phase separator, more commonly referred
to as a settler, located in the top of the reactor. The settler, when properly sized, allows for effective
degassing of biomass and encourages the development of a highly settleable, granular biomass. The
characteristics of these biomass granules allow reactors to be operated at average biomass concentrations of 20 to 40 Kg VSS per cubic meter reactor volume.
Recent experiences with Biothane pretreatment facilities for treatment of industrial wastewaters
in the United States have been described by Christensen [5] and Sax [6].
SOUTH POINT ETHANOL
South Point Ethanol is a corn to fuel grade ethanol facility producing 230,000 cubic meters of
denatured ethanol and 200 million kilograms of distillers dried grains with solubles (DDGS) each
year. Approximately 100 cubic meters per hour corn is pulverized, cooked, mixed with enzymes and
yeast, and added to one of eight large fermenters. The fermented corn slurry (beer) is pumped through
a series of columns to distill off the product ethanol. Residual corn is dried using centrifuges, dryers,
and evaporators prior to being sold as DDGS. This process operates 7 days per week, 330 days per
year with two scheduled maintenance outages.
The majority of process wastewater (90%) is generated in the evaporation and drying processes.
905