41    EIGHT YEAR FULL-SCALE EXPERIENCE WITH
ANAEROBIC TREATMENT OF POTATO PROCESSING
EFFLUENT
Andre de Vegt, Manager of Technology
Paques, Inc.
Exton, PA 19341
Tom Vereijken, Senior Process Specialist
Paques B.V.
Balk, The Netherlands
INTRODUCTION
The potato processing company Fri-d'Or is located in Bergen op Zoom and Tilburg, The Netherlands. It produces french fries, instant mashed potatoes, and special potato products.
In 1982, the company installed a combined anaerobic/aerobic wastewater treatment plant in their
Bergen op Zoom facility in order to reduce the increasing city sewer surcharges. The anaerobic reactor
selected was of the Upflow Anaerobic Sludge Blanket Type (UASB). The UASB process was developed in the seventies by the group under professor Lettinga at the Agricultural University of
Wageningen, The Netherlands. The potato processing industry was one of the first industries where
this new process was introduced.
Early in the eighties, the UASB reactors were still designed on the basis of "flocculent" sludge. The
UASB at Fri-d'Or was designed for operation at a volumetric loading of only 4 kgCOD/m3.d. The
actual COD load however was twice as high as this design load, thereby causing problems in retaining
the flocculent sludge in the reactor. Regular addition of granular sludge from other reactors was
required to ensure that a sufficient amount of biomass was maintained in the reactor.
Over the course of several years, a lot more experience has been gained with highly loaded systems
on potato processing effluent. Application of this knowledge to the UASB at Fri-d'Or has led to a
very stable operation with excess granular sludge production. In this paper the general production
process of french fries production will be described with special attention to the various by-products/
waste streams. The history of the treatment plant will be described, focusing on the impact of process
modifications on the treatment results. Some recent operational data will also be presented and
discussed. Finally, it will be shown how an anaerobic treatment plant designed to treat potato processing effluent in 1991 differs from one designed in 1982.
POTATO PROCESSING PLANT DESCRIPTION
Fri-d'Or has operated a frozen pre-fried french fries production line since 1980 and an instant
mashed potato production line since 1983. Production is 24 hours per day, 5.5 days per week with a
total work force of 200 people.
A simplified process schematic of the french fries production line is shown in Figure I. The
schematic shows the different process steps and the different by-product and waste streams.
The instant mashed potato line contains the same washing and peeling steps as the french fries line
but the process steps after the peeling are different. The washed and peeled potato is cut in 10 mm
thick slices. After under water storage, the free sugars are rinsed off in a next washing step. This is
followed by a quick cooking step (to gelatinize the starch). After cooling, the slices are washed again
to remove the starch and sugars released from the potato cells in the cooking and cooling processes.
This is followed by steam cooking, mashing, drying, packaging and shipping.
The by-product and waste streams are almost identical for both lines. As a result of more process
steps and more washing in the mashed potato production line, the combined process water of both
production lines has a higher COD and suspended solids concentration than would have been the case
if only french fries were produced.
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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