PERFORMANCE OF A POTATO PROCESSING
WASTEWATER TREATMENT PLANT
A CASE HISTORY
T. Viraraghavan, Associate Professor
Faculty of Engineering
University of Regina
Regina, Saskatchewan
Canada S4S OA2
R. C. Landine, Senior Environmental Engineer
A. A. Cocci, Senior Environmental Engineer
ADI Limited
Fredericton, New Brunswick
Canada E3B 4Y2
INTRODUCTION
A large potato processing plant in eastern Canada became operational in the spring of 1971. The
main product is french fried potatoes, but instant potato flakes are also manufactured, and there is a
starch recovery plant. A new byproduct line went into operation in the spring of 1979. A new pizza
plant also discharges wastes to the wastewater treatment plant.
The wastewater treatment plant is comprised of several unit operations, viz., screening, primary
settling, two-stage trickling filtration, and secondary settling. Primary sludge is dewatered in a
vacuum filter and the dewatered sludge is hauled away. The secondary sludge is usually pumped to a
digester and dewatering lagoon. Details of the treatment plant are available elsewhere [1].
ADI Limited, consultants to the processing company, conducted a comprehensive survey of the
wastewater treatment plant in April, 1976, and found that unit pollution loadings had tended to
increase and BOD removals across the primary clarifier and the biofilters were not steady; sometimes
they were poor. It was then recommended that recirculation be maintained on the trickling filters
when BOD of the influent to the filter exceeded 500 mg/l and that a 24 h sampling program should be
set up.
ADI Limited carried out a study in 1979 essentially to assess the impact of the new byproduct line
on the treatment plant. This study revealed that: (1) the average flow to the treatment plant had
increased; (2) the byproduct line was contributing significantly to the total hydraulic and organic load;
(3) the effluent BOD limit was not met due to poor performance of the secondary system; (4) the poor
performance of the secondary system was due to improper distribution of wastewater to the top of the
filter media and oxygen deficiency; and (5) that an upgrading program was required to handle the expected design load. It was recommended that forced draft ventilation of trickling filters be carried out
and pretreatment prior to trickling filtration be given due consideration in treatment plant upgrading.
The company decided to carry out several of the proposed modifications to the treatment plant and in
plant changes and study the impact of these changes in 1980 after the expected conversion to steam
peeling in the fall of 1979. Analysis of plant performance in 1980 showed that its efficiency was
substantially improved in comparison with 1979 performance and met effluent limits; the pollution
load projections became 60% of the earlier figure: based on 1980 data.
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