DESIGN AND OPERATION OF WET CORN MILLING PRETREATMENT
FACILITIES
L. M. Lace, Environmental Engineer
C. H. Huether, Environmental Engineering Manager
Daniel International
Greenville, South Carolina 29602
M. Tepoorten, Plant Chemist
The Canada Starch Company Inc.
Port Colborne, Ontario
Canada L3K 5X7
H. H. Trayner, Energy Environmental Superintendent
The Canada Starch Company, Ltd.
Cardinal, Ontario
Canada KOE 1EO
INTRODUCTION
Wet Corn Milling wastes are readily biodegradable in biological treatment systems; however, effluent limitations are difficult to attain due to high effluent suspended solids concentrations [1-3].
Additional complications are due to large fluctuations in influent BOD concentration due to variability of raw materials and production schedule [1,3]. The major characteristics of wet corn milling
wastewaters are poor settling characteristics and excessive filamentous organisms in the sludge
[2-5]. Pilot plant and lab scale operations have shown excellent results not substantiated by full scale
operations [4,5], although Bensing and Brown [2] achieved satisfactory sludge separation in a lagoon
system settling pond which is well suited to cold weather operation [6].
CASE HISTORY
Five months prior to process plant start-up of the Canada Starch Co. Inc. (CASCO), Port Colborne, Ontario, Wet Corn Milling plant, Canada Starch was notified by the Municipal Authorities
that the municipal wastewater treatment plant was unable to treat the plant wastewater as originally
permitted.
Pre-treatment requirements limiting discharge to 500 mg/I BOD and SS were imposed. In addition
there was substantial concern by the authorities that the impact of the high carbohydrate wastewater
on the municipal plant would cause an unacceptable decrease in effluent quality due to the increased
presence of filamentous organisms characteristic of the sludge.
Pretreatment Requirements
Expected wastewater quality and quantity were estimated on the basis of prior owner experience
at other wet corn milling plants. Plant wastewater was expected to be composed of sanitary, utility,
and process waste streams. Process wastewater originates from anion and cation exchanger backwashes, softener backwashes, steepwater condensate and plant cleaning. Discharge limitations were
determined by the regional authorities to be 500 mg/I BOD and SS. Expected plant raw wastewater
characteristics were as shown:
Flowrate
507,000 gpd    (1999 m'/d)
BOD
1,015 mg/1
SS
95 mg/I
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