Design of a Treatment Plant
for Bakery Wastes
C. S. GROVE, JR., Professor
DWIGHT B. EMERSON, Research Assistant
Department  of Civil  Engineering
Syracuse  University
Syracuse,   New   York
E.  F.  DUL,  Engineer
H. SCHLESINGER, Manager
Air-Water Pollution Control Division
W. BROWN, Project Manager
Advanced Planning Division
Lockwood Greene Engineers, Inc.
New York, New York
INTRODUCTION
General Description of the Baking Process and the Wastes Produced
Wastes produced in sweet-goods or pastry baking processes come from two
general sources. One source is from the baking pans which have to be washed after
each baking to remove grease, flour, sugar, and other materials which have remained.
The other major waste source is from washing fruit, milk and other containers and
from "scrub-down" operations. Once the baking has been completed, and the
separation of the product and pans has been accomplished, the pans are washed and
greased to be used over again. Pan wash-water has been found to be a very strong
and refractory waste in terms of its biochemical oxygen demand.
Fruit, nuts, and other nutritional materials are often added to baked products
in order to enhance the product's taste. These additives are usually transported in
containers which require regular cleaning for sanitation. This wash water waste
mixed with the floor washings comprises another type of waste which is much weaker
in strength than the pan wash water, but, is usually much larger in volume.
Selection of Treatment Process
Treatment processes for bakery wastes have received relatively little investigation in the past. The primary reason has probably been that bakeries are usually
located near high density population areas, wastes are mixed and treated in conjunction with domestic waste products in municipal treatment plants.
Table I gives an analysis of typical washing compounds as used by sweet-goods
bakeries. In order to meet existing ground-water injection standards, it appeared that
washing compounds as shown in the tabulated composition would need only minor
modification to eliminate use of chromates as corrosion inhibitors and to replace
these with nitrites. No standards in N. Y. State indicated any undesirability of
phosphates as constituents of cleansers or of baking mixes.
At the investigated bakery, six items were reported to be in general production: 1) sweet bread and roUs; 2) coffee cakes; 3) pies; 4) fruited cake; 5) fried
goods (doughnuts); and 6) cookies. There seemed to be no direct relationship between total production and total quantities of waste water.   However, there was an
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