58     EFFECT OF ACID/BASE TREATMENT ON THE
DEWATERABILITY AND NUTRITIONAL QUALITY OF
BIOSOLIDS AS ANIMAL FOOD
L.D. le Roux, Graduate Research Assistant
J.B. Litchfield, Associate Professor
Department of Agricultural Engineering
University of Illinois at Urbana-Champaign
Urbana, Illinois 61801
R.L. Belyea, Professor
Department of Animal Science
University of Missouri
Columbia, Missouri 65211
M.E. Tuiiihleson. Professor
Department of Veterinary Biosciences
University of Illinois at Urbana-Champaign
Urbana, Illinois 61801
INTRODUCTION
Food processing plants generate an estimated 18 million tons of organic wastes each year.1
These wastes consist mainly of unused raw agricultural materials, fermentation residues, wash-
water biosolids, and microbial residues.2 Disposal of these solids is a significant environmental
problem. Traditional disposal methods, such as land application, landfills, and incineration, are
increasing in cost and becoming more restricted in use. For example, landfilling of biosolids is
no longer allowed in North Carolina and New Jersey, and banning of residuals disposal in landfills is likely to occur in more states as the number of landfills and their effective capacities continue to decrease.4-5 As a result, many wastewater treatment agencies will be forced to modify
their residuals management practices to comply with new regulations and to mitigate public concerns.
Biosolids, commonly known as waste activated sludge, or simply sludge,6 constitute a significant portion of the total solid wastes generated by food plants. The biosolids portion most likely
will increase in the future since more stringent effluent quality standards will be imposed on
wastewater treatment plants, which will result in the production of more biosolids.'1-7-8 Milk processing plant biosolids are high in protein content (= 35 to 45%); therefore, they can be recycled
as animal feed.'-9-10
Considerable research has been done on the chemical characterization, safety, and efficacy of
food plant wash water solids (biosolids) as animal feed."12 Clevenger" conducted a long-term,
comprehensive study to determine the safety and efficacy of food processing biosolids when
used as an animal food supplement. The biosolids were high in protein content, low in priority
pollutant concentrations (as specified by the EPA), and seemed well suited for use as animal
food. Several animal feeding studies have been conducted using biosolids from a milk processing plant.'-12 Biosolids (at 90% total solids [TS]) can be fed to sheep and swine in diets containing up to 20% biosolids, on a dry mass basis. Similar results were found when biosolids were fed
to cattle and sheep.9-10 One of the greatest disadvantages of biosolids as a protein source in animal food is their low protein solubility (=40%) compared to conventional protein supplements
such as alfalfa (96%) and soy bean hulls (94%).13
5/5/ Purdue Industrial Waste Conference Proceedings, 1996. Ann Arbor Press, Inc.. Chelsea. Michigan 48118.
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