water have both economic and environmen-
tal consequences concerning treatability and
disposal. Economics of treatment are
affected by the amount of product loss from
the processing operations and by the treat-
ment costs of this waste material. Significant
characteristics that determine the cost for
wastewater treatment are, the relative
strength of the wastewater and the daily vol-
ume of discharge.
These residues are normally destined to
the biological system after screening and
decantation for the removal of solids.
According to Veras (2003), many food
processors do not use decantation before
sending these wastes to municipal sewer
treatment resulting in an increase of dis-
solved solids, hindering purification, and
increasing equipment maintenance and
energy consumption for treatment because
of larger density residues.
The largest volume of solid residues in
wastewater is composed of residues from
sieves, flotation sludge, and waste from the
biological processes involved. Sieve residues
and flotation sledge have value as a by-prod-
uct because they can be converted to animal
foods and fertilizer. However, sludge through
the use of chemical flotation that incorpo-
rates metallic coagulants should not be used
for animal food.
Wastewater can be salvaged through recy-
cling, reuse, and the recovery of solids. The
degree of conservation and salvage value of
wastewater is based on factors such as waste-
water treatment facilities for recoverable
materials, operating costs of independent
treatment, market value of the recoverable
materials, local regulations regarding efflu-
ent quality, surcharge cost for plants dis-
charging into public sewers, and anticipated
discharge volume in the future. The econom-
ics of disposal of solids, concentrates, blood,
and concentrated stick (in wet rendering)
determine how much of these polluting
solids are kept out of the sewer. A waste-
water control plan must be able to remove
and convey organic solids using “dry” meth-
ods, without discharging those solids to the
sewer and by using a minimal amount of
water in the cleaning operation.
Spent cleaning compounds and sanitizers
are discharged into waste treatment facilities.
The toxicity of these materials causes con-
cern because sanitizers, which destroy
microorganisms, are toxic by definition.
However, they meet requirements of the
Food and Drug Administration (FDA) as an
indirect food additive because these organic
compounds are diluted in water and their
toxic properties become reduced to a safe
level. Many of the ingredients used in clean-
ing compounds and lubricants are generally
recognized as safe as food additives (Bakka,
1992). It appears that the major concerns for
wastewater treatment of this effluent are pH
fluctuation and possible long-term exposure
to trace heavy metals. However, these effects
can be controlled and waste minimized
through appropriate plant design and opti-
mal concentration use of cleaning com-
pounds and sanitizers.
Cleaning compounds and sanitizers
increase BOD/COD because they utilize sur-
factants, chelators, and polymers in addition
to organic acids and alkalis. Conveyor lubri-
cants utilize similar materials that increase
the BOD/COD of the effluent. However,
these compounds account for less than 10%
of the BOD/COD contributions from a food
processing plant. Water volumes associated
with sanitation from a food processing plant
can account for up to 30% of the total water
discharge. Because of the low BOD/COD
contributions, pH of wastewater is a major
concern.
A eutrophic condition can develop from
the discharge of biodegradable, oxygen-con-
suming compounds if inadequately treated
wastewater is discharged to a stream or otherWaste Product Handling 219