The Treatment of
Citrus Processing Waste Water
ROBERT R. MCNARY, Consultant Chemist
Fiske-Gay Associates, Inc.,
Orlando, Florida
INTRODUCTION
There are many things to consider in selecting waste water treatment
facUities for a citrus processing plant. The local conditions in, and around,
a plant dictate what types of waste treatment procedures may be used. One
must determine whether there is a large enough body of water to receive the
waste and give it the dilution required to prevent nuisance formation. Lacking this, is there a suitable area for sand absorption or spray irrigation? If
not, then some form of more intense treatment like trickling filters or activated sludge is required. Space for lagoons or polishing ponds, either alone,
or as adjuncts to other treatment, may also be considered.
In the case of Kraft Foods, Citrus Division, located just west of Lakeland, Florida, the receiving stream is little more than an irrigation ditch,
indicating that the waste water treatment must be thorough. The land is low
and subject to flooding after heavy rains. Sand absorption and spray irrigation
are therefore ruled out. The Zimmermann process, a wet chemical oxidation, requires a larger volume of strong waste to make it economicaUy
practicable. Of the two remaining processes under consideration, activated
sludge was selected for this application because it needs less capital investment and can be installed on a smaller ground area and can be made more
flexible.
CHARACTERISTICS OF CITRUS PROCESSING WASTE WATER
The waste water from citrus processing, in general, may be considered
to be the equivalent of citrus juice (orange or grapefruit) with a certain
amount of water added to adjust the concentration. In addition, at times,
alkalis and detergents may be present. The strength of the waste water is influenced by the processing operation from which it originates (see Table I).
In terms of volume, the principle products of citrus processing are canned
single strength juice, "chilled" juice, frozen concentrated juice, canned
sections, "chilled" sections, and cattle feed from the dried peel.
About two-thirds of the total solids in citrus juices are sugars and the
same may be said of citrus waste water. Because of this, citrus wastes are
highly putrescible. Citrus waste water contains pectic substances which interfere with settling of the suspended sofids. Primary clarification of citrus
waste water is not as effective as with most other wastes. Citrus waste water
contains a small amount of the essential oil that occurs mostly in the fruit
peel. This oil is bacteriostatic but usually does not interfere with treatment
procedures unless it accumulates in an anaerobic digester. Citrus wastes are
deficient in nitrogen and phosphorus compounds. Treatment by biological
procedures may be accelerated by adding these nutrients. Citrus waste water
is usually somewhat acid because of the citric acid it contains. However,
alkaline materials used in cleaning the equipment and lye-bath water from
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