45    ANAEROBIC TREATMENT OF CANNERY INDUSTRY
WASTEWATERS
Eugenio Foresti, Associate Professor
University of Sao Paulo
Sao Carlos School of Engineering
Av. Dr. Carlos Botelho, 1465
13560-Sao Carlos-SP-Brazil
INTRODUCTION
The nature of the organic matter of cannery industry wastewater makes them suitable for biological
treatment, specially because they rarely present toxicant or inhibitory compounds in their composition. In fact, preparation and operations for processing animal and vegetable raw materials into
edible products scarcely make use of chemicals. Thus, wastewater characteristics are mainly related to
the nature of the organic matter processed. Normally, the only operations which necessarily use
chemicals are the cleaning and sterilization of equipment, floors, and walls. The use of disinfectants
and caustic soda at the end of each working cycle results in short-time concentrated discharges, and
may lead to operational problems for those wastewater treatment plants which are not protected
against shock-loads. However, flow equalization and influent pH control normally have enough
diluting and neutralizing effect to permit the use of biological processes for cannery wastewater
treatment.
Until recently, aerobic processes have been considered the most convenient method to remove the
organic matter from cannery wastewaters. This trend has gradually changed since Young and
McCarty1 successfully made use of anaerobic filters for the treatment of soluble wastes. Following
their work, studies concerning the feasibility of anaerobic processes have been initiated all over the
world. According to Speece,2 there are several different anaerobic reactor configurations employed to
treat a large variety of industrial wastewaters. Nevertheless, most of the available data refer to lab-
scale plants, and an evident lack of information about scale-up criteria, and full-scale reactor performance still persists. This is particularly true in Brazil, where climate conditions are largely favorable
to the use of anaerobic processes.
This paper presents some performance data of anaerobic reactors used in the study of cannery
wastewater treatment carried out at the Sao Carlos School of Engineering (Brazil) since 1977.
PREVIOUS STUDIES
The first pilot anaerobic filter for industrial wastewater treatment in Brazil was installed at a meatpacking industry —Frigorifico Bordon —Sao Paulo.3 After five months of continuous operation,
BOD5 removal efficiency higher than 70% was achieved for the hydraulic retention time (HRT) of 12
hours (HRT) is always referred to the void volume in this paper). Based on the performance of the
pilot filter, full-scale plants were constructed to treat low-strength wastewater from soft-drink and
meat-packing industries. Campos et al.4 reported on five years operation of two full-scale anaerobic
filters constructed at a meat-packing industry. COD removal efficiency has been higher than 75%
(unfiltered samples) for HRT of 13h. In spite of the fact that the filters are not covered, no aggressive
odors have been detected in the treatment area.
Pivelli5 operated two lab-scale filters used for the treatment of potato processing wastewaters. For
organic loading rate (OLR) of 1,75 kg COD m"3d"', and HRT of 24h, BOD, removal efficiency
higher than 80% was achieved.
In 1983, an intensive research program on wastewater treatment was proposed to a cannery
industry — Conservas Alimenticias Hero S.A., in Sao Carlos, which mainly processes vegetables. It
included the design, construction, and operation of three anaerobic reactors at that industry: an
anaerobic filter (AF), a fluidized bed reactor (FBAR), and an up-flow anaerobic sludge blanket
reactor associated to an anaerobic filter (UASB/AF). For the AF, COD removal efficiency higher
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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