TREATMENT OF CORK-STOPPER
MANUFACTURING WASTES
George K. Anderson, Senior Lecturer
Division of Public Health Engineering
University of Newcastle-upon-Tyne
Newcastle-upon-Tyne, United Kingdom
Chia-Yau Cheng, Engineer
Antonio Costa Pinto, Chief Engineer
HIDURBE, Hydraulic Consultants
Porto, Portugal
Cork processing and cork stopper manufacture has been an important industry in Portugal since the fourteenth century. The current annual production of Portuguese cork is about
170,000 metric tons, accounting for about half of the world's total output [ 1 ]. One of the
m^jor areas of the cork processing industry in Portugal is in the region between S. Joao da
Madeira and Vila da Feira, where approximately 200 processing plants of various capacities
are in operation.
In the same region are a number of other industries, including paper mills and tanneries,
the majority of which are small- to medium-scale operations. The population is widely
dispersed in relatively small communities with a large proportion being without either a
satisfactory wastewater collection system or treatment plant. As a result of these discharges
of untreated domestic and industrial wastewaters, water pollution has reached an intolerable
level. As a result of this, a preliminary investigation was made by a Portuguese consulting
engineering organization, HIDURBE, in collaboration with the University of Newcastle-
upon-Tyne, into ways in which the problem could be alleviated. It soon became very apparent that the cork industry was a major problem, not only due to the number of factories
but also to the nature of the wastewater and the lack of any previous studies or information. A proposal was consequently made to Junta Nacional de Investigacao Cientifica Tecno-
logica (JNICT) to provide financial assistance for carrying out an investigation into the
various possibilities for the treatment and disposal of these wastewaters.
This chapter presents the results and conclusions of the study so far and indicates the
philosophy of the approach to this type of industry together with suggested solutions to
the overall problem.
CORK STOPPER MANUFACTURE AND WASTEWATERS
The Process
Cork is produced from the bark of cork-oak trees and is an industry confined largely
to southern Europe and North Africa. Figure 1 represents a schematic diagram of the major
stages in cork-stopper production and finishing. The bark is stripped from the tree and cut
into slabs for transport to the processing plant. The selected slabs are boiled in large tanks
to allow the cork to expand and, after grading, the slabs are piled in storage for about three
weeks to dry. Stoppers are punched from the slabs, after which they are immersed in
chlorination tanks containing a mixture of lime and chlorine. The low-grade cork slabs and
residual cork chips from the punching operation may also be treated in this way before
being processed as a by-product into materials such as cork tiles or insulation.
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