26    ALTERING TEXTILE MANUFACTURE TO MINIMIZE
TREATMENT NEEDED FOR WASTEWATER
RECLAMATION
Maria Eduarda de C. Beja Neves, Assistant Professor
Technical University of Lisbon
Lisbon, Portugal
James E. Etzel, Professor
School of Civil Engineering
Purdue University
West Lafayette, Indiana 47907
INTRODUCTION
Purpose
The research involved two major areas of water management in the textile industry: wastewater
reclamation and chemical substitutions.
The approach used relates to important management decisions faced by the industry today: minimization of the use of external sources of water, and substitution of process chemicals in order to make
their removal from wastewaters easier and, ultimately, to protect the environment.
A linear programming model was developed, capable of minimizing the cost of treatment needed
for wastewater reclamation. This was accomplished through the selection of the optimum set of
chemicals in respect to their removal from a wastewater by biodegradation, and by so doing, preventing the accumulation of inorganic dissolved solids in the reused wastewater, even with prolonged
reuse.
The need for minimizing the accumulation of inorganic dissolved solids is that they cause excessive
wear and corrosion on machinery. In addition, the cost of removing dissolved solids, and the problems associated with their final disposal, are difficult and costly, especially if the solids are inorganic
in nature. Hence, the general basic approach was to establish the interrelationship between the
characteristics of the chemicals used in the production processes with their removal from the plant's
wastewaters, along with the suitability of the treated wastewaters for reuse within production
processes.
The in-plant approach was the selection of the chemicals used in the various industrial processes
based on consumption and their organic and inorganic composition. In this approach, which has been
used full scale in other industries, the means of controlling dissolved solids was through the use of
biological wastewater treatment.
Biological wastewater treatment not only removes the organic dissolved solids, but converts them
into a biological sludge which is disposable in the environment much more readily than would be a
concentrated brine coming from processes such as deionization or reverse osmosis. The cost of
biological treatment is also lower than the cost of other dissolved solids removal processes and much
less complicated to operate.
In other full scale uses of this approach to water reuse, reuse rates as high as 96 to 98% have been
achieved on a sustained basis.
Different values were tested for the wastewater reclamation rate, and for the percentage of biodegradable materials in the chemicals used by the industry.
The industrial processes themselves were considered as blocks, with different manufacturing objectives and using different kinds and quantities of chemicals.
The cost of wastewater treatment was influenced by the organic content of the chemicals and by the
wastewater reclamation rate.
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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