Section Six
INDUSTRIAL WASTES
B. PULP AND PAPER
61    COLOR TREATMENT OF A DYE-BEARING PAPER MILL
WASTEWATER: A CASE STUDY
Hugh G. Tozer, Project Engineer
Woodard & Curran Inc.
Portland, Maine 04102
INTRODUCTION
A New England paper mill manufactures colored paper from pulp produced at another mill. The
operation generates wastewater of various colors due to residual dyes. The mill screens and clarifies its
wastewater, but the treatment system currently lacks an effective color removal process. The effluent
discharges to a local river which naturally has a muddy brown-green color. Although the turbid river
water typically obscures the colored effluents, some colors are visible. These discharges are infrequent
and not toxic, but they have raised aesthetic environmental concerns.
The mill addressed these concerns by initiating a two-phase benchscale investigation of various
color removal processes. In Phase 1, three general processes were screened to identify possible -
treatment units that could be added to the existing plant system. These processes included:
• Coagulation using alum with and without an anionic flocculant;
• Adsorption using powdered activated carbon and activated alumina; and
• Oxidation using sodium hypochlorite and ozone.
Each process was evaluated in terms of its ability to remove color, by-products (e.g., sludge),
relative costs and operational ease. The results of Phase 1, presented herein, determined that oxidation processes had several advantages over coagulation and adsorption. Neither chlorine bleaching
nor ozonation generated sludge and both were relatively simple to control.
Chlorine bleaching and ozonation were further examined in Phase 2. Additional benchscale tests
were performed and the effluents were tested for aquatic toxicity. The results of Phase 2, also
discussed herein, demonstrated that both processes could safely remove color. The costs of chlorine
bleaching were estimated to be significantly lower than ozone treatment. However, due to industry
and public concerns about chlorine, ozone may prove a more suitable long term treatment process for
color removal.
METHODS AND MATERIALS
The bench-scale investigation of different color removal processes involved many distinct methods
and materials. Table I lists each experiment by the chemicals used, the treatment process, the range of
doses and the study phase(s) in which the tests were performed. The approaches used in these
experiments and their results are reported under the RESULTS section. Topics common to all of the
tests, such as the color measurement techniques, are described below.
Wastewater Samples
Wastewater samples for both study phases were collected from the existing treatment system after
screening and before clarification. They were stored at ambient temperatures in sealed plastic drums
until tested.
t8th Purdue Industrial Waste Conference Proceedings, 1993 Lewis Publishers, Chelsea, Michigan 48118. Printed in
J.S.A.
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