Section Four
PULP AND PAPER MILL WASTES
50 TREATMENT OF PULP AND PAPER MILL WASTEWATERS
FOR POTENTIAL WATER REUSE
William R. Knocke, Associate Professor
Deepak Bhinge, Graduate Assistant
Elizabeth Sullivan, Graduate Assistant
Gregory D. Boardman, Associate Professor
Department of Civil Engineering
Virginia Tech University
Blacksburg, Virginia 24061
INTRODUCTION AND OBJECTIVES
The pulp and paper industry uses large volumes of water in the pulp and bleaching process, with
values ranging from 15,000 to 60,000 gallons per ton of bleached pulp [1]. Some of the wastewater
pollutants generated by this industry include color, dissolved inorganic solids and organic carbon.
Treatment of these wastewaters to reduce the quantity of each pollutant is necessary if the water is to
be recycled back to various stages of the process. Also, in certain instances, treatment for the removal
of these particular classes of pollutants may be required prior to release in public waterways.
Major sources of color from a pulp mill include the caustic extraction stage in bleaching, the
unbleached screenings, and the decker filtrates [2]. Significant amounts of the colored material were
felt to originate from lignin and its derivatives. Fuller et al. [3] reported that, in addition to lignin,
tannins reacting with iron as well as the natural color bodies of the wood also add to the effluent color
level. Schmidt and Joyce [4] showed that the functional groups which contribute the greatest amount
of color to pulping and bleaching effluents are aromatic and quinonoid nuclei which may be conjugated with carbonyl and ethylenic groups. Also, the authors indicated that the color bodies present in
these effluents vary in molecular weight from less than 400 up to 150,000 mass units.
A variety of wastewater treatment options are available for use in the treatment of pulp and paper
effluents. For the control of color and organic carbon concentrations, processes such as chemical
coagulation, chemical oxidation, ultrafiltration, biological treatment, and activated carbon addition
have been used with varying degrees of success. For the reduction of dissolved inorganic solids
concentrations, ion exchange and reverse osmosis have been effectively used in certain cases. Reduction of dissolved species concentrations such as chlorides is important related to corrosion concerns
Table I. Water Quality Requirements for Recycle |8|
Parameter TAPPI E603 Specifications (mg/L)
Turbidity 25
True Color (Pt-Co units) 5
TDS 250
Total Hardness 100
Free C02 10
Fe 0.1
Mn 0.05
CI 75
Alkalinity 75
Silica as SiO, 20
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