604
Discussion
REFERENCES
1 National Council for Air and Stream Improvement, Technical Bulletin No. 157 (1962).
2 U.S. Patent No. 31120,464(1964).
3 National Council for Air and Stream Improvement, Technical Bulletin No. 157 (1962) Ref: 11, 21,
3 4 , 3 5 , 3 6 , 3 7 , 3 8 , 4 3 , 4 6 .
4 TYLER, M.A. & FITZGERALD, A.D. Review of color reduction technology in pulp and paper
effluents, 58th Annual general meeting, Technical Section (1971) Canadian Pulp & Paper
Association.
5 U.S. Patent No. 2,846,811(1958).
6 FULLER, R.R. Color removal from kraft effluents, Southern Pulp & Paper Manufacturer,
September 10, 1971.
7 U.S. Patent No. 3,627,679(1971).
8 National Council for Air and Stream Improvement, Technical Bulletin No. 253 (1971) Instigation
into improved procedures for measurement of mill effluent and receiving water color.
9 National Council for Air and Stream Improvement, Technical Bulletin No. 239 (1970) Mechanisms
of color removal in the treatment of pulping and bleaching effluents with lime.
10 DAVIS Jr., C.L. TAPPI, Vol. 2, Page 1923 (October 1969) Tertiary treatment of kraft mill effluent
including chemical coagulation for color removal.
11 GOULD, M. Physio-chemical treatment of kraft mill effluent, 25th Industrial Waste Conference,
Purdue University, 1970.
12 U.S. Patent No. 3, 531, 370 (1970).
13 U.S. Patent No. 3,639,206.
14 GOULD, M. New lime process for removal of color from kraft mill effluent 8th Annual TAPPI
Environmental Conference (1972).
Discussion by R. L. Sanks*
At the present time the most promising processes for the removal of color from kraft bleach wastes
are: massive lime precipitation, carbon sorption, oxygen bleaching (which produces no color), ion
exchange, and reverse osmosis. In the massive lime process patented by Berger, Gehm, and Herbet ,
the color is removed.by precipitation using the entire lime budget of the plant. The precipitated lime is
then dewatered and used to recausticise the green liquor. The color bodies dissolve in the white liquor
and are burned with the black liquor in the recovery furnace. The lime mud is recalcined in the kiln as
usual. The advantages of the process are: little extra energy is needed, there is no interference from the
color bodies, the loss of chemicals is small, and the process integrates easily into the existing pulp
process so the only additional equipment is an extra sedimentation basin and, usually, a vacuum filter.
The process is flexible. For example, a recarbonation step and a second sedimentation basin can be
added to improve lime recovery.
There are several difficulties in the reuse of bleach plant waste water including (in order of
importance) slime, suspended solids, color, total dissolved solids, foaming, corrosion (due mostly to
chlorides) and scale. Therefore, greater refinement such as, for example, sorption, ion exchange, or
reverse osmosis is needed. Either granular or powdered carbon can be used for polishing the liquor
after massive lime precipitation. A promising new development for treating either raw or pretreated
liquor is the manufacture of carbon by "scorching** (partially burning) the black liquor to produce
carbon, utilizing the carbon for the sorption of color, and then completely burning the carbon and
sorbed organics for heat recovery. Ion exchange can also be used to polish the pretreated liquor, and
the Rohm and Haas Company
2 has developed a resin to decolor raw wastes. Demineralization can be
accomplished by ion exchange or reverse osmosis. Pretreatment to protect membranes in the reverse
osmosis process may not be necessary
3 .
Color Removal with Lime
At Montana State University, recycling and reuse of wastes is under study using bleach waste
waters obtained from the Hoerner-Waldorf Corporation Pulp Plant in Missoula, Montana. Good
housekeeping and extensive counter-current flow results in effluent volumes only one-third of those
the authors report, and the color is approximately five times as great. Contrary to the authors'
experience with poor settling of lime precipitates, the writer's experience (substantiated by many
others) shows good settlement and color removals up to 95 percent or more.
* Professor of Civil Engineering and Engineering Mechanics, Montana State University, Bozeman,
Montana.
Discussion
REFERENCES
1 National Council for Air and Stream Improvement, Technical Bulletin No. 157 (1962).
2 U.S. Patent No. 31120,464(1964).
3 National Council for Air and Stream Improvement, Technical Bulletin No. 157 (1962) Ref: 11, 21,
3 4 , 3 5 , 3 6 , 3 7 , 3 8 , 4 3 , 4 6 .
4 TYLER, M.A. & FITZGERALD, A.D. Review of color reduction technology in pulp and paper
effluents, 58th Annual general meeting, Technical Section (1971) Canadian Pulp & Paper
Association.
5 U.S. Patent No. 2,846,811(1958).
6 FULLER, R.R. Color removal from kraft effluents, Southern Pulp & Paper Manufacturer,
September 10, 1971.
7 U.S. Patent No. 3,627,679(1971).
8 National Council for Air and Stream Improvement, Technical Bulletin No. 253 (1971) Instigation
into improved procedures for measurement of mill effluent and receiving water color.
9 National Council for Air and Stream Improvement, Technical Bulletin No. 239 (1970) Mechanisms
of color removal in the treatment of pulping and bleaching effluents with lime.
10 DAVIS Jr., C.L. TAPPI, Vol. 2, Page 1923 (October 1969) Tertiary treatment of kraft mill effluent
including chemical coagulation for color removal.
11 GOULD, M. Physio-chemical treatment of kraft mill effluent, 25th Industrial Waste Conference,
Purdue University, 1970.
12 U.S. Patent No. 3, 531, 370 (1970).
13 U.S. Patent No. 3,639,206.
14 GOULD, M. New lime process for removal of color from kraft mill effluent 8th Annual TAPPI
Environmental Conference (1972).
Discussion by R. L. Sanks*
At the present time the most promising processes for the removal of color from kraft bleach wastes
are: massive lime precipitation, carbon sorption, oxygen bleaching (which produces no color), ion
exchange, and reverse osmosis. In the massive lime process patented by Berger, Gehm, and Herbet ,
the color is removed.by precipitation using the entire lime budget of the plant. The precipitated lime is
then dewatered and used to recausticise the green liquor. The color bodies dissolve in the white liquor
and are burned with the black liquor in the recovery furnace. The lime mud is recalcined in the kiln as
usual. The advantages of the process are: little extra energy is needed, there is no interference from the
color bodies, the loss of chemicals is small, and the process integrates easily into the existing pulp
process so the only additional equipment is an extra sedimentation basin and, usually, a vacuum filter.
The process is flexible. For example, a recarbonation step and a second sedimentation basin can be
added to improve lime recovery.
There are several difficulties in the reuse of bleach plant waste water including (in order of
importance) slime, suspended solids, color, total dissolved solids, foaming, corrosion (due mostly to
chlorides) and scale. Therefore, greater refinement such as, for example, sorption, ion exchange, or
reverse osmosis is needed. Either granular or powdered carbon can be used for polishing the liquor
after massive lime precipitation. A promising new development for treating either raw or pretreated
liquor is the manufacture of carbon by "scorching** (partially burning) the black liquor to produce
carbon, utilizing the carbon for the sorption of color, and then completely burning the carbon and
sorbed organics for heat recovery. Ion exchange can also be used to polish the pretreated liquor, and
the Rohm and Haas Company
2 has developed a resin to decolor raw wastes. Demineralization can be
accomplished by ion exchange or reverse osmosis. Pretreatment to protect membranes in the reverse
osmosis process may not be necessary
3 .
Color Removal with Lime
At Montana State University, recycling and reuse of wastes is under study using bleach waste
waters obtained from the Hoerner-Waldorf Corporation Pulp Plant in Missoula, Montana. Good
housekeeping and extensive counter-current flow results in effluent volumes only one-third of those
the authors report, and the color is approximately five times as great. Contrary to the authors'
experience with poor settling of lime precipitates, the writer's experience (substantiated by many
others) shows good settlement and color removals up to 95 percent or more.
* Professor of Civil Engineering and Engineering Mechanics, Montana State University, Bozeman,
Montana.