Refinement of Purified Sewage for Unrestricted Industrial Use
635
In the process of papermaking, alum is used in conjunction with rosins as sizing
material. This treatment imparts the desired writability characteristics to the finished
paper. Certain organic impurities, present in process water, are precipitated during this
sizing process by the addition of alum. The alum flocculation/flotation process removes
these objectionable organic constituents before the process water enters the mill.
Unwanted reduction in paper brightness is thereby eliminated.
Lime treatment, by and large, probably removes the same objectionable organic
impurities as the alum process. No investigations have yet been carried out into the nature
of these organics, which contribute only about 40 per cent of the COD originally present.
The alum-flotation process has on a large scale proved that it is possible to reclaim
from purified sewage a process water suitable for the unrestricted industrial use
throughout all sections of the pulp and paper mill. One benefit from this process is the
saving of nearly 2 c/m
3 on reclaimed process water as compared with RWB water;
another one is the conservation of the limited fresh water supply which is of great
importance in a semi-dry country like South Africa subject to recurrent long periods of
acute water shortage.
The success of the alum flocculation/flotation process to upgrade the quality of
conventionally treated sewage effluent makes it possible to exploit the full potential of
available sewage for industrial reuse in pulp and papermaking. To allow for future
expansion SAPPI has acquired the option on further quantities of sewage from the sewage
works of an adjacent town amounting to a further 10,000 m
3 /day.
CONCLUSIONS
(1) Alum treatment of purified sewage effluent makes it possible to use sewage for
industrial purposes at an economic price.
(2) Although alum treatment of purified sewage effluent does not remove heavy metals
as effectively as lime treatment, the reclaimed sewage water is of such a good quality that
it can be used without restrictions in all sections of the pulp and paper mill.
(3) Water quality criteria as reported in literature are often not correct and must be
revised according to specific circumstances.
ACKNOWLEDGEMENTS
The authors wish to thank Mr. L.A. Job, Technical Director of SAPPI, Mr. Chris J.
Myburgh and the other personnel of SAPPI who played an active role in the research and
implementation of the scheme, for their assistance and guidance in preparing this paper.
Thanks are also due to Dr. G.J. Stander, former Director of the National Institute for
Water Research, who encouraged the progress of industrial water reclamation.
REFERENCES
1 U.S. Bureau of the Budget. Office of Statistical Standards, Technical Committee on Industrial
Classification, Standard Industrial Classification Manual, amended to 1963.
2 EMERSON, R.E. and FREEDMAN, H., Production of bleached pulps using water with high color
content, TAPPI, vol. 54, No. 6 (June 1971).
635
In the process of papermaking, alum is used in conjunction with rosins as sizing
material. This treatment imparts the desired writability characteristics to the finished
paper. Certain organic impurities, present in process water, are precipitated during this
sizing process by the addition of alum. The alum flocculation/flotation process removes
these objectionable organic constituents before the process water enters the mill.
Unwanted reduction in paper brightness is thereby eliminated.
Lime treatment, by and large, probably removes the same objectionable organic
impurities as the alum process. No investigations have yet been carried out into the nature
of these organics, which contribute only about 40 per cent of the COD originally present.
The alum-flotation process has on a large scale proved that it is possible to reclaim
from purified sewage a process water suitable for the unrestricted industrial use
throughout all sections of the pulp and paper mill. One benefit from this process is the
saving of nearly 2 c/m
3 on reclaimed process water as compared with RWB water;
another one is the conservation of the limited fresh water supply which is of great
importance in a semi-dry country like South Africa subject to recurrent long periods of
acute water shortage.
The success of the alum flocculation/flotation process to upgrade the quality of
conventionally treated sewage effluent makes it possible to exploit the full potential of
available sewage for industrial reuse in pulp and papermaking. To allow for future
expansion SAPPI has acquired the option on further quantities of sewage from the sewage
works of an adjacent town amounting to a further 10,000 m
3 /day.
CONCLUSIONS
(1) Alum treatment of purified sewage effluent makes it possible to use sewage for
industrial purposes at an economic price.
(2) Although alum treatment of purified sewage effluent does not remove heavy metals
as effectively as lime treatment, the reclaimed sewage water is of such a good quality that
it can be used without restrictions in all sections of the pulp and paper mill.
(3) Water quality criteria as reported in literature are often not correct and must be
revised according to specific circumstances.
ACKNOWLEDGEMENTS
The authors wish to thank Mr. L.A. Job, Technical Director of SAPPI, Mr. Chris J.
Myburgh and the other personnel of SAPPI who played an active role in the research and
implementation of the scheme, for their assistance and guidance in preparing this paper.
Thanks are also due to Dr. G.J. Stander, former Director of the National Institute for
Water Research, who encouraged the progress of industrial water reclamation.
REFERENCES
1 U.S. Bureau of the Budget. Office of Statistical Standards, Technical Committee on Industrial
Classification, Standard Industrial Classification Manual, amended to 1963.
2 EMERSON, R.E. and FREEDMAN, H., Production of bleached pulps using water with high color
content, TAPPI, vol. 54, No. 6 (June 1971).