A D V A N C E D T R E A T M E N T PROCESSES
AND W A S T E W A T E R RE-USE
THE FULL-SCALE REFINEMENT OF PURIFIED SEWAGE
FOR UNRESTRICTED INDUSTRIAL USE IN THE MANUFACTURE
OF FULLY BLEACHED KRAFT-PULP AND FINE PAPER
L.R.J. VAN VUUREN, J.W. FUNKE and L. SMITH
National Institute for Water Research of the South African Council
for Scientific and Industrial Research, PO Box 39S, Pretoria,
Republic of South Africa
INTRODUCTION
The ENSTRA Mill of South African Pulp and Paper Industries Ltd. (SAPPI), near the
city of Springs in Transvaal, South Africa is the only large manufacturing industry in this
country which, apart from several power stations, utilizes purified sewage as the major
part of its water supply. This reliance on purified sewage became a necessity since this
mill, on account of the favourable market situation, was established in the Witwatersrand
area with no river at the site for its water supply. Water of good quality, Rand Water
Board water, has to be obtained from pumping stations at the Vaal River, about 95 km
away. The only natural water available locally is of dolomitic origin and, therefore, too
hard for papermaking. Present daily production of ENSTRA is about 175 tons of
bleached Kraft pulp, 100 tons of semi-bleached Kraft pulp, 140 tons of fine paper and
200 tons of Newsprint. The mill receives certain supplies of unbleached pulp from another
SAPPI mill and services certain other Group paper mills by supplying their partial
requirements of bleached and semi-bleached pulp grades. The present rate of water usage
is made up of 16,000 m
3 /d (3.5 mil. g/d) Rand Water Board water and of 25,000 m
3 /d
(5.5 mil. g/d) purified sewage effluent from Springs.
During the earlier years when the brightness demands for fine bleached paper were not
as rigorous as today, the quality of the purified sewage water was satisfactory. With the
present demand for higher brightness paper it was, however, not uncommon to sacrifice 5
Elrepho units in brightness when purified sewage was used in bleaching. A quality survey
of Springs purified sewage over a number of years showed that, from the standpoint of
pulp and papermaking, the content of residual organic matter and of heavy metals was
objectionable. It was evident that the municipal sewage effluent which included industrial
waste water" from engineering and metal finishing operations and from a meat-packing
factory required further treatment to make it suitable for the unrestricted industrial use
within the pulp and paper mill. The Company, therefore, entered into a contract with the
National Institute for Water Research in order to try and solve its water quality problems.
At the same time, SAPPI intensified its own research into further treatment of sewage
effluent.
Based on these investigations, a full-scale treatment plant for the upgrading of the
purified sewage was put into operation in July 1970.
This paper deals with the pilot plant investigations which influenced the choice of the
full-scale treatment finally adopted, and with the operational results of the large-scale
(32,000 m
3 /d or 7 mgd) plant over the past year.
WATER QUALITY REQUIREMENTS
According to literature and to practical experience, important requirements for water
627
AND W A S T E W A T E R RE-USE
THE FULL-SCALE REFINEMENT OF PURIFIED SEWAGE
FOR UNRESTRICTED INDUSTRIAL USE IN THE MANUFACTURE
OF FULLY BLEACHED KRAFT-PULP AND FINE PAPER
L.R.J. VAN VUUREN, J.W. FUNKE and L. SMITH
National Institute for Water Research of the South African Council
for Scientific and Industrial Research, PO Box 39S, Pretoria,
Republic of South Africa
INTRODUCTION
The ENSTRA Mill of South African Pulp and Paper Industries Ltd. (SAPPI), near the
city of Springs in Transvaal, South Africa is the only large manufacturing industry in this
country which, apart from several power stations, utilizes purified sewage as the major
part of its water supply. This reliance on purified sewage became a necessity since this
mill, on account of the favourable market situation, was established in the Witwatersrand
area with no river at the site for its water supply. Water of good quality, Rand Water
Board water, has to be obtained from pumping stations at the Vaal River, about 95 km
away. The only natural water available locally is of dolomitic origin and, therefore, too
hard for papermaking. Present daily production of ENSTRA is about 175 tons of
bleached Kraft pulp, 100 tons of semi-bleached Kraft pulp, 140 tons of fine paper and
200 tons of Newsprint. The mill receives certain supplies of unbleached pulp from another
SAPPI mill and services certain other Group paper mills by supplying their partial
requirements of bleached and semi-bleached pulp grades. The present rate of water usage
is made up of 16,000 m
3 /d (3.5 mil. g/d) Rand Water Board water and of 25,000 m
3 /d
(5.5 mil. g/d) purified sewage effluent from Springs.
During the earlier years when the brightness demands for fine bleached paper were not
as rigorous as today, the quality of the purified sewage water was satisfactory. With the
present demand for higher brightness paper it was, however, not uncommon to sacrifice 5
Elrepho units in brightness when purified sewage was used in bleaching. A quality survey
of Springs purified sewage over a number of years showed that, from the standpoint of
pulp and papermaking, the content of residual organic matter and of heavy metals was
objectionable. It was evident that the municipal sewage effluent which included industrial
waste water" from engineering and metal finishing operations and from a meat-packing
factory required further treatment to make it suitable for the unrestricted industrial use
within the pulp and paper mill. The Company, therefore, entered into a contract with the
National Institute for Water Research in order to try and solve its water quality problems.
At the same time, SAPPI intensified its own research into further treatment of sewage
effluent.
Based on these investigations, a full-scale treatment plant for the upgrading of the
purified sewage was put into operation in July 1970.
This paper deals with the pilot plant investigations which influenced the choice of the
full-scale treatment finally adopted, and with the operational results of the large-scale
(32,000 m
3 /d or 7 mgd) plant over the past year.
WATER QUALITY REQUIREMENTS
According to literature and to practical experience, important requirements for water
627