Section 12. PULP AND PAPER MILL WASTES
FULL SCALE ANAEROBIC-AEROBIC BIOLOGICAL TREATMENT OF A
SEMICHEMICAL PULPING WASTE WATER
Angel Alejandro Velasco, Technical Director
Sociedad Anonima Industrias Celulosa Aragonesa (SAICA)
San Juan de la Pena 140
Zaragoza-2
SPAIN
Bjorn Frostell, Biochemical Engineer
AC Biotechnics AB
S-232 00 Arlov
SWEDEN
Mark Greene, Marketing Manager
AC Biotechnics, Inc.
Woodbury, New York 11797
INTRODUCTION
Anaerobic treatment of pulp and paper industry wastewaters is showing an ever-increasing interest. This is reflected in the fact that a conference was held in Tampere, Finland in 1985 [1) focusing
solely on anaerobic treatment of pulp and paper industry effluents.
Besides creating great interest, anaerobic treatment is beginning to be used on a full scale basis
in a number of cases [2-4]. The results in the full scale plants showing anaerobic technology should
be definitely recognized as a viable alternative to aerobic treatment in a number of cases. Certain
problems have to be seriously considered such as toxicity, nutrient and/or trace element deficiency
and odor.
AC Biotechnics—formerly AB Sorigona—has been deeply involved in anaerobic treatment of pulp
and paper mill effluents since 1980. Six pilot plant studies have been carried out and three full scale
plants are presently in operation [3,5,6], One of these full scale plants is located at the SAICA semi-
chemical pulp and paper mill in Zaragoza, Spain. It was started up in late April, 1984 and has received
full flow from the mill since August, 1984. In this paper, the SAICA mill and the results achieved
in the SAICA ANAMET plant will be presented.
THE SAICA MILL
SAICA is an integrated pulp and paper mill located in Zaragoza, Spain. It has a capacity of
225,000 tpy of corrugated medium, most of it 130 and 135 g/m2, and employed 250 people.
As is common in the Mediterranean countries, wood is scarce in Spain. Many mills have resorted
to waste paper as an alternative raw material, but that has strained the waste paper market. Though
the recovery rate is high (over 41% in 1984), almost 400,000 tons had to be imported last year, and
the market remains highly speculative, with strong price fluctuations.
To face those problems, SAICA uses three different types of raw materials. First, it has a recycled
paper line with a capacity of 150,000 tpy. Second, there is a semi-chemical pulp line of 35,000 tpy,
where rejects from saw-mills are cooked in an Escher-Wyss digester with caustic soda. Finally, there is
a straw pulp line of 90,000 tpy, also using caustic soda as a cooking agent. The digesters, developed and
patented by SAICA, work at atmospheric pressure and are provided with a counter-current washing
system. Either wheat or barley straw is used; most of it is collected—within a distance of 100 km from
the mill. The proportion of the three raw materials varies according to their relative prices and to the
desired characteristics of the paper; an average figure is 60% of waste paper, 33% of straw and 7% of
wood.
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