Biological Treatment of Strong Industrial
Waste from a Fiberboard Factory
M. NEPPER, A.  C. Br.
Union Allumettire
Overboelare, Belgium
THE PROBLEM
The Stream
The river Dender, along which is located our factory, has an extremely
variable flow. Since the river's headwater springs are rather weak, it is principally
fed by runoff. During the summer, the flow may well go down to 0. 07 cu m/sec
but rises after a rain, to five to 10 cu m/sec. After a couple of days without rain,
the flow falls back to the former level.
About the flow, all that once can say is that it varies in the summer (approximately from the beginning of May to the end of October) between 0.05 cu
m/sec and two cu m/sec, and that during the winter period it is generally between
two and 20 cu m/sec.
The mean flows, according to the Belgian Ministry of Public Health are the
following:
from   4/1 to 11/31 : 0.47 cu m/sec
from 12/1 to   3/31 : 3. 00 cu m/sec
Upstream of factory, the BODg is generally about four, the temperature
seldom exceeds 22 C, and the per cent/oxygen saturation varies between 70 and
90. Until about five years ago, we had to reckon with the wastes of beet sugar
manufacturers located upstream, but they now are working in a closed cycle.
There only remains, from time to time, and unexpectly the waste of a little detergent factory, which gives rise to a huge amount of foam on the river and in
our aeration basins.
The Pollution
In the fabrication of our board, named "Unalit, " we use the "wet" process
Aspluend-Defibrator. The shredded wood is defibrated wet, between rotating
disks, at a temperature between 170 and 190 c The fibers are then diluted with
recirculating water, raffinated, added with alum and eventually with some glue,
and then poured on a continuous forming machine at the dry end of which the cake
is cut to the desired length. The cake is then pressed at temperatures neighboring
after the defibrators. This carries away the soluble or solubilized materials from
wood. The main part of that water is recycled but, on one hand, mere is a small
amount evacuated from the cake during tne pressing and not recycled and, on the
other hand, owing to the fact that there is a continuous addition of fresh water,
there is also a continuous overflow of waste water.   It may be of interest to note
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