55    TREATMENT OF FOREST INDUSTRY WASTEWATERS IN
MOVING BED BIOFILM REACTORS
Lars J. Hem, Senior Scientist
Bjrfrn Rusten, Professor
Aquateam-Norwegian Water Technology Centre A/S
0604 Oslo, Norway
Astrid Broch-Due, Senior Development Engineer
Norske Skogindustrier AS Norske Skog Teknikk
1324 Lysaker, Norway
Erik Mattsson, Project Manager
Research and Development, Environmental Engineering
Stora Technology
791 80 Falun, Sweden
Thorbjrirn Westrum, Managing Director
Kaldnes Miljekeknologi
3103 Tdnsberg, Norway
INTRODUCTION
Due to limits for maximum allowable wastewater discharges from the forest industry, several mills
have invested in biological wastewater treatment. Suspended growth systems, such as aerated lagoons
and conventional activated sludge plants, are used in the majority of these treatment plants. The
suspended growth systems require large volumes and they are hampered by sludge bulking which
causes sludge loss to the effluent. The sludge bulking and sludge loss to the effluent seem to be a
major problem with respect to treating pulp and paper mill wastewater.1
Biological fixed film processes have the advantage that they can be volume efficient and that
washout of the biomass will not occur. In conventional biofilm processes, such as trickling filters and
submerged aerated biofilters, channeling or clogging of the media may occur. To avoid these problems, a more volume efficient moving bed biofilm process was developed.
THE MOVING BED BIOFILM REACTOR
In the moving bed biofilm reactor (MBBR), the biomass is attached to small plastic elements which
move freely along with the water in the reactor. The displaced water volume due to the carriers is
11-13%, giving a biofilm surface of about 350 m2/m3. Being a biofilm reactor, there is no sludge
recycling. The carrier and the principle for the movement of the carriers in the reactors are shown in
Figure 1.
The MBBR may be used for several purposes, including nitrification in domestic wastewater,2,3
nitrogen removal from domestic wastewater,4 treatment of dairy and potato processing wastewater,5,6
or treatment of forest industry wastewater.7,8 Ten full scale plants have been built; five plants for
treatment of domestic wastewater, two plants for treatment of forest industry wastewater, and three
plants for treatment of dairy and potato processing wastewater. In addition, several plants are
presently under construction.
Data from pilot tests and preliminary full scale operation of the two full scale plants treating forest
industry wastewater will be presented here. Flow sheets of the full scale plants are shown in Figure 2.
49th Purdue Industrial Waste Conference Proceedings, 1994 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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