TREATMENT OF A WOOD PRESERVING EFFLUENT CONTAINING
PENTACHLOROPHENOL BY ACTIVATED SLUDGE AND CARBON
ADSORPTION
B.E. Jank, Head
Biological Processes Section
PJ.A. Fowlie, Chemist
Wastewater Technology Centre
Environmental Protection Service
Environment Canada
Burlington, Ontario
INTRODUCTION
Regulations and guidelines for controding the wastewater from the wood preservation
industry are currently being considered by Environment Canada. In the event that it is decided to proceed with the development of effluent regulations/guidelines, it is necessary to
establish a data base in order to define best practicable technology (BPT) for the treatment
of wood preserving wastes. To accomplish this, the Wastewater Technology Center, Burlington, Ontario, undertook a comprehensive sampling and monitoring program at the activated
sludge system at Abitibi-Northern Wood Preservers Limited, Thunder Bay, Ontario.
The program was carried out from November 1, 1977 to May 1, 1978, and was divided
into three phases. The first phase involved the monitoring and upgrading of the existing
full-scale activated sludge system. In the second phase, the activated sludge effluent was
treated by a granular activated carbon column system. During the last phase of the study,
the activated sludge system was bypassed, and the wastewater, after od separation and flow
equalization, was treated in the activated carbon system directly.
The specific objectives of the study were to collect information which could be used in
the identification of BPT for the treatment of wood preserving wastes and to provide a data
base to be used in the development of regulations limiting the discharge of deleterious substances to the environment by this industry.
SOURCE OF WASTEWATER
The Abitibi-Northern Wood Preservers Limited, Thunder Bay, Ontario, preserves various
wood products such as telephone poles, radway ties and lumber for decks and wharfs. Three
different preservatives, pentachlorophenol (PCP), creosote and chromated copper arsenate
(CCA), are used in the wood preserving operation. Hydro poles are treated with PCP, radway
ties with creosote and lumber for decks and wharfs with CCA. Wood conditioning and treatment are carried out in three retorts. Creosote is used in two of the retorts, with the third
used for either PCP or CCA preservative. At the time of the study, the plant is processing
approximately 196,000 m3 of wood annually.
The wastewater discharged to the treatment plant is the condensate generated during
open steam conditioning The condensate is contaminated with water-soluble wood extractives, primardy carbohydrates. Because wood conditioning and treatment are carried out in
the same retort, the condensate generated fodowing treatment with the od-borne preservatives, creosote and PCP is highly contaminated. This problem does not exist fodowing treatment with CCA as the water4>orne preservative drains from the retort and is completely
recovered. The condensates produced during conditioning fodowing CCA treatment may
contain traces of chromium, copper and arsenic; however, they are generady considered to
be uncontaminated by the preservative.
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