THERMAL DESTRUCTION OF CHLOROPHENOL RESIDUES
Trevor R. Bridle, Head
Herbert W. Campbell, Engineer
Residue Management Section
Wastewater Technology Centre
Environment Canada
Burlington, Ontario L7R 4A6
Ashok K. Sachdev, Research Scientist
Dearborn Environmental Consulting Services
Mississauga, Ontario L5A 3T5
INTRODUCTION
Approximately 3,300 tonnes of chlorophenols are used annually in Canada, with greater than 90%
used for wood protection and preservation. Residues from the wood protection and preservation
industries are contaminated with chlorophenols and pose a serious disposal problem. The residues of
major concern are dip tank sludges and wood shavings which can contain total chlorophenol concentrations of up to 35,000 mg/kg. In eastern Canada most of the residues are land disposed, whereas in
western Canada the most widely used disposal option is burning in open tee-pee burners or as supplementary fuel in hog-fuel or other industrial boilers. These burning practices have been questioned
both from the viewpoint of destruction of parent chlorophenols and also because of concern that
more hazardous products of incomplete combustion, such as dioxins may be formed. The limited data
base suggests that concern may be warranted on both accounts.
Ahling and Johansson [1] studied the destruction of chlorophenols at both pilot and full scale.
Their results, although somewhat conflicting, suggested that both tetra (T4CP) and pentachloro-
phenol (PCP) could be destroyed (>99.9%) provided suffient contact time (*3 seconds) could be
maintained at temperatures between 600 C and 800 C. Controlled air incineration of pentachloro-
phenol treated wood wastes has also recently been conducted [2]. This study indicated no residual
pentachlorophenol in the effluent after exposure to 980 C for a retention time of 2.5 seconds. Of more
concern is the documented evidence of dioxin formation during the burning of chlorophenols. Rappe
et al [3] have demonstrated that burning of trichlorophenol produces significant quantities of tetra-
chlorodibenzo-p-dioxins (TCDDs) and burning PCP produces significant quantities of octachlorodi-
benzo-p-dioxin (OCDD).
The data base generated to date has been developed under nonideal conditions, especially those
data collected from full scale facilities. In general, full scale industrial boilers currently burning
chlorophenol wastes are not operated under controlled conditions; therefore, the data generated is of
limited value. However, based on this limited data, it appears that burning can be an acceptable
method of disposing of chlorophenols, provided conditions that ensure destruction of both
chlorophenols and products of incomplete combustion can be maintained. For incineration to be
environmentally acceptable, a sound data base, with respect to the thermal decomposition of
chlorophenols, is required. This data base can best be developed at laboratory scale and is the basis of
this investigation.
PROJECT RATIONALE AND OBJECTIVES
As discussed above, there is at present no precise data in the literature defining the thermal
destruction behavior of pure chlorophenols. Extensive laboratory research to develop gas phase
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