Wood preservation facilities, pentachlorophenol thermal: chapter F-9

9. Waste, Process Emissions and Disposal

For general information on process emissions and disposal, consult Section 9 of Part I, Chapter A - General Recommendations for All Wood Preservatives.

9.1 Control, Treatment and Disposal

The PCP oil-borne thermal treatment process generates solid wastes and emissions to air. Little liquid process wastewater may be generated from incidental infiltration. Numerous approaches are used or can be used by the industry to control, treat and/or dispose of the process wastes and emissions. Potential sources of chemical releases from PCP thermal treatment facilities are described in Section 5.2 and in Figure 1. Table 23 identifies the main categories of process wastes or emissions that can be generated at PCPT facilities, and summarizes recommended control, treatment and/or disposal methods.

The processes used for waste disposal fall under provincial jurisdiction and may vary from province to province.

Federal and provincial regimes address hazardous waste and hazardous recyclable material in different manners. Provincial requirements may also differ from province to province. Consult your provincial authority for more information.

Control Requirements

Control specifications will depend on factors such as the volume and frequency of the discharge and the sensitivity of the receiving environment. The discharge of chlorophenol-contaminated effluent into waters inhabited by fish is subject to the federal Fisheries Act. Refer to Table 3 for CCME water quality guidelines.

9.2 Waste Liquids Containing PCP

Liquid Process Wastes

Leaks and drips of oil solutions generally do not occur during the thermal treatment of wood. Frothing and/or overflow from the treatment tank can occur, however. The thermal tank should be designed to accommodate containment of such overflow. Structural defects in the treatment tank can also result in releases of oil solutions to groundwater. Containment shells are required in order to prevent groundwater contamination. Contaminated water solutions may be generated; these include washwaters and waters that infiltrate subgrade containment shells. Oil and PCP must be removed from these wastewaters prior to discharge (19, 28, 29). The techniques may include one or a combination of the following:

• gravity separation
• oil/water API separation, plate separation
• activated sludge treatment
• activated carbon treatment
• physical-chemical treatment (i.e. flocculation)
• evaporation/condensation

A regulatory discharge permit must be obtained for disposal of the treated aqueous wastes.

Contaminated Storm Runoff

Because thermal treatment facility sites are generally large, considerable volumes of storm runoff waters occur from these sites. Every precaution should be taken to avoid contamination of storm runoff water, particularly in the vicinity of PCP storage sites and treatment areas. Facility operators must acknowledge that there is a possibility of PCP-contaminated runoff from treated wood storage areas; surface runoff from the storage areas should therefore be monitored for chlorophenols and oil. See Section 7 for more details on design and equipment recommendations.

If contamination occurs, refer to Section 12 - Environmental Emergency Notification and Contingency Planning for more direction.

9.3 Solids with Potentially High PCP Concentrations

For the purposes of this document, solids with potentially high levels of PCP are defined as:

• sludges from work solution tanks and treatment tanks
• sludges from wastewater treatment processes (e.g. flocculated materials)
• unwashed containers or wrappings for PCP
• filters from cleaning vacuum

Sludges from thermal tanks constitute most of the solid wastes at thermal facilities. Operating and design modifications can be used to significantly reduce the volume of sludge. For example, open exposure of the tanks to precipitation leads to the generation of higher volumes of sludge. Roofing could eliminate this source of contamination.

Guidelines for the Disposal of Solid Wastes

While awaiting disposal, the contaminated solids should be in leakproof containers in a specially designed area that is curbed with a paved or concrete sealed surface. The area should be roofed to protect the wastes from precipitation. Any seepage or leachate generated at the site should be contained. Refer to Chapter A, Section 9, Table 23 - Recommended Practices for Handling Liquid & Solid Wastes and Sludge for complete details.

The most feasible disposal option for chlorophenol wastes appears to be high-temperature thermal destruction by an approved facility. Refer to your local and provincial authorities for the best potential disposal options.

9.4 Disposal of Miscellaneous Solid Wastes

Refer to Chapter A, Section 9.4 - Miscellaneous Solid Wastes for complete details.

• Make the empty container unsuitable for further use
• Do not use PCP-treated wood as a compost or mulch.
• Incineration of PCP-contaminated materials is not permitted except in facilities authorized for disposal of such products because of the formation of toxic combustion by-products

9.5 Air Emissions

Air emissions at thermal treatment facilities are generally localized; effects, if any, would be restricted to workers at the facilities. Such emissions may include the following:

• vapour from thermal tanks during the hot oil treatment process
• dust from manual unwrapping
• vapours from tank vents
• vapours from freshly treated charges

Ensure that lids from thermal treating tanks fit tightly in order to minimize the release of vapours.

Design and procedural recommendations for control of these localized emissions are suggested in Sections 7 and 8.

REFERENCE Table 23