Wood preservation facilities, general recommendations: chapter A-9


9. Waste, Process Emissions and Disposal

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The preservation of wood in treatment facilities generates liquid and solid wastes and may also produce emissions to the air. Wastes may include wood debris (treated or untreated), used filters, wraps, solution precipitates; and sludge removed from sumps, cylinders, tanks and containment areas. Other wastes include sludge from wastewater treatment processes (e.g. flocculated material) and contaminated soils. Waste minimization such as recovering and reusing preservatives should be practised to the utmost to reduce the amount of waste generated at the facility.

This section provides general recommendations on the techniques to minimize the amount of chemicals to be released from the wood preservation facility. There are numerous approaches available for control, treatment and disposal of process wastes and emissions. Due to the specific characteristics of the various preservatives, designs and operating procedures for pressure or thermal facilities, the issues are generally specific to individual facilities. Table 23 details all of the applicable recommendations for handling liquid and solid wastes and sludge.

Post-use treated wood is not directly addressed in the TRD. A provisional code of practice for the management of post-use treated wood has been prepared by the Hazardous Waste Task Group of the Canadian Council of Ministers of the Environment (CCME) (11, 13).

9.1 Control, Treatment and Disposal

The facility pollution prevention plan should include practices to reduce the amount of solid and liquid wastes to be controlled, treated and/or disposed. Such practices can be developed with the help of a specialised process engineer or consultant since each facility has their own challenges.

For wastes that require control, treatment or disposal, the process used will generally be regulated by provincial jurisdiction and may vary from province to province. Potential practices for waste disposal may include incineration, recycling, transfer and final disposal in landfill at facilities that have an appropriate license.

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

9.2 Liquids Containing Preservative

Contaminated Storm Runoff

Contaminated storm runoff should be minimized. Various approaches can be used, including ensuring a proper final vacuum to remove any excess solution from treated wood; use of roofed areas for treated product storage; ensuring proper fixation methods and minimization of surface deposits (by keeping solutions clean) prior to storage in the open environment; and containment and reuse of storm runoff waters. In areas of high rainfall, complete containment may not be economically feasible and roofing might be preferred. Refer to Section 7 for the recommendations on design features that minimize storm runoff.

If the release of contaminated runoff is required, specific approvals must be obtained from the appropriate provincial or municipal environmental regulatory agency. Control specifications may depend on factors such as the volume and frequency of the discharge and the sensitivity of the receiving environment. The discharge of some contaminated runoff into waters inhabited by fish might be subject to the provisions of the federal Fisheries Act (14).

Liquid Process Wastes

On-site reuse, transport to another facility for reuse and treatment of contaminated liquid are ways to avoid disposal of liquid solution such as drips and wash water.

If the contaminated liquid is to be treated on-site, the facility may be required to meet certain conditions set out by the municipal, provincial and/or federal requirements. Some treatment techniques that are available include the following:

  • gravity separation
  • plate separation
  • activated carbon treatment
  • flocculation
  • evaporation/condensation

A regulatory discharge permit must be obtained for disposal of the treated aqueous wastes and the conditions governing the discharge must be met.

If off-site disposal is unavoidable, specific approval must be obtained from the appropriate regulatory agency. If no suitable means of disposal are readily available, the solutions should be sealed in leak-proof containers, labelled and stored in a secure area in accordance with WHMIS requirements as well as other conditions that are set out by the provincial and/or municipal jurisdiction.

9.3 Solids with High Preservative Concentrations

For the purposes of this document, solids with “high preservative concentrations” include:

  • recuperated spill material;
  • sludge from sumps, tank and cylinders;
  • sludge from wastewater treatment processes (e.g. flocculated material);
  • cartridge filters used to filter recycled waters;
  • “spent” activated carbon; and
  • solid chemical dust from vacuum recuperation.

Recovery of the components (e.g. active chemicals) represents an ideal option but is rarely available for facilities. The current practices and requirements for the disposal for these solids with high preservative concentrated should be acquired from your local jurisdiction. In addition, refer to your provincial and municipal offices for more information. It is the responsibility of the waste generator to obtain and to comply with the conditions required by the appropriate jurisdiction(s).

Solids with high concentrations of preservative might need to be drained and stored in leak-proof, sealed and labelled containers while awaiting disposal. Contaminated solids should be stored in a specifically designated area that is curbed and lined with impermeable material. The area should be roofed to protect the wastes from precipitation. Refer to Table 11 for more details on design recommendation for storing area.

9.4 Miscellaneous Solid Wastes

Miscellaneous solid wastes (e.g. empty concentrate drums, wrappings, stickers or cuttings/broken pieces from treated lumber, contaminated sawdust or debris and empty pallets) from wood preservative facilities may be disposed of at designated sanitary landfills as approved by the provincial regulatory agency.

Containers should be clean before final disposal unless otherwise specified by the recuperation company. Suggested procedure to clean containers of water-borne preservative before final disposal:

  1. fill container about 10% full with water;
  2. agitate container vigorously;
  3. discard rinsate according to pesticide disposal instructions;
  4. repeat this rinsing procedure two more times.

For oil-borne preservatives or additives, it may be required that containers be steam-cleaned prior to disposal. Make empty non-reusable container unsuitable for further use. Follow provincial regulatory requirements for any required additional cleaning and disposal of the container.

For additional information on disposal of unused, unwanted product, contact the manufacturer or the provincial regulatory agency.

9.5 Air Emissions

Air emissions from process operations at many facilities are localized; effects, if any, would mostly be restricted to workers at the facilities. Ventilation and/or use of specific PPE or protective measures should be in place for high-risk work stations (e.g. enclosed areas) and/or where frequent exposure may occur. An overall good air flow within the plant should be maintained. When possible, process controls (e.g. scrubbers, extraction fans) should be used to control releases from plant equipment.

Source of emissions may include:

  • Vapours/mist from tank vent;
  • Vapours/mist from opening of retort cylinder doors;
  • Vapours/mist from freshly treated charges; and
  • Vapours/mist from vacuum system outlets.

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