Wood preservation facilities, chromated copper arsenate: chapter B-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

Potential process emission sources from Chromated Copper Arsenate (CCA) Type C wood preservation facilities are described in Figure 1 and Section 5.2. The main categories of process wastes or emissions that may be encountered at CCA facilities, along with their recommended disposal methods, are presented in Table 23.

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.

9.2 Liquids Containing CCA

Liquid Process Wastes

Liquid process wastes are not normally discharged from CCA plants. Liquid solutions containing CCA, such as drips and washwaters, are routinely collected and reused in preparing new treatment solutions. If unusual circumstances (such as prolonged plant shutdown) prevent on-site reuse, transport to another CCA facility (for reuse) should be arranged. Disposal should be considered only as a last alternative.

9.3 Solids with High CCA Concentrations

Consult Section 9 of Part I, Chapter A - General Recommendations for All Wood Preservatives.

9.4 Miscellaneous Solid Wastes

CCA concentrate drums should be rinsed thoroughly (triple rinsed - see Chapter A Section 9.4) with water prior to disposal, and the rinse water should be used for the preparation of working solutions.

• Do not use CCA treated wood as a compost or mulch.
• Incineration of CCA-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 CCA facilities are normally localized; effects, if any, would be restricted to workers at the facilities. Air emissions from CCA facilities include the following:

• exhaust from tank vents
• mists from vacuum pump discharge
• mists from opening of retort cylinder doors
• mists from accelerated fixation facilities

Monitoring of mists (20, 21) in the vicinity of several CCA retort cylinder door openings has shown that, at the studied sites, arsenic, chromium and copper concentrations were below published American Conference of Governmental Industrial Hygienists (ACGIH) TLVs (22). Emissions from vacuum pump discharges have not been evaluated. However, evidence of CCA releases from such discharges was reported in an Environment Canada study (19). Some facilities discharge vacuum pumps through simple traps to condense and collect emissions (19). This practice is highly recommended. A study on air emissions from kilns treating CCA-impregnated wood indicated that releases of chromium, copper and arsenic were frequently below detection limits (25).