QXR-W
Wood Products Sorter / Separator
Separate
Toxic CCA treated Wood from Non-CCA Treated Wood
Introduction
to Treated Wood Disposal & Recycling
Chemical treatments of wood are beneficial
to extending its serviceable life and can be credited with
facilitating the industrial development of many countries,
providing products requiring little maintenance in aquatic
environments and when exposed to harsh weather conditions.
They have also helped to preserve forest resources by lessening
the demand for replacement wood for decaying or demolished
structures. Though significant benefits can be tied to treated
wood materials, the highly popular CCA product is being
pulled from store shelves in light of new scientific evidence
of its potential cancer causing effects of one of its key
ingredients, arsenic (As). While this action reduces the
amount of CCA treated wood created, it doesn't reduce the
amount of treated wood entering disposal streams in the
near future or the harm it potentially creates. Common disposal
routes for waste wood include recycling into composite materials
and mulch, incineration for fuel generation, and land-filling.
Unless the treated wood is identified and removed prior
to disposal, the CCA chemicals can re-enter the domestic
markets, or harm the environment through entering air and
water supplies.
Historical
Overview
Treated wood products came into use in the
1880s primarily for use in industrial applications. It was
only recently in the 1970s that CCA products became popular
for domestic use. When it represented only a small portion
of the waste stream, there was little end of life disposal
concerns. It was disposed of by normal channels, heading
to recycling facilities for reuse, to incinerators for fuel
generation, or land-filled. The dilution effect of being
combined with a large majority of untreated wood material
minimized its effects, however, with a serviceable life
of approximately 20 to 25 years, this is no longer the case.
It is an increasing portion of wood waste recovered by demolition
and deconstruction facilities. In 2002, over 8 million cubic
meters of CCA treated wood was disposed of. By the year
2020, this will have increased to approximately 20 million
cubic meters.
Sample configuration of a
QXR-W Sorter.
Click here
for larger view.
Health
Effects & Entry Points
The main concern for CCA treated products
is caused by the arsenic (As) present in the treatment solution,
retained in large amounts by the wood. The chemicals may
be ingested through hand to mouth contact, raising the risk
of a person developing cancer. Of most concern are children
in close contact with CCA treated playground equipment.
Additionally, the chemicals may be released into the air
supply as As2O5 when burned and remain in the residual ash;
or may leach from the wood into the water supply if the
landfill is unlined..
Legislation
& Restrictions
Starting in 2003, CCA chemical providers
voluntarily agree to limit manufacture of CCA products to
industrial applications (marine/aquatic uses, railroad ties...),
and have developed several other non-hazardous replacement
products for use in the domestic market (decks, playground
facilities, landscaping...). Remaining CCA product should
be off store shelves by 2004.
CCA
Identification & Removal
Stains and test kits are suitable for single
test applications, but are too labor intensive and slow
for mass recycling operations. For these facilities, and
energy-dispersive X-ray fluorescence (EDXRF) spectrometer
is more appropriate. These instruments have the ability
to detect the chemical components of CCA treated wood quickly
with little or no sample preparation. The instruments use
X-rays to stimulate elemental fluorescence of wood. The
presence of arsenic, copper and chrome fluorescence indicates
treated wood is present.
The Austin AI QXR-W is an automated EDXRF
spectrometer designed to perform positive material identification
of CCA treated wood for high volume facilities. The measurement
is performed as materials move on a conveyor belt. Positive
identification of CCA product initiates a signal for diversion
of that material from the main stream. The remaining materials
continue on a set of conveyors to a collection or processing
point. Using this automated system, 10 tons per hour of
material can be processed. Higher volume throughput can
be achieved through tandem mounted systems. The QXR-W is
not hampered by dirty and/or wet wood, and may also be configured
to separate a variety of tramp metals, should the waste
stream not be completely free of debris. Large surface nails
may also be detected.
If a small volume of wood is to be analyzed,
a portable instrument may be used to positively identify
the presence of the CCA solution and segregated by hand.
Integration
The
QXR can be integrated into facilities at most any point
of bulk conveyance of material. However, it is important
that the integration occur before significant size reduction
occurs. This will allow for the maximum number of quality
measurements performed by the system and improve accuracy
of the separation. It will also help present the material
to the analysis system in a single flat layer to further
ensure the ease and accuracy of product separation.
