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Resistance and treatment capacity of four macrophytes species to leachate with
wood preservatives
E. Demers, J. Vincent, J. Brisson
Institut de Recherche en Biologie Végétale, Département de sciences biologiques, Université de
Montréal. 4101 East, Sherbrooke St, Montreal (Quebec), H1X 2B2 CANADA.
Introduction
Pentachlorophenol (PCP) and chromated copper arsenate (CCA) are two wood
preservatives currently used around the world to treat wood poles from deterioration. The
treated wood poles are usually stored in wood pole yards and are exposed to weather
condition. Snowmelt and rainfall percolating through woodpiles will leach chemicals and
wood preservatives from the wood. This leachate is often characterised by the presence of
heavy metals (chromium, copper and arsenate), chlorophenols, dioxins and furans (Chang
et al.
2013, Crosby 1981). Theses pollutants are toxic and the contaminated leachate has to
be collected and treated before being released in the environment. Constructed wetlands is a
low cost, environment friendly technology that can treat a wide range of organics and
inorganics pollutants (Vymazal 2009). However, its efficiency in treating leachate from
wood pole yards remains to be demonstrated. The choice of plant species may influence the
removal efficiency of constructed wetlands (Brisson and Chazarenc 2009). A wide range of
species are used, but
Phragmites australi
s is the most common macrophyte species in CW
system (Brix 1994). In North America, the Eurasian subspecies of
Phragmites australis
(
P.
australis australis
) is invasive, so its use in constructed wetland is not recommended and
occasionally prohibited. There is North American native subspecies of
P. australis
(
P.
australis americanus
) but its capacity in constructed wetlands has not been tested so far.
This study is part of a project that aims to evaluate the feasibility of treating a leachate
contaminated with PCP and CCA on constructed wetlands.
We tested the resistance and treament capacity of 4 macrophyte species (
Typha
angustifolia, Phalaris arundinacea
,
P. australis americanus and P. australis australis
) to
leachate containing PCP, CCA, dioxin and furan.
Methods
Experimental set-up.
Research was conducted at a wood pole yard site near Montreal
(Québec) Canada. We conducted a pilot-scale experiment to test removal efficiency under
real situation, and a pot experiment offering a better control on pollutant concentration.
Four pilot-scale HSSF of 7m
2
were built, planted with
Phragmites australis australis,
Phragmites australis americanus, Phalaris arundinaceae
and
Typha angustifolia
in
monocultures, and operated in summer 2012 and 2013 (Figure 1). The wetlands were
fed directly with the leachate that came from the pole yard site. The influent discharge for
each pilot is 125 L J
-1
with a hydraulic retention time of the void (HRTv) of 19.5 days.
