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International Journal of Environment Science and Technology
Center for Environment and Energy Research and Studies (CEERS)
ISSN: 1735-1472 EISSN: 1735-1472
Vol. 11, No. 5, 2014, pp. 1189-1196
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Bioline Code: st14116
Full paper language: English
Document type: Research Article
Document available free of charge
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International Journal of Environment Science and Technology, Vol. 11, No. 5, 2014, pp. 1189-1196
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Monitoring accelerated clogging of a model horizontal sub-surface flow constructed wetland using magnetic resonance transverse relaxation times
Bencsik, M.; Shamim, M.F.; Morris, R.H. & Newton, M.I.
Abstract
Horizontal sub-surface flow wetlands are
essentially a bed of porous material in which suitable
plants are grown to facilitate the removal of organic
matter and particulates from wastewater. The aim of
this study is to assess the reliability and accuracy of
magnetic resonance transverse relaxation time for
monitoring clogging development in a constructed
wetland. In this study, three different horizontal subsurface
flow constructed wetland models have been
produced using tubes packed with different sizes of
glass beads with diameter 3, 8 and 14 mm. Accelerated
clogging has been achieved by pumping sludge
extracted from a real clogged wetland through the
bead pack. A desktop MRI tomography system has
been used to monitor the transverse relaxation rate as
a function of position along the tube and hydraulic
conductivity. To corroborate the clogging with magnetic
resonance measurements, the head loss was
monitored to determine the hydraulic conductivity.
Using a bi-exponential fit to the spin echo train data,
the slow relaxation rate contribution shows good correlation
with the changing hydraulic conductivity.
Both fast and slow contributions map well to the
expected clog patterns for a constructed wetland. We
have demonstrated that there is a linear correlation
between the hydraulic conductivity and both parameters
of a bi-exponential fit to R2
eff, but particularly for
the case of the short T2 component.
Keywords
T2; MR relaxation time; Constructed wetland; Clogging
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