Environmental Engineering Reference
In-Depth Information
2006 and 2012 (Birke et al., 2004, 2005; RUBIN, 2014), to address this issue in
order to achieve an improved quality assurance regarding proper practical
field scale implementations of different ZVI and NZVI brands and produc-
tion batches.
All ZVI or NZVI types, which have been applied so far to reductively
dechlorinate cVOCs in contaminated groundwater, are of technical grade,
especially regarding PRBs, which very often are made from scrap metals
of different origins, compositions, and so on. Or regarding NZVIs, which
are originally produced for application in the electronic or even food indus-
try, therefore are very often associated with different kinds and amounts
of trace elements. Thus, their reactivity regarding cVOC dehalogenation in
groundwater can vary significantly, which has already been addressed and
documented extensively (Johnson et al., 1996; Miehr et al., 2004; Ebert et al.,
2006).
We conducted long term column and short term batch experiments as
well as electrochemical investigations, to investigate the impact of differ-
ent technical ZVI brands (at nano scale as well as coarser qualities to be
used in PRBs)
as well as different ZVI production batches from the same sup-
plier
on the reductive dechlorination efficacy regarding tetrachloroethene
(PCE) in groundwater. It was found that trace elements and local surface
elements do vary significantly regarding types and amounts, and they
may have a significant impact on the degradation efficacy. It is apparent
from these investigations that a useful protocol for practical applications/
implementations is required to properly and effectively select the right
ZVI or NZVI type as well as its right production batch
just prior to
its par-
ticular field-scale application in a ZVI PRB, or regarding injecting NZVIs.
This would be especially useful when feasibility tests have been performed
significantly earlier to the actual field application, that is, wherein
different
production batches of the same ZVI type/brand might have been used/
checked earlier in the lab rather than later applied in the field. The protocol
covers instructions for recording some basic chemical and physical param-
eters (maybe repeating a column experiment, and/or just redoing some
short term, easy and inexpensive batch experiments) in order to ascertain
that the very ZVI production batch (coarse ZVI or NZVI) to be loaded to
a field-scale PRB or to be injected into a source zone, respectively, will not
significantly differ in its reactivity compared to the batch that was tested
in the column experiment earlier, thus avoiding a potential malfunction.
Such a precautionary measure may prevent applicants/stakeholders (espe-
cially, vendors and site owners) from facing a potentially serious failure
at the beginning of a field-scale application using ZVI or NZVI, simply
due to applying the “wrong” production batch. Furthermore, these inves-
tigations may deliver a significant contribution to improved planning and
help predict more precisely field-scale applications of ZVI PRBs as well as
injections of NZVIs in the future.
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