Environmental Engineering Reference
In-Depth Information
same value. If the batch experiment is repeated again using the actual (dif-
fering) production batch of ZVI or NZVI to be charged into a field-scale PRB
or to be injected into an aquifer, respectively, and it shows nearly the same
value of k(obs), there would be no concern to actually apply it in the field.
If k(obs) were significantly lower, one should be cautious regarding apply-
ing this production batch to the PRB in the field. Further investigations are
required. In parallel or as a stand-alone solution, an electrochemical deter-
mination of the surface-dependent first-order rate constants k
SA
, as outlined
in Figures 5.5 and 5.6, is also a very good approach to check the ZVI or NZVI
production batch for its proper reactivity towards cVOCs shortly before its
field application.
In addition to checking k(obs) in a simple batch experiment or k
SA
in the
electrochemical batch experiment, it could be useful to perform some fur-
ther simple analyses, especially for ZVI brands produced from iron scrap,
according to a test protocol of Connelly-GPM Inc., Chicago, Illinois (USA)
(Klein, 2007; personal communication by the owner of Connelly-GPM Inc.,
Mr Stephen M. Klein, with the first author (VB) in October 2007):
• Raw borings are tested for moisture content by weight difference
with oven drying.
• Borings sample is tested for oil content by weight difference with
flame heating.
• Nonferrous content determined both by magnetic separation and
caustic bath.
• Sample is screened to determine particle size distribution.
• Sample is ground to simulate effects of processing, then screened to
estimate postmill particle size distribution.
• Based on a combination of the results of the above test protocol, a
decision is made regarding the suitability of the raw material for
ZVI production.
• After approval, all subsequent shipments are inspected to confirm
uniformity with the approved sample.
• Borings are kept in 9-12 separate piles for proprietary blending.
• The density is checked by filling a box with product and determin-
ing the total weight.
• In the case of 3000 lbs bulk bags, samples are taken from each bag
and marked “top,” “middle,” or “bottom” and labeled with the pro-
duction code designation, so that it can be matched to the bag. These
three samples are tested for water absorbency, and combined with
a maximum of nine bulk bags and a screen test run. Also, there is a
visual inspection of the three samples for uniformity. Any change in
appearance at the beginning and at the end is noted. This is taken
into consideration when samples are grouped for further testing.
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