Environmental Engineering Reference
In-Depth Information
conductivity two orders of magnitude lower than the predicted value. This
can be ascribed to biofouling and/or accumulation of methane inside the
iron filings. This experience suggests that when biopolymer shoring is used,
long-term column tests should be performed beforehand with initial bacte-
rial inoculation and organic substrate dosing, to predict the effects of bac-
terial overgrowth and gas generation. During construction, particular care
should be taken to minimize the amount of biopolymer used so that com-
plete breakdown can be achieved (Zolla et al., 2009).
13.6 PRB Site in Czech Republic
13.6.1 Pardubice, East Bohemia
Set up in 2003; a pilot-scale, T&G system, in situ bioreactor, oxyhumolite (oxi-
dized young lignite), various organic pollutants up to 30 mg/L BTEX, chloro-
benzenes, naphthalene, nitro-derivatives, phenols, TCE, and total petroleum
hydrocarbon (TPH) (Parbs and Birke, 2005; Vesela et al., 2006).
The concept of a biofiltration-permeable barrier was tested in the labora-
tory and in pilot scale. Oxyhumolite was used as an absorption material and
biofilm carrier. During laboratory biofiltration experiments, it was estab-
lished that naturally occurring microflora derived from contaminated water
of the model pilot site had become adapted to local conditions and that it was
possible to increase their activity by adding N and P nutrients. Laboratory
column tests confirmed that a retention time of 15 h was sufficient for a 97%
reduction of all contaminants in the groundwater (with the exception of
poorly degradable substances such as nitrobenzene or N,N-diethylaniline),
provided that other conditions (mainly oxygen and nutrient concentrations)
were optimized. Two bacterial species were isolated from this contaminated
groundwater. They were identified to be nitrate reducers, and some strains
being able to fix nitrogen (Vesela et al., 2006).
Prior to installation, preliminary investigations of the unsaturated zone
(boring up to 2.0 m, sampling) and saturated zone (drilling of five wells,
pumping tests including sampling) were performed. The site consists of
sand and sandy gravel-fluvial deposits of the Elbe River up to 2.5 m thick
(Vesela et al., 2006). The aquifer is underlain by impermeable clays. On the
basis of this investigation, the pilot biobarrier was designed as a T&G (D&G).
The system consisted of a single-drainage trench, installed perpendicu-
lar to the groundwater flow, which carried contaminated groundwater to
an underground bioreactor/gate (Parbs and Birke, 2005). It was approx. 13 m
long and 1.0-1.5 m wide, and it was keyed into the underlying imperme-
able clay (2.6-3.0 m below the ground). The bottom of the trench was sealed
with a plastic liner; above, it was filled with permeable gravel and native
Search WWH ::
Custom Search