Environmental Engineering Reference
In-Depth Information
10.4.1 The BIOXWAND Technology for Ammonium Elimination
Since the 1990s, the Berlin Water Company (BWB) has been working to safe-
guard a groundwater resource with a capacity of 10,000 m³/d, which is used
for drinking water production (reference). Approximately 200 million m³ of
groundwater was contaminated with 2200 tonnes of ammonium and organic
trace cocontaminants including CHC (
cis
-DCE, vinyl chloride) and pesti-
cides as a result of waste water infiltration and drainage from an unsealed
sludge storage area of an upstream sewage field. A protection well gallery
is being used to capture the contaminated stream, and groundwater with
mean ammonium and organic trace substance concentrations of 10-20 and
0.02 mg/L respectively, are pumped out and treated at a nearby waste water
plant. The extent of the contamination of the aquifer matrix is estimated to
be 3000 tonnes of adsorbed ammonium, with approximately 2200 tonnes
accessible to treatment using ion exchange (Ehbrecht and Luckner, 2004).
After the German Federal Ministry of Education and Research funded an
evaluation of in situ cleanup approaches, the reactive gas barrier technology
BIOXWAND (EP 1550519) was chosen as the best available method for the
remediation and protection of the groundwater resource and therefore, the
best option to replace the pump-and-treat system (Figure 10.12) (reference).
Since 2007, a permeable oxygen gas barrier (length = 200 m, depth = 40 m,
thickness = 25 m) has been installed approximately 500 m upstream of the
drinking water well gallery A (Engelmann and Schmolke, 2014). The final
length of the barrier is planned to be 800 m, and it was predicted that up to
200 kg/day of ammonium will be oxidized in situ.
Based on a mass balance approach and supported by reactive trans-
port modeling (Horner et al., 2009), the initial annual oxygen demand for
the performance of a 100 m barrier segment is approximately 64 tonnes.
Approximately 28 tonnes/year of oxygen is needed to treat the inflow-
ing groundwater (20 tonnes/year for nitrification, 8 tonnes/year for iron
removal). A total of approximately 36 tonnes/year of oxygen is needed for
the partial sediment matrix treatment of 22 tonnes/year of sulphide and
14 tonnes/year of adsorbed ammonium. The total oxygen demand declined
with time due to gradual matrix oxidation.
The hydrogeology of the site is characterized by layered glacial sandy sedi-
ments to a depth of 50 m. Enclosed loamy lenses and sublayers in addition
to sand layers which have been compacted to varying amounts act as retar-
dants of the vertical gas propagation. In this way, there were four gas storage
horizons within the unconfined aquifer (Figure 10.5).
An in-line injection gallery of sealed gas lances of types BIL, DIL, RIL,
and VIL supplied the gas. The distance between the lances was 25 m and
two injection filter depths (15 m and 40 m below groundwater level) were
used. The low-pressure method (NDI) was applied, and gas injection rates
were 0.5-2.0 m³/h STP. The radii of influence (ROI) for effective horizontal
gas propagation were approximately 10-25 m. In addition to the ROI and the
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