Environmental Engineering Reference
In-Depth Information
TABLE 10.2
Algorithm for Optimization of the Performance of Gas PRBs
Performance
Limitations
Risk Lowering
Measures
Optimization Actions
Distribution of
reactants
Refining the injection
array density by gas
analysis-hydro geo-
logical model
Horizontal ROI dimensions and overlapping
Injection gallery sequences in flow direction
Identification of gas retardants
Injection below treatment layer
Variation of the injection
rate and pulses
Injection rate (NDI) or pressure (HDI) change
Pulse frequency change
HDI-NDI combination
Use of carrier gases
Hydraulic autoregulation by nitrogen clogging
Short-term reloading of reactants (e.g., oxygen)
Gas mixture supply (e.g., trace gases,
methane-air)
Use of a downstream
reaction zone
Macrodispersion mixing of reactants
Amplification of reaction length and time
Gas
dissolution
Forcing gas supply to
fine to medium
grained sediments
Formation of dense gas networks with high
mass transfer interfaces
Homogenization of gas distribution
Limiting gas supply to
coarse sediments and
capture zones
Prevention of inactive gas capture zones
Dissolved
concentration
range of
reactants
Limiting reactant
concentrations
Lowering gas saturation
Partial pressure variation of reactants
Optimization of the
geochemical state
Aerosol or foam injection to control, e.g., pH,
Hardness and cometabolic degradation
Supply of higher oxidizers (e.g., H
2
O
2
)
Nutrient supply
Supply of gaseous and solid nutrients
(e.g., CH
4
, CO
2
, phosphate)
Clogging,
permeability
losses
Periodical redox state
changes (aerobic/
anaerobic)
Lowering the injection cycle time
Increasing break periods
Avoiding the carrier gas supply
Demand-oriented reactant supply
Bypassing of
groundwater
flow
Forcing autoregulation
Hydraulic forcing of bulk groundwater flow
due to local pumping or drainage
Source:
Internal document of Sensatec GmbH, Kiel. With permission.
aerobic enhancement of biodegradation. The third example is an in situ drain
and gate technology (GFIadags
®
) which included two RGBZs as a treatment
train for a plume of a complex inorganic and organic contaminant contain-
ing ammonium, phenols, aromatics, DOC). A zone for the removal of iron by
oxygen and ammonia gas and a polishing downstream oxygen gas reactor
for the degradation of ammonium and DOC were formed.
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