Biomedical Engineering Reference
In-Depth Information
Starter culture:
50 gallons
grown on
nutrient broth
Colony on
agar plate
Shake flask
Pressure monitoring
at well heads
during injection
Steam-sterilized
tanks aerated
with filter-
sterilized air
Growth in filter-
sterilized
groundwater,
supplemented
with acetate,
phosphate
Figure 9.14. Steps in growth of P. stutzeri KC for use as inoculum and the inoculation during the
demonstration-scale experiment at Schoolcraft, Michigan.
9.8.3 Long-Term Maintenance of the Biocurtain
Key elements of the demonstration-scale design were enhanced delivery via recirculation,
periodic vs. continuous nutrient delivery to avoid formation clogging, and enhanced process
efficiency by creating a biodegradation/sorption treatment train within the biocurtain zone.
Improvements in chemical delivery significantly improved CT removal compared to that
achieved during the pilot-scale study (98-99% vs. 60-65%), with CT concentrations in the
demonstration scale study falling to levels less than the MCL (5 ppb) throughout the treatment
zone (Figure
9.15
) (Dybas et al.,
2002
). Chemical delivery was accomplished in two distinct
phases: a short phase (6 hours [h]) of nutrient and substrate addition through the delivery well
recirculation, followed by a much longer passive phase (~1 week) in which pumps were shut off
and contaminated water entered the treatment zone under the influence of the natural hydraulic
gradient.
During a typical chemical delivery event, groundwater was extracted from alternating (odd
or even numbered) delivery wells, circulated through the aboveground chemical addition/
mixing system, and then injected into adjacent delivery wells. Each extraction/injection cycle
(ex. odd to even wells) ended with a 1-h period of flow reversal (e.g., even to odd wells) to
ensure more uniform delivery of substrate around the initial extraction wells (the odd num-
bered wells, in this example). The 5-h pumping assignments (extraction or injection) of well sets
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