NATO/CCMS Pilot Study Evaluation of Demonstrated and ... - CLU-IN

NATO/CCMS Pilot Project on Contaminated Land and Groundwater (Phase III) January 2001
Oil refinery site. At this site in the Rotterdam Harbour area, it is required to manage a plume (>200 m up
to a depth of 4 m) of the dissolved fraction of a mineral oil/gasoline contamination (80% of the
compounds belong to the C6 - C12 fraction). The redox conditions are anaerobic and the natural
biodegradation capacity is unknown, but probably insignificant. To protect further spreading into the
harbour 3 types of bioscreens, pilot-scale sparging applications, were installed. The dimensions of each
pilot is 40 m by 0.4 m by 4 m deep. One bioscreen has been trenched and backfilled with gravel. The
other two bioscreens are vertical and horizontal air sparging fences. Results after one year is a total
biodegradation up to 70%. From 2001 the airsparging will be intensified and monitored.
Aromatic hydrocarbon (BTEX) sites. At three sites (> 250 m length and 10-80 m depth) in the northern
part of the Netherlands, deep anaerobic aquifers contaminated with Benzene, Toluene, Ethylbenzene or
Xylenes (BTEX) have been investigated. Under the existing sulphate-reducing conditions, the intrinsic
biodegradation of toluene and ethylbenzene could be demonstrated in the field and in microcosm studies.
Benzene was shown to be persistent, probably due to absence of adapted micro-organisms. Managing the
benzene plumes, i.e., by enhanced in-situ bioprocesses, is therefore required. Infiltration of electron
acceptors was investigated, for example minimal amounts of oxygen combined with nitrate. Push-pull
experiments at the site have shown complete biodegradation of BTEX. From 2001 pilot-scale application
and monitoring is planned.
Chlorinated pesticides site. Hexachlorocyclohexane (HCH) isomers are important pollutants introduced
by the production of lindane (gamma HCH). The redox conditions are mixed: sulphate reducing to iron
reducing. Natural degradation of all HCH-isomers was demonstrated at the site of investigation and in the
laboratories of TNO. To minimise all risks interception of the HCH/Chlorobenzene/benzene plume (>250
m length, up to a depth of 18 m) was needed to protect the canal located at the boundary of the industrial
site. The in situ bioremediation concept investigated at this site is integrated into new infrastructural plans
of a large transhipment facility. The semi full-scale design was constructed in 2000 and contains of 2
sequential bioscreens upstream. Here electron donor will be infiltrated and extracted and biological
biodegradation of HCH into monochlorobenzene and benzene will be monitored with monitoring filters.
Downstream an above ground (bio)reactor system is set up. Here the groundwater is extracted and
monochlorobenzene and benzene is mineralised. From 2001 testing of the complete system starts.
3. DESCRIPTION OF PROCESS
Chlorinated solvent site. Laboratory experiments identified that a mixture of electron-donors is most
suitable to enhance the in situ reductive dechlorination. In situ full-scale demonstration of enhanced
anaerobic degradation in the source zone designed for complete reductive dechlorination is currently
performed. The same technology is considered to be applied later at the head of the plume in terms of a
treatment zone.
Oil refinery site. Bench-scale experiments have been finished and established i) optimal grain-size and
packing density for the porous media used in the trench, ii) optimal oxygen supply rates to sufficiently
initiate aliphatic hydrocarbon biodegradation and to minimise clogging with iron (III) oxides. Three
different technologies are being tested at pilot scale: two gravel filled reactive trenches with biosparging
units and one biosparging fence, without excavation of the soil. Each pilot application has a length of 40
m, and a depth of 4 meters.
Aromatic hydrocarbon (BTEX) sites. Microcoms were used to investigate possibilities to stimulate
biodegradation of benzene and TEX compounds. Especially, addition of nitrate and low amounts of
oxygen to the anaerobic systems appears to be the appropriate way to create down-stream biostimulated
zones. Pilot demonstration tests are currently performed. One pilot test is a biostimulated zone with
dimensions of 10 to 10 meters.
Chlorinated pesticide site. A bioactivated zone as an alternative to conventional large-scale pump-andtreat
is currently being investigated. Laboratory process research indicated that a combination of
anaerobic-microaerophilic in-situ stimulation in a bioactivated zone is the most feasible approach.
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