No abstract

A novel process for sand consolidation and sand production control tias been developed. The procedure involves the use I:)f bacteria that actively precipitate@ate calcium carbonate as a cementing agent. A series of experiments was performed in the laboratory and showed that loose unconsolidated sand is transformed into a well cemented sand. Porosity@y was reduced by up to 50% and permeability@y was reduced by up to 90% in plugging was avoided. Computer Assisted Tomography was used for the visualization of the cemented areas and the determination of the porosity distribution before

Bacteria with limited genomic cross-hybridization were isolated from soil contaminated with C5+, a mixture of hydrocarbons, and identified by partial 16S rRNA sequencing. Filters containing denatured genomic DNAs were used in a reverse sample genome probe (RSGP) procedure for analysis of the effect of an easily degradable compound (toluene) and a highly recalcitrant compound (dicyclopentadiene [DCPD]) on community composition. Hybridization with labeled total-community DNA isolated from soil exposed to toluene indicated enrichment of several Pseudomonas spp., which were subsequently found to be capable of toluene mineralization. Hybridization with labeled total-community DNA isolated from soil exposed to DCPD indicated enrichment of a Pseudomonas sp. or a Sphingomonas sp. These two bacteria appeared capable of producing oxygenated DCPD derivatives in the soil environment, but mineralization could not be shown. These results demonstrate that bacteria, which metabolize degradable or recalcitrant hydrocarbons, can be identified by the RSGP procedure.

Degradation of dicyclopentadiene (DCPD) to carbon dioxide and oxygenated intermediates was established in the laboratory. Screening of many inocula using BIOLOGMT plates showed that no single colony isolate readily mineralized DCPD. Mixed cultures from a variety of environmental sources produced 14CO2 when incubated with [14C]DCPD, but most of the DCPD was metabolized to oxygenated intermediates that could be extracted from the culture liquid and detected using gas chromatography and mass spectroscopy. Stimulation of environmental inocula with nutrients and preexposure to DCPD before testing for degradation gave mineralization rates after 25 days of in vitro incubation that were twice as fast as those previously reported.