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IN-SITU VACUUM EXTRACTION PROJECTS:
9. BIOVENTING, BIOREMEDIATION AND STABILIZATION TREATABILITY STUDIES

Confidential Pharmaceutical Manufacturer, Pennsylvania

Wastewater treatment sludge and laboratory wastes had been disposed of by onsite landfilling at this major pharmaceutical research and manufacturing facility. Recent plans for significant new construction called for expansion into the disposal areas.

The owner sought alternatives to excavation and offsite disposal for the waste material still in place after the first phase of building footprint excavations. The goals of an alternative treatment would be to remove the RCRA characteristic volatile and semi-volatile compounds, to eliminate the extremely noxious odors that made the first excavation work less than pleasant, and to convert the semifluid sludge into a soil like material that would be more easily removable or could support future surface loads.

A three part treatability study was designed including: sludge stabilization, bioremediation, and bioventing. The bioventing study included field work to determine whether air flow could be induced through the fine grained material in-situ and bench work conducted over a period of 8 weeks.

Application of vacuum to the in-place waste by way of specially constructed wells showed that flow could be induced and that volatile compounds could be removed in measurable (using a photo-ionization detector) quantities. The bench work showed that significant biological activity was stimulated by drawing air through the samples. The biological activity was indicated by the measured increase in CO2 concentrations across the tested soil columns and the visually evident growth of microbial colonies. The CO2 measured entering the columns was at the atmospheric concentration of about 300 ppm while it was in excess of 6000 ppm exiting the columns during the early stages of treatment. The decline in the exiting concentrations over time showed that the aerobic bioactivity decreased as the microbes consumed the available nutrients.

The objectives of the treatability studies were to determine, for each technology, whether it could reduce the toxicity of the waste material, convert the viscous waste into a soil like material, eliminate odors, and be implemental at reasonable cost. Representative samples of the waste material were collected at the site and analyzed. Bench scale application of the treatment technologies showed that:

• ISV/Bioventing accomplished all the objectives,
• Stabilization/Solidification reduced toxicity and produced a soil like product but did not eliminate odor, and
• Bioremediation in a slurry phase reduced toxicity and eliminated odor but did not produce a soil like product and would be difficult to implement at the site.