Case Studies

In-situ reclamation of formaldehyde-saturated railroad ballast

Submerged, fixed-film bioreactor formaldehyde-degrading bacteria and nutrients were added to assist in a in-situ bioreclamation of a formaldehyde rail spill.

Procedures and Objectives

Accidental release of 50% formaldehyde solution from a rail car (20,000  gallons) on a siding had resulted in significant rail ballast (gravel) and site soil contamination. The main body of the spill was contained by an emergency spill control contractor and residual concentrated formaldehyde solution recovered. Contaminated rail ballast and soil posed a significant problem. Removal of the formaldehyde saturated rail ballast, along with rail line reconstruction, would have resulted in significant downtime for a regularly used rail line immediately next to the site of the spill.

An in-situ spray/leach extraction system, including an aerated submerged fixed-film bioreactor, was set up to extract formaldehyde from the rail ballast without affecting the continuing operation of the rail line.


Captured leachate containing formaldehyde was pumped to an above ground tank aerated bioreactor inoculated with non-indigenous, naturally-occurring, specialized microbial strains adapted for formaldehyde degradation. Proprietary nutrients were added to enhance microbial growth and enhance removal rates. Biologically-treated water was recirculated over the contaminated ballast areas as an extraction agent.


Formaldehyde concentrations dropped from 1700 ppm to undetectable in the rail ballast over a period of two to three weeks without affecting scheduled train runs.


A significant cost savings over alternate physical disposal and/or chemical destruction methods was realized.

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