PHYSICAL CONDITIONING TO ENHANCE BIOREMEDIATION OF EXCAVATED HYDROCARBON CONTAMINATED SOIL AT MCCLELLAN AIR-FORCE BASE

McClellan Air Force Base conducted an evaluation of an aerated-pile co mposting process and a slurry bioreactor process for biologically trea ting excavated hydrocarbon-contaminated soils while controlling emissi ons of volatile organic compounds. A large aspect of process evaluatio n was development of soil conditioning steps prior to biological treat ment. The conditioning steps evaluated were: soil washing, using tromm el and attrition scrubbers; and milling, using rod and hammer mills. S crubbing was not effective at producing a consistently clean oversize fraction. Milling was effective at reducing the size of larger materia l and breaking agglomerates. Bioremediation results indicated both pro cesses capable of greater than 90 percent reduction in hydrocarbon lev els within 90 days. Aerated-pile composting was the preferred process because it required less operation and maintenance and more easily han dled varying soil characteristics. A full-scale treatment process was developed and is described.