DEGRADATION OF XENOBIOTIC COMPOUNDS IN-SITU - CAPABILITIES AND LIMITS

Exploiting microorganisms for remediation of waste sites is a promisin g alternative to groundwater pumping and above ground treatment. The o bjective of in situ bioremediation is to stimulate the growth of indig enous or introduced microorganisms in regions of subsurface contaminat ion, and thus to provide direct contact between microorganisms and the dissolved and sorbed contaminants for biotransformation. Subsurface m icroorganisms detected at a former manufactured gas plant site contami nated with coal tars mineralized significant amounts of naphthalene (8 -43%) and phenanthrene (3-31%) in sediment-water microcosms incubated for 4 weeks under aerobic conditions. Evidence was obtained for naphth alene mineralization (8-13%) in the absence of oxygen in field samples . These data suggest that biodegradation of these compounds is occurri ng at the site, and the prospects are good for enhancing this biodegra dation. Additional batch studies demonstrated that sorption of naphtha lene onto aquifer materials reduced the extent and rate of biodegradat ion, indicating that desorption rate was controlling the biodegradatio n performance.