BENCH-SCALE EVALUATION OF BIOAUGMENTATION TO REMEDIATE CARBON TETRACHLORIDE-CONTAMINATED AQUIFER MATERIALS

Pseudomonas sp, strain KC is a denitrifying bacterium that, under iron -limited conditions and in the presence of sufficient quantities of gr owth substrate, rapidly transforms carbon tetrachloride (CCl4) to carb on dioxide and nonvolatile products without production of chloroform, Bench-scale laboratory methods were used to evaluate the feasibility o f bioaugmentation with strain KC to remediate aquifer materials from a n aquifer of documented CCl4 contamination at Schoolcraft, Michigan. N ine glass columns packed with uncontaminated aquifer materials from th e site were used to simulate aquifer conditions, Columns were alternat ely exchanged with ground water from the site in a rapid (20-30 minute ) displacement of the pore fluid, then incubated under static conditio ns for a period of days to weeks, The exchange and incubation procedur e continued until CCl4 removal began to plateau, indicating equilibrat ion of the sorbed CCl4 with CCl4 in the pore fluid, Information obtain ed during this period was used to evaluate porosity (total and effecti ve) and CCl4 sorption, In subsequent exchanges, base, acetate, and pho sphorus were added to the exchange fluids to create conditions favorab le for growth of strain KC and expression of its CCl4 transformation a ctivity (niche adjustment). Three columns were inoculated with strain KC; three were not inoculated; and three were chemically disinfected w ith thimersol. Strain KC was transported more rapidly than the average linear velocity of the exchange fluids in the inoculated columns, Pro tein levels measured in the effluent of the inoculated columns during subsequent exchanges indicated that niche adjustment enabled rapid gro wth and colonization of the aquifer solids by strain KC. Little or no protein was detected in the effluent of uninoculated columns. CCl4 mas s balances on the inoculated, noninoculated, and chemically disinfecte d columns indicated that niche adjustment and inoculation with strain KC created conditions favorable for CCl4 removal from the aquifer soli ds, Up to 70% removal of soluble CCl4 (30-50 mu g/l) occurred in inocu lated columns over a period of seven to nine days.