Use of calcium peroxide to provide oxygen for contaminant biodegradation in a saturated soil

Laboratory studies were conducted in solid-phase reactors on a silty loam contaminated with bis-(2-ethylhexyl) phthalate (BEHP) to determine the conditions under which calcium peroxide (CaO2) would promote the aerobic bioremediation of water-saturated soil. Closed 500 ml solid-phase reactors were operated to determine whether CaO2 stimulated the biodegradation of BEHP in saturated soil. Ex situ bioremediation conditions were then simulated by mixing water-saturated soil for 6 h before placing the soil in three vented, 2 1 solid-phase reactors for 50 days. Biodegradation of BEHP was quantified using four different measurements of microbial activity: (1) oxygen concentrations in the reactor gas; (2) bacterial colony-forming units (CFU); (3) fungal CFU; and (4) 2-(p-iodophenyl)-3-( p-nitrophenyl)-5-phenyl tetrazolium chloride dehydrogenase activity (INT-DHA). CaO2 released molecular O-2, which retarded dewatering but substantially enhanced BEHP biodegradation. After 20 days, BEHP in the amended reactor was reduced from 20.3 to roughly 5 g kg(-1) vs. 15 g kg(-1) in the reactor without CaO2. Bacterial growth was favored over fungal growth at elevated moisture and BEHP levels. (C) 1999 Elsevier Science B.V. All rights reserved.