Effects of mixing low amounts of orange peel (Citrus reticulata) with hydrocarbon-contaminated soil in solid culture to promote remediation.

The effect of mixing low amounts of orange peel (Citrus reticulata) with a soil contaminated with hydrocarbons (58,000 mg kg(-1) soil) for promoting the soil remediation in solid culture was studied. The experimental design was established in solid culture at soil/orange (Citrus reticulata) peel ratios of 100:0, 98:2, 96:4, 94:6 and 92:8, at 30% humidity and a C:N:P ratio of 100:10:1, for 15, 60 and 90 days, respectively. The total petroleum hydrocarbons (TPHs) decreased significantly (69%) after 15 days in the treatment with a soil to orange peel ratio of 92:8. Furthermore, in this treatment bacterial counts increased from 17 to 20 ln CFU (2.6 x 10(6) to 5 x 10(8)), while the fungal count was 11 ln CFU (6.5 x 10(4)) at initial and final time of treatment. An increase in microbial respiration activity and TPH removal (69%) was observed at other soil/orange peel ratios after 60 days when moisture content and nutrients were adjusted; however, N and P were not consumed at a great extent.