Enhancement of PAHs degradation by nonionic surfactants in composting system

The effect of a nonionic surfactant, Tween 80, on the biodegradation of PAHs in acidic loamy soil spiked with 400 mg kg^-1 each of phenanthrene, anthracene, and pyrene was assessed in a bench-scale composting system. PAH-spiked soil was mixed with pig manure at a ratio of 25% (w/w dry wt). Tween 80 was applied at a rate of 20, 40, or 100 mg kg^-1 (w/w dry wt) to the composting mass at Day 0 or 14 of the composting period. Tween 80 enhanced the removal of anthracene and pyrene, whereas no significant improvement of phenanthrene removal was noted. The effect of Tween 80 on biodegradation of PAHs was also time-dependent with significantly higher degradation for treatment added at Day 14 than Day 0, especially at a Tween 80 concentration of 100 mg kg^-1. The highest removal efficiency of PAHs in the spiked soil was obtained in the treatments with Tween 80 application rate of 20 to 40 mg kg^-1 applied at Day 14 of composting process. In addition, maturation test of composting by C/N_organic and seed germination showed that addition of Tween 80. regardless of its concentration or time of addition, did not affect organic matter decomposition during the composting process. The results support the use of Tween 80 to enhance the degradation of pyrene and anthracene during composting treatment but its general use for PAH contaminated sites still requires further studies on PAHs of higher ring number.