The biodegradation experiments using naphthalene and phenanthrene were performed in 500 ml flasks on a rotary shaker (150 rpm). The PAHs in the aqueous phase were prepared using the same method as for the solubility experiment. The flasks had various concentrations (2, 1, 0.5, and 0.25 g/l) of surfactants and PAHs (naphthalene and phenanthrene), and were shaken for 48 h at 20°C on a rotary shaker (125 rpm). The solutions were then filtered to separate the crystalline portion of the PAHs. The solutions were immediately added to the NMB solution, which contained micro-organisms acclimatised to phenanthrene, in order to prevent the loss of PAHs from volatilization. The reaction solution was sampled at set time intervals and the samples were filtered through 0.2 μm filter paper. The filtered solution was analyzed for naphthalene and phenanthrene using HPLC.