Mass transfer and bioremediation of solid polycyclic aromatic hydrocarbon (PAH) particles in bioreactors.

摘要

Information about mass transfer behaviour of solid PAHs particles, which were carried out in both a well-mixed bioreactor and a roller bioreactor, has been gathered prior to commencing the bioremediation studies. The dissolution rate of PAHs particle into the aqueous phase is significantly affected by the particle concentration and ultimate solubility. The air stripping coefficient is highly dependent on both air flow rate and temperature. The dissolution rate of naphthalene particles was much slower and the air stripping parameter was much lower in the roller bioreactor than that in the well-mixed bioreactor.; Batch studies of bioremediation of solid PAHs particles were carried out in the roller reactor using a pure culture of Pseudomonas putida ATCC 17484. Preliminary investigation demonstrated that phenanthrene cannot be utilized by these bacteria, so that further experiments were focused on bioremediation of solid naphthalene particles only. Catechol was detected as an inhibitory product accumulated in the broth solution. The maximum catechol concentration that the bacteria could tolerate was determined to be 400 mg L-1. It was observed that at naphthalene particle concentrations above 500 mg L-1, bioremediation of naphthalene particles in the roller bioreactor was highly dependent on the dissolved oxygen availability. No enhancement of degradation rate was detected by the presence of glucose as co-substrate in the media, which was simultaneously utilized by the bacteria. Introducing hydroxypropyl-beta-cyclodextrin (HPCD) to the media was dramatically enhanced naphthalene solubility, but did not increase the depletion rate due to the competitive utilization between naphthalene and propylene glycol (impurity from HPCD).; To predict the depletion rate of naphthalene particle, mechanistic mathematic models have been developed. For kinetic growth on naphthalene as the sole substrate, the model was based on the Monod equation generalized to account for the effect of product inhibition. For the condition in which both naphthalene and glucose were present in the media, the kinetic model was expanded by incorporating the Monod equation to account for growth on glucose, and the generalized Monod model to account for naphthalene and product inhibition. Over the concentration range used in this investigation, the mechanistic model fit the experimental data quite well.