Mass transfer and bioremediation of naphthalene particles in a roller bioreactor

Naphthalene particles in a water slurry have been bioremediated in a sealed, roller bioreactor using a pure strain of Pseudomonas putida. High stripping losses of particles due to both splashing and aeration made the use of the traditional CSTR bioreactor unsuitable for bioremediation of naphthalene particles. The overall dissolution mass transfer coefficient of naphthalene particles in the roller bioreactor was low, 0.055 h(-1) at 50 RPM. The dissolution mass transfer rate was the limiting step for bioremediation. Although mass transfer was identified as the rate limiting step, the addition of hydroxypropyl-beta-cyclodextrin (a solubility enhancer) failed to improve naphthalene slurry bioremediation. In order to successfully bioremediate naphthalene particles at concentrations over 300 mg/L, intermittent aeration was applied in the sealed roller bioreactor on a daily basis. By operating in sequential batch mode with intermittent aeration, the roller bioreactor was successfully used to continuously bioremediate naphthalene particles at concentrations up to 1000 mg/L and at rates up to 10 mg/Lh.