Water Research 38 (2004) 2027–2034 Mass transfer and bioremediation of naphthalene particles in a roller bioreactor I. Sulistiyati Purwaningsih a , Gordon A Hill a, *, John V Headley b a Department of Chemical Engineering, Research Annex, 105 Maintenance Road, University of Saskatchewan, Saskatoon, Canada SK S7N 5C5 b National Water Research Institute, Environment Canada, 11 Innovation Blvd, Saskatoon, Canada SK S7N 3H5 Received 7 March 2003; received in revised form 16 September 2003; accepted 27 January 2004 Abstract 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 50RPM. 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-b-cyclodextrin (a solubility enhancer) failed to improve naphthalene slurry bioremediation. In order to successfully bioremediate naphthalene particles at concentrations over 300mg/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 1000mg/L and at rates up to 10mg/Lh. r 2004 Elsevier Ltd. All rights reserved. Keywords: Naphthalene; Particle mass transfer; Bioremediation; Roller bioreactor; Modelling 1. Introduction and background Naphthalene is the simplest and most biodegradeable PAH compound consisting of two fused aromatic rings. Naphthalene is manufactured in North America as either an intermediate or commodity chemical at a rate of 175,000 ton per year [1]. Being the simplest PAH compound, it is also abundantly found due to natural degradation processes of more complex PAH com- pounds found in crude oils, tars and coke. It is the most soluble PAH molecule, about 30mg/L in water, and can be found adsorbed to soils and in solution in wetlands contaminated by industrial or transportation spills [2] where it has been observed to persist for decades. It is a priority pollutant CEPA [3] because of its known toxicity to higher forms of life NIOSH [4]. Pseudomonas putida can readily metabolize naphthalene beginning with a dioxygenase-mediated reaction to form cis- naphthalene dihydrodiol and eventually catechol [5]. Although several publications have focused on the metabolic pathways of naphthalene degradation and more recently on the bioremediation of naphthalene adsorbed to soil, in PAH mixtures and by microbial mixtures, very little information is available on the pure biokinetics of naphthalene particle degradation in a water slurry. Manohar and Karegoudar [6] experimen- tally demonstrated that free cells of Pseudomonas could completely degrade 3200 mg/L naphthalene in 3 days (44mg/Lh) and if these cells were immobilized in alginate, agar or polyacrylamide, this operation could be repeated in fed batch cycles. Guha et al. [7] investigated the biokinetics of pure, soluble naphthalene ARTICLE IN PRESS *Corresponding author. Tel.: +1-306-966-4765; fax: +1- 306-966-4777. E-mail address: gah548@engr.usask.ca (G.A. Hill). 0043-1354/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2004.01.035