Naphthalene Biodegradation from Non-Aqueous-Phase Liquids in Batch and Column Systems: Comparison of Biokinetic Rate Coefficients

Abstract

The kinetics of microbial degradation of naphthalene from a two-component non-aqueous-phase liquid (NAPL) coated onto uniformly sized nonporous particles were evaluated in a completely mixed batch reactor (CMBR) system and in flow-through column systems to examine the differences in the biodegradation kinetic coefficients, micro(max), the maximum specific growth rate coefficient, and K(s), the half saturation constant in the two systems. The values of these coefficients were estimated by nonlinear least-squares regression of the naphthalene mineralization profiles obtained from both CMBR and column biodegradation experiments. The results show that the range of values for micro(max) and K(s) obtained from column systems are very similar to the range of values obtained from CMBR systems. This suggests that coefficients estimated from CMBR or column systems are equally applicable for modeling studies. The presence of microorganisms and the development of biofilms at the NAPL-water interface reduced the mass transfer rates of naphthalene from the NAPL by 60% in CMBR and by 70% in column systems. If such changes in mass transfer coefficients are not accounted for, significantly erroneous values of biokinetic coefficients may be obtained.

Improved mass transfer and biodegradation rates of naphthalene particles using a novel bead mill bioreactor

“…The value of k L a at impeller rotational speeds of 200 and 400 rpm was reported to be 0.08 and 0.14 h −1 , respectively. Investigating the mass transfer of naphthalene, dissolved in silicon oil and coated as a film on the surface of 3 mm polytetrafluoroethylene beads in a completely mixed reactor, Alshafie and Ghoshal19 determined a value of 0.54 (h −1 ) for k L a ( k L = 1.15 × 10 −3 cm s −1 ). The k L a values reported here for naphthalene in the BMB are therefore similar or greater in magnitude to those that have been reported in mixed tank reactors.…”

Mass Transfer and Bioremediation of Naphthalene and Methyl Naphthalenes in Baffled and Bead Mill Bioreactors

“…The batch growth kinetics on naphthalene and 2-methylnaphthalene were simulated using fi rst order growth kinetics assuming that PAHs were the limiting substrates. First order kinetics is a reasonable assumption for the growth of P. putida on naphthalene since it has been shown that the saturation constant is considerably less than 1 mg/l (Park et al, 2001;Alshafi e and Ghoshal, 2003). However, the removal rates of the substrates (and therefore the growth rate of the bacteria) were limited by the maximum mass transfer rates of the substrates from the solid particles to the aqueous media, which differed for each type of bioreactor and each substrate.…”

Kinetic modelling of a diesel-polluted clayey soil bioremediation process

“…Furthermore, a controversial point is found in the literature concerning the availability of hydrocarbons for microorganisms. Several studies indicate that the dissolution rate from the NAPL phase determines the biodegradation rate (Alshafie and Ghoshal, 2003;Ghoshal and Luthy, 1998), because microorganisms are not able to directly consume hydrocarbons from this phase (Mukherji et al, 1998). However, other studies have proposed that microorganisms can directly access hydrocarbons in the organic-water interphase (Nakahara et al, 1977;Rosenberg et al, 1989), which led us to understand the high biodegradation rate of many hydrocarbons in the NAPL phase.…”