Monod Kinetics for Aerobic Biodegradation of Petroleum Hydrocarbons in Unsaturated Soil Microcosms

Abstract

We use Monod kinetics to calibrate previously published data that documentthe aerobic biodegradation of hydrocarbon vapors in soil microcosms from a weathered petroleum spill site. Monod kinetics offer insight into biodegradation mechanics because they address biomass growth as well as substrate depletion. A blend of five aromatics and five alkanes dose the microcosm sets at four strengths, and a finite difference model describes the response superimposed across the constituent substrates. An observed initial biomass X0 of 125 g biomass/m(3) soil moisture and an endogendous decay rate b of 0.102 day(-1) calibrate all four dosages and agree with heterotrophic plate counts. Common maximum specific growth rates microMJ and half saturation constants KSJ calibrate each constituent across the four dosages. The biodegradable alkanes exhibit microMJ values ranging from 0.0190 to 0.0996 day(-1), while the aromatic rates vary from 0.0946 to 0.322 day(-1). One of the alkanes (2,2,4-trimethylpentane) is recalcitrant. The half saturation constants range from 0.000083 to 0.000355 g substrate/m(3) soil moisture for the biodegradable alkanes, which imply zero-order kinetics. The aromatic KSJ values vary from 5.02 to 14.3 g substrate/m(3) soil moisture, and suggest first-order kinetics. The yield YJ increases with dosage concentration for all the biodegradable constituents, varying from 0.0533 to 1.58 g biomass/g substrate.

Experimental Results and Integrated Modeling of Bacterial Growth on an Insoluble Hydrophobic Substrate (Phenanthrene)

“…38 The yields of 0.21 g biomass g substrate −1 observed are in the range of values observed for other aromatic hydrocarbons. 38 Other Model Approaches.…”

Biosurfactant from Pseudomonas species with waxes as carbon source – Their production, modeling and properties

“…The maximum growth rate of P. aeruginosa with n-hexadecane and neicosane were 0.175 and 0.08 h À1 , respectively, while the corresponding growth rate with P. fluorescens were 0.1 and 0.16 h À1 , respectively. Ostendorf et al [25] observed the maximum growth rate of 0.09 d À1 with heneicosane using Acinetobacter, whereas Table 1 Comparison of microbial growth rate with degradation of paraffin and production of rhamnolipid at 40 h of incubation.…”

“…Two types of model can be used for kinetic studies, namely, Monod and Logistic model. Many studies have been performed on the microbial growth and kinetics of degradation of hydrocarbons using the Monod growth model [18,25]. The Monod model involves the concept of growth limiting substrate.…”

Review of Microbial Processes in the Near-Surface Environment and Their Implications for the Chemical Fingerprinting of Hydrocarbon Fuels

“…This application is further enhanced by the published results of laboratory experiments that demonstrated a linear decrease in concentration of n-alkanes with the time of fuel incubation under aerobic conditions. The observed linear depletion of n-nonane and n-decane during hydrocarbon biodegradation in aerobic soil microcosms from a petroleum spill site was interpreted as indicating that microorganisms degrade the alkanes on a zero-order basis, whereas degradation of aromatic hydrocarbons follows first-order kinetics (Ostendorf et al, 2007). A broader range of n-alkanes was investigated in laboratory experiments on effects of aerobic biodegradation of North Sea crude oil on hydrogen isotopic composition of hydrocarbons (Pond et al, 2002).…”