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Schirmer, Mario

Nom
Schirmer, Mario
Affiliation principale
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Ancien.ne collaborateur.trice
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https://libra.unine.ch/handle/123456789/163

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  • Publication
    Métadonnées seulement
    Modeling the impact of ethanol on the persistence of benzene in gasoline-contaminated groundwater
    (2002)
    Molson, John W
    ;
    Barker, James F
    ;
    Frind, Emil O
    ;
    Schirmer, Mario 
    [1] The effect of ethanol on the persistence of benzene in gasoline-contaminated aquifers is simulated using a multicomponent reactive transport model. The conceptual model includes a residual gasoline source which is dissolving at the water table into an aquifer containing a limited amount of dissolved oxygen. The coupled processes include nonaqueous phase liquid (NAPL) source dissolution, transport of the dissolved components, and competitive aerobic biodegradation. Comparisons are made between dissolved benzene plumes from a gasoline spill and those from an otherwise equivalent spill containing 10% ethanol (gasohol). Simulations have shown that under some conditions a 10% ethanol component in gasoline can extend the travel distance of a benzene plume by up to 150% relative to that from an equivalent ethanol-free gasoline spill. The increase occurs because ethanol preferentially consumes oxygen, which reduces the biodegradation rate of benzene. The impact is limited, however, because sufficient oxygen disperses behind the ethanol plume into the slightly retarded benzene plume. A sensitivity analysis for two common spill scenarios showed that background oxygen concentrations and benzene retardation have the most significant influence on ethanol-induced benzene persistence. The results are highly relevant in light of the increasing use of ethanol-enhanced fuels throughout the world and the forthcoming ban of methyl tertiary-butyl-ether (MTBE) in California and its probable replacement by ethanol by the end of 2002.
  • Publication
    Métadonnées seulement
    A relative-least-squares technique to determine unique Monod kinetic parameters of BTEX compounds using batch experiments
    (1999)
    Schirmer, Mario 
    ;
    Butler, Barbara J
    ;
    Roy, James W
    ;
    Frind, Emil O
    ;
    Barker, James F
    An analysis of aerobic m-xylene biodegradation kinetics was performed on the results of laboratory batch microcosms. A modified version of the computer model BIO3D was used to determine the Monod kinetic parameters, k(max) (maximum utilization rate) and K-S (half-utilization constant), as well as the Haldane inhibition concentration, K-I, for pristine Borden aquifer material, The proposed method allows for substrate degradation under microbial growth conditions. The problem of non-uniqueness of the calculated parameters was overcome by using several different initial substrate concentrations. With a relative-least-squares technique, unique kinetic degradation parameters were obtained. Calculation of the microbial yield, Y, based on microbial counts from the beginning and the end of the experiments was crucial for reducing the number of unknowns in the system and therefore for the accurate determination of the kinetic degradation parameters, The kinetic parameters obtained in the present study were found to agree well with values reported in the literature. (C) 1999 Elsevier Science B.V. All rights reserved.