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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
    Laboratory evidence of MTBE biodegradation in Borden aquifer material
    (2003)
    Schirmer, Mario 
    ;
    Butler, Barbara J
    ;
    Church, Clinton D
    ;
    Barker, James F
    ;
    Nadarajah, Nalina
    Mainly due to intrinsic biodegradation, monitored natural attenuation can be an effective and inexpensive remediation strategy at petroleum release sites. However, gasoline additives such as methyl tert-butyl ether (MTBE) can jeopardize this strategy because these compounds often degrade, if at all, at a slower rate than the collectively benzene, toluene, ethylbenzene and the xylene (BTEX) compounds. Investigation of whether a compound degrades under certain conditions, and at what rate, is therefore important to the assessment of the intrinsic remediation potential of aquifers. A natural gradient experiment with dissolved MTBE-containing gasoline in the shallow, aerobic sand aquifer at Canadian Forces Base (CFB) Borden (Ontario, Canada) from 1988 to 1996 suggested that biodegradation was the main cause of attenuation for MTBE within the aquifer. This laboratory study demonstrates biologically catalyzed MTBE degradation in Borden aquifer-like environments, and so supports the idea that attenuation due to biodegradation may have occurred in the natural gradient experiment. In an experiment with batch microcosms of aquifer material, three of the microcosms ultimately degraded MTBE to below detection, although this required more than 189 days (or >300 days in one case). Failure to detect the daughter product tert-butyl alcohol (TBA) in the field and the batch experiments could be because TBA was more readily degradable than MTBE under Borden conditions. (C) 2002 Elsevier Science B.V. All rights reserved.
  • 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.