Elsevier

Chemosphere

Volume 63, Issue 4, April 2006, Pages 600-608
Chemosphere

Biostimulation and bioaugmentation enhances aerobic biodegradation of dichloroethenes

https://doi.org/10.1016/j.chemosphere.2005.08.027Get rights and content

Abstract

The accumulation of dichloroethenes (DCEs) as dominant products of microbial reductive dechlorination activity in soil and water represent a significant obstacle to the application of bioremediation as a remedial option for chloroethenes in many contaminated systems. In this study, the effects of biostimulation and/or bioaugmentation on the biodegradation of cis- and trans-DCE in soil and water samples collected from contaminated sites in South Africa were evaluated in order to determine the possible bioremediation option for these compounds in the contaminated sites. Results from this study indicate that cis- and trans-DCE were readily degraded to varying degrees by natural microbial populations in all the soil and water samples tested, with up to 44% of cis-DCE and 41% of trans-DCE degraded in the untreated soil and water samples in two weeks. The degradation rate constants ranged significantly (P < 0.05) between 0.0938 and 0.560 wk−1 and 0.182 and 0.401 wk−1, for cis- and trans-DCE, respectively, for the various treatments employed. A combination of biostimulation and bioaugmentation significantly increased the biodegradation of both compounds within two weeks; 14% for cis-DCE and 18% for trans-DCE degradation, above those observed in untreated soil and water samples. These findings support the use of a combination of biostimulation and bioaugmentation for the efficient biodegradation of these compounds in contaminated soil and water. In addition, the results clearly demonstrate that while naturally occurring microorganisms are capable of aerobic biodegradation of cis- and trans-DCE, biotransformation may be affected by several factors, including isomer structure, soil type, and the amount of nutrients available in the water and soil.

Introduction

The frequently observed accumulation of the isomers of dichloroethenes (DCEs) as the dominant products of microbial reductive dechlorination activity in soil and water under anaerobic conditions and the lack of understanding of the factors controlling biodegradation of DCEs in situ represent significant obstacles to the application of bioremediation as a remedial option in many contaminated systems (Pavlostathis and Zhuang, 1993, Gibson et al., 1994, Bradley and Chapelle, 1997). Therefore, pump-and–treat systems using air stripping and adsorption onto granular activated carbon are the primary technologies used for removing volatile organic compounds (VOC), including DCEs. A decade of performance data, however, has demonstrated that these systems are not as efficient as once thought (Haley et al., 1991). In situ bioremediation has therefore been proposed as an alternative method in order to reduce time and cost for site restoration of systems contaminated with this group of compounds (Skeen et al., 1993, Saaty et al., 1995).

Along with deciding whether or not a site should be remediated using on site treatment or in situ treatment, it is necessary to decide the bioremediation options that needed to be employed. Three types of bioremediation are predominant in the industry today: natural attenuation, biostimulation, and bioaugmentation. The simplest method of bioremediation to implement is natural attenuation, where contaminated sites are only monitored for contaminant concentration to assure regulators that natural processes of contaminant degradation are active (Kaplan and Kitts, 2004). Biostimulation requires adjustments to the site (contaminated soil or water) in order to provide bacterial communities with a favourable environment in which they can effectively degrade contaminants. This includes the addition of nitrogen, phosphorus, and trace minerals while also making appropriate pH adjustments for the proliferation of indigenous microorganisms, hence speeding up the bioremediation process (Venosa et al., 1996, Salanitro et al., 1997). In cases where natural communities of degrading bacteria are present in low numbers or even absent, bioaugmentation, i.e., the addition of contaminant-degrading organisms, can speed up the degradation process (Al-Awadhi et al., 1996, Van Limbergen et al., 1998).

Partial dehalogenation of chloroethenes under anaerobic conditions has led to the speculation that a subsequent aerobic treatment may be necessary. Efforts have therefore been tailored towards investigating the biodegradation of DCEs under aerobic conditions (Malachowsky et al., 1994, Hopkins and McCarty, 1995). Several recent investigations indicate that microorganisms can oxidize DCEs to CO2 in the absence of apparent alternative substrates in microcosms (Bradley et al., 1998, Bradley and Chapelle, 1998a, Bradley and Chapelle, 1998b, Klier et al., 1999). Significant aerobic oxidation of DCE was demonstrated for an organic-rich stream bed sediment (Bradley and Chapelle, 1998a, Bradley and Chapelle, 1998b), organic-rich surface soils (Klier et al., 1999), and organic-poor aquifer sediments (Bradley et al., 1998, Bradley and Chapelle, 1998a, Klier et al., 1999). However, to the best of our knowledge, no study has been conducted to investigate the potential for aerobic biodegradation of DCEs in microcosms incorporating soil and water from contaminated sites in Africa, with the view of providing baseline information for the possible natural attenuation of these compounds in contaminated sites in the African continent.

In this paper, we report the aerobic biodegradation of cis- and trans-DCE by indigenous microorganisms in soil and water collected from some contaminated sites in South Africa as well as the effects of biostimulation and/or bioaugmentation on the biodegradation of the compounds in soil and water microcosm settings under aerobic conditions pursuant to providing necessary information for the possible in situ bioremediation of these compounds in contaminated sites in South Africa.

Section snippets

Sample collection

The soil samples used in this study were collected from separate locations to represent different soil types (clay and loam soil), while the wastewater samples were collected from the clarification tanks of the Northern and New Germany wastewater treatment plants in Durban, KwaZulu-Natal, South Africa. The soil samples were sieved using a 1.7 mm laboratory test sieve and transported immediately to the laboratory after collection and stored at 4 °C prior to the construction of the microcosms.

Bacterial cultures

The

Soil and wastewater characterization

The physicochemical properties of the soil and wastewater samples used for the microcosm experiments are listed in Table 1, Table 2, respectively. The soil sample AE was characterized as sandy clay soil, while soil sample BF was classified as a sandy soil based on textural analysis (Table 1). The pH of the soil and the water samples ranged between 4.92–5.02 and 6.94–6.98, respectively. Sodium concentration was found to be 10-fold higher, potassium threefold higher, calcium about one hundred and

Discussion

Some chlorinated compounds act as sole carbon source for some microorganisms under aerobic conditions and several microorganisms have been isolated that can use a number of chlorinated compounds as growth substrates (Stucki et al., 1983, Janssen et al., 1985). However, there is very little information on the potential for aerobic biodegradation with dichloroethenes as a sole carbon source, despite the observed accumulation of these compounds as products of reductive dechlorination of higher

Acknowledgements

This study was supported by the National Research Foundation (NRF) of South Africa, Water Research Commission of South Africa and the South African Consortium for Development and Environment—Industry and Urban Areas (SACUDE—I & UA), Denmark. The authors wish to express their appreciation to Dr. D.H. Pienaar of the Department of Chemistry, University of KwaZulu-Natal (Westville Campus) for assistance with gas chromatography. The first author is grateful to the management of Obafemi Awolowo

References (39)

  • D.K. Button et al.

    Interactions between marine bacteria and dissolved-phase and beached hydrocarbons after the Exxon Valdez oil spill

    Appl. Environ. Microbiol.

    (1992)
  • N.V. Coleman et al.

    Biodegradation of cis-dichloroethene as the sole carbon source by a β-proteobacterium

    Appl. Environ. Microbiol.

    (2002)
  • T.W. Federle et al.

    Spatial distribution of microbial biomass, activity, community structure, and the biodegradation of linear alkylbenzene sulfonate (LAS) and linear alcohol ethoxylate (LAE) in the subsurface

    Microb. Ecol.

    (1990)
  • G.W. Gee et al.

    Particle size analysis by hydrometer: a simplified method for routine textural analysis and a sensitivity test of measured parameters

    Soil Sci. Soc. Am. J.

    (1979)
  • T.J. Gentry et al.

    Soil microbial population dynamics following bioaugmentation with a 3-chlorobenzoate-degrading bacterial culture: bioaugmentation effects on soil microorganisms

    Biodegradation

    (2001)
  • P. Gerhardt et al.

    Manual of methods for general bacteriology

    (1991)
  • S.A. Gibson et al.

    Effects of three concentrations of mixed fatty acids on dechlorination of tetrachloroethene in aquifer microcosms

    Environ. Toxicol. Chem.

    (1994)
  • M.G. Goldstein et al.

    Reasons for possible failure of inoculation to enhance biodegradation

    Appl. Environ. Microbiol.

    (1985)
  • J.L. Haley et al.

    Evaluating the effectiveness of groundwater extraction systems

    Groundwater Monit. Rev.

    (1991)
  • Cited by (0)

    View full text