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- Title
Molecular Monitoring of SRB Community Structure and Dynamics in Batch Experiments to Examine the Applicability of in situ Precipitation of Heavy Metals for Groundwater Remediation.
- Authors
Geets, Joke; Borremans, Brigitte; Vangronsveld, Jaco; Diels, Ludo; Van Der Lelie, Daniel
- Abstract
Background, Aims and Scope. Sulfate-reducing bacteria (SRB) are known for their capacity to reduce and precipitate heavy metals (HM) as metal sulfides, offering the opportunity to create an in situ reactive zone for the treatment of heavy metal-contaminated groundwater, a process called in situ metal precipitation (ISMP). The applicability of the ISMP technology first has to be investigated at a laboratory scale before going into an on site application. The evaluation and optimization of the ISMP process is facilitated when physical/chemical analysis techniques are combined with molecular tools that specifically monitor the abundance, diversity and dynamics of the indigenous sulfate reducing microbial community. In this study, batch experiments were conducted in order to investigate the feasibility of ISMP as a groundwater remediation strategy for an industrial site contaminated with elevated levels of Zn, Cd, Co and Ni. Methods. The potential of different types of carbon source/ electron donor (lactate, acetate, methanol, ethanol, Hydrogen Release Compound®, molasses) to stimulate the sulfate reduction and metal precipitation activity of the naturally present (or indigenous) SRB community was explored. In addition, the effect of amending vitamin B12 and yeast extract was evaluated. The ISMP process was monitored by combining analytical analyzes of process parameters (SO42-concentration, heavy metal concentrations, pH, Eh) with molecular tools such as SRB subgroup and genus specific PCR, denaturing gradient gel electrophoresis (DGGE), and phylogenetic analysis of clone sequences, based on either the 16S rRNA or the dsr (dissimilatory sulfite reductase) gene. Results and Discussion. The efficiency of different carbon-sources to stimulate the ISMP process followed the order HRC® > molasses > methanol > lactate > ethanol > acetate. Within 10 weeks, the highest sulfate and metal removal efficiencies ranged from 85% to 99%. Addition of yeast extract boosted the ISMP process, whereas vitamin B12 negligibly affected SRB activity. Analysis of the sulfate reducing population by SRB subgroup and genus specific PCR demonstrated that members of the genus Desulfosporosinus dominated in all batch tests, while 16S rDNA DGGE profiles additionally revealed the presence in the microbial communities of non-sulfate reducing bacteria within the family Clostridiam and the ϵ-proteobacteria. The dsrB-based DGGE profiles allowed us to assess the diversity and dynamics of the sulfate reducing community and added to a better understanding of the effects of different batch conditions on the ISMP process. Remarkably, all dsrB sequences affiliated with the dsrB gene sequence cluster found in Desulfotomaculum, which received their xenologous dsrB gene from the δ-proteobacteria. Conclusions. The batch experiments, which aimed at stimulating the activities of the indigenous SRB communities, demonstrated that these communities were present and that their activities could be used to obtain efficient in situ precipitation of the contaminating heavy metals. This opens the possibility to test this concept in the future as an on site demonstration as part of the groundwater strategy for the heavy metal contaminated site.…
- Subjects
ENVIRONMENTAL protection; POLLUTION prevention; ANALYTICAL chemistry; PRECIPITATION (Chemistry); HEAVY metals removal (Sewage purification); METAL sulfides; IN situ bioremediation; INDUSTRIAL contamination; WATER pollution
- Publication
Journal of Soils & Sediments: Protection, Risk Assessment, & Remediation, 2005, Vol 5, Issue 3, p149
- ISSN
1439-0108
- Publication type
Article
- DOI
10.1065/jss2004.12.125