Bioremediation: how to deal with removal efficiency uncertainty? An economic application.

Bioremediation is a remediation strategy, which has considerable strength but also certain limitations. Complex and uncertain relationships among biomass, contaminants, and nutrients lead to an uncertain level of removal efficiency. The uncertainty inherent to a bioremediation strategy should be addressed in the remediation selection process. In order to evaluate the bioremediation strategy economically, this study takes into account the reversibility of a decision. A decision tree structures the different remediation strategies, thus giving the possible courses of action open to the decision maker. The option value indicates the importance of having the possibility to reverse a previously made decision. Compared with conventional economic evaluation tools, more information to ground the selection made is revealed.

Groundwater remediation and the cost effectiveness of phytoremediation.

In 1999, phytoremediation was applied at the site of a Belgian car factory to contain two BTEX plumes. This case study evaluates the cost effectiveness of phytoremediation compared to other remediation options, applying a tailored approach for economic evaluation. Generally, when phytoremediation is addressed as being cost effective, the cost effectiveness is only determined on an average basis. This study however, demonstrates that an incremental analysis may provide a more nuanced conclusion. When the cost effectiveness is calculated on an average basis, in this particular case, the no containment strategy (natural attenuation) has the lowest cost per unit mass removed and hence, should be preferred. However, when the cost effectiveness is determined incrementally, no containment should only be preferred if the value of removing an extra gram of contaminant mass is lower than 320 euros. Otherwise, a permeable reactive barrier should be adopted. A similar analysis is provided for the effect determined on the basis of remediation time. Phytoremediation is preferred compared to 'no containment' if reaching the objective one year earlier is worth 7 000 euros.

Hydrogeological study for improved nature restoration in dune ecosystems--Kleyne Vlakte case study, Belgium.

In dune slacks a close coupling exists between changes in the hydrology and changes in species composition and vegetation structure. Consequently, there is a need to underpin nature restoration projects not only with ecologically relevant knowledge but also with scientifically sound hydrogeological data. In this paper, this necessity is illustrated through a study of the Flemish Nature Reserve 'The Zwindunes and Zwinpolders' (Belgian coastal plain) as an example. The management plan for the nature reserve suggests rewetting part of it to enhance its ecological value. The groundwater aspect was studied by means of field observations and mathematical modelling. First, fresh water head observation showed a mean groundwater flow from the nature reserve to the adjacent polder. Secondly, groundwater quality was studied with borehole measurements and water samples, resulting in a map of the fresh-salt water distribution and of water types. All available information was then put together in a density dependent groundwater flow model. The aim of this model was the description of current flow and fresh-salt water distribution and to simulate the impact of three possible rewetting scenarios. Rewetting will be accomplished by the infiltration of water in a depression, different lay-outs for which are considered. A zoomed in flow model based on a regional model was used to incorporate both local scale, which is of importance to ecology, and the larger scale, which determines general groundwater flow and fresh-salt water distribution. This modelling indicated differences between scenarios and was used to decide on the best rewetting strategy.

Identification and reliability of microbial aerobic respiration and denitrification kinetics using a single-well push-pull field test.

Methods to derive reaction rates of microbial processes are important since these processes are determining many chemical reactions influencing groundwater quality. Thereby, it is not only important to derive the parameters, but also to have a firm idea about the reliability with which these are determined. Analysis of residuals, sensitivity analyses and analysis of joint confidence intervals provide an interesting tool for this purpose. The method is illustrated in this paper using a push-pull test designed to derive aerobic respiration and denitrification. Therefore, a test solution containing dissolved oxygen and nitrate as reactive tracer and bromide as non-reactive tracer was injected in organic matter rich sediment. Afterwards, this test solution was extracted and water quality was monitored. ReacTrans, a finite-difference, axial-symmetric groundwater flow and solute transport model was developed to simulate the test and derive hydraulic, solute transport and chemical parameters. Aerobic respiration and denitrification were simulated with Michaelis-Menten kinetics. Maximum reaction rates (10.4 and 2.4 mmol/ld for aerobic respiration and denitrification respectively) and Michaelis constants (0.14 and 0.1 mmol/l for aerobic respiration and denitrification respectively) were determined. The reliability with which these parameters are derived is indicated by analysis of residuals, sensitivities and joint confidence intervals. This shows that the Michaelis-Menten parameters can be derived reliable with a push-pull test, whereas the test is insensitive to effective porosity and hydraulic conductivity. Because of the small scale of the test, longitudinal dispersivity was very small and therefore unidentifiable.

Monitoring reverse osmosis treated wastewater recharge into a coastal aquifer by environmental isotopes (B, Li, O, H).

Artificial recharge (AR) is gaining importance as a management tool in water stressed regions. The need to prove recovery performance requires new monitoring tools for AR systems. A novel combination of environmental isotope tracers (B, Li, O, H stable isotopes) was tested for the monitoring of AR of tertiary treated, desalinated domestic wastewater into a coastal dune aquifer in Flanders, Belgium. No significant isotope fractionation was observed for the treatment process, which includes low pH RO desalination. The wastewater, after infiltration through ponds and before recovery through pumping wells is characterized by low molar Cl/B ratios (3.3 to 5.2), compared to 130 to 1020 in the wider study area, delta(11)B values close to 0% per hundred, rather homogeneous delta(7)Li values (10.3 +/- 1.7% per hundred), and a 18O and 2H enrichment with respect to ambient groundwater due to evaporation in the infiltration ponds. This confers to the AR component a unique isotopic and geochemical fingerprint. Immediately downstream of the pumping wells and in the deeper part of the aquifer no evidence of AR wastewater could be found, indicating a high recovery efficiency. In the wider area and in the deeper part of the aquifer, isotopes evidence mixing of coastal rain and a fresh paleo-groundwater component with residual seawater as well as interaction with the aquifer material. Combining several isotope tracers provides independent constraints on groundwater flow and mixing proportions as a complement to hydrodynamic modeling and geochemical studies.

Brevibacillus levickii sp. nov. and Aneurinibacillus terranovensis sp. nov., two novel thermoacidophiles isolated from geothermal soils of northern Victoria Land, Antarctica.

Thirteen strains of endospore-forming bacteria were isolated from geothermal soils at Cryptogam Ridge, the north-west slope of Mt Melbourne, and at the vents and summit of Mt Rittmann in northern Victoria Land, Antarctica. 16S rRNA gene sequencing, SDS-PAGE and routine phenotypic characterization tests indicated that the seven isolates from the north-west slope of Mt Melbourne represent a novel species of Brevibacillus and that the six isolates from Cryptogam Ridge and the vents and summit of Mt Rittmann represent a novel species of Aneurinibacillus. Brevibacillus strains were not isolated from the sites at Mt Rittmann or Cryptogam Ridge and Aneurinibacillus strains were not isolated from the north-west slope of Mt Melbourne. Preliminary metabolic studies revealed that L-glutamic acid, although not essential for growth, was utilized by both species. The Brevibacillus species possessed an uptake system specific for L-glutamic acid, whereas the Aneurinibacillus species possessed a more general uptake system capable of transporting other related amino acids. Both species utilized a K(+) antiport system and similar energy systems for the uptake of l-glutamic acid. The rate of uptake by the Brevibacillus species type strain was 20-fold greater than that shown by the Aneurinibacillus species type strain. The names Brevibacillus levickii sp. nov. and Aneurinibacillus terranovensis sp. nov. are proposed for the novel taxa; the type strains are Logan B-1657(T) (= LMG 22481(T) = CIP 108307(T)) and Logan B-1599(T) (LMG 22483(T) = CIP 108308(T)), respectively.

Polyphasic identification of Bacillus and Brevibacillus strains from clinical, dairy and industrial specimens and proposal of Brevibacillus invocatus sp. nov..

Thirty-three clinical, dairy and industrial isolates of aerobic endospore-forming bacteria which were unreactive in routine identification tests were characterized genotypically by using amplified rDNA restriction analysis (ARDRA), 16S rDNA sequencing and DNA-DNA reassociation, and phenotypically by using fatty acid methyl ester (FAME) analysis, SDS-PAGE of whole-cell proteins, API Biotype 100 assimilation tests and 16 other routine phenotypic tests. Three isolates were identified as strains of Bacillus badius, 12 as Brevibacillus agri, including 3 strains associated with an outbreak of waterborne illness, 4 as Brevibacillus centrosporus and 2 as Brevibacillus parabrevis; 12 strains contaminating an antibiotic production plant were recognized as members of a new species, for which the name Brevibacillus invocatus is proposed, with the type strain LMG 18962T (= B2156T = CIP 106911T = NCIMB 13772T).

Occurrence of Bacillus sporothermodurans and other aerobic spore-forming species in feed concentrate for dairy cattle.

AIMS: To determine the aerobic spore composition and presence of Bacillus sporothermodurans spores in feed concentrate for dairy cattle. METHODS AND RESULTS: Six feed concentrate samples from five different farms were analysed. High levels of spores (up to 10(6) spores g(-1)) were found. Identification of 100 selected isolates was obtained by a combination of fatty acid methyl esters analysis, amplified ribosomal DNA restriction analysis and 16S rDNA sequencing. Ninety-seven isolates could be identified to the species level or assigned to a phylogenetic species group. Most of the isolates obtained after a heat treatment of 10 min at 80 degrees C were identified as members of the B. subtilis group (32 isolates), B. pumilus (25 isolates), B. clausii (eight isolates) and B. licheniformis (eight isolates). The isolates with very heat-resistant spores, obtained after a heat treatment of 30 min at 100 degrees C, were identified as members of the B. subtilis group (five isolates), B. sporothermodurans (three isolates), B. amyloliquefaciens (one isolate), B. oleronius (one isolate) and B. pallidus (one isolate). Bacillus cereus was present in each feed concentrate sample and was isolated using a selective mannitol egg yolk polymyxin agar medium. CONCLUSIONS: Feed concentrate for dairy cattle contains known as well as as yet unknown species of Bacillus and related genera with properties relevant to the dairy sector. SIGNIFICANCE AND IMPACT OF THE STUDY: The results formulate the hypothesis that feed concentrate can be a contamination source of spores, including those of B. sporothermodurans, for raw milk at the farm level.

Aerobic endospore-forming bacteria from geothermal environments in northern Victoria Land, Antarctica, and Candlemas Island, South Sandwich archipelago, with the proposal of Bacillus fumarioli sp. nov.

Aerobic endospore-forming bacteria were isolated from soils taken from active fumaroles on Mount Rittmann and Mount Melbourne in northern Victoria Land, Antarctica, and from active and inactive fumaroles on Candlemas Island, South Sandwich archipelago. The Mt Rittmann and Mt Melbourne soils yielded a dominant, moderately thermophilic and acidophilic, aerobic endospore-former growing at pH 5.5 and 50 degrees C, and further strains of the same organism were isolated from a cold, dead fumarole at Clinker Gulch, Candlemas Island. Amplified rDNA restriction analysis, SDS-PAGE and routine phenotypic tests show that the Candlemas Island isolates are not distinguishable from the Mt Rittmann strains, although the two sites are 5600 km apart, and 16S rDNA sequence comparisons and DNA relatedness data support the proposal of a new species, Bacillus fumarioli, the type strain of which is LMG 17489T.

Proposal of Virgibacillus proomii sp. nov. and emended description of Virgibacillus pantothenticus (Proom and Knight 1950) Heyndrickx et al. 1998.

A polyphasic study of strains originally received as Bacillus (now Virgibacillus) pantothenticus, along with strains representing species belonging to Bacillus, Halobacillus and Paenibacillus, was undertaken using amplified rDNA restriction analysis (ARDRA), fatty acid methyl ester (FAME) analysis, SDS-PAGE of whole-cell proteins and routine diagnostic characters comprising 61 biochemical tests in the API system and 15 observations of vegetative cell and sporangial morphology. It revealed the presence within Virgibacillus of an as yet undescribed new species, for which the name Virgibacillus proomii is proposed; V. proomii can be distinguished from V. pantothenticus and members of Bacillus sensu stricto, and from members of Paenibacillus and other aerobic endospore-forming bacteria, by routine phenotypic tests. The type strain of Virgibacillus proomii is LMG 12370T.