1,721,054 research outputs found
Dynamics of Phosphorus and Organic Substrates in Anaerobic and Aerobic Phases of a Sequencing Batch Reactor
No full textThis paper describes a lab-scale experimentation carried out to study enhanced biological phosphate removal (EBPR) in a sequencing batch reactor (SBR). The synthetic feed used was based on peptone and glucose as organic substrate to simulate the readily biodegradable fraction of a municipal wastewater (Wentzel et al., 1991). The experimental work was divided into two runs, each characterized by different operating conditions. The phosphorus removal efficiency was considerably higher in the absence of competition for organic substrate between P-accumulating and denitrifying bacteria. The activated sludge consisted mainly of peculiar microorganisms recently described by Cech and Hartman (1990) and called “G bacteria”. The results obtained seem to be inconsistent with the general assumption that the G bacteria are characterized by anaerobic substrate uptake not connected with any polyphosphate metabolism. Supplementary anaerobic batch tests utilizing glucose, peptone and acetate as organic substrates show that the role of acetate in the biochemical mechanisms promoting EBPR may not be so essential as it has been assumed till now.</jats:p
Design and realization of a field test for the feasibility evaluation of chlorinated solvent contaminated aquifer remediation by enhanced natural attenuation (ENA)
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The effect of micropollutants (organic xenobiotics and heavy metals) in the activated sludge process
No full textIn situ molecular tracking of dehalogenating bacteria: from microbial enrichments to field sample
No full textRemediation of contaminated sites in Italy: state of the art of technologies and plannig & design criteria
No full textRemediation of contaminated sites in Italy has been so far governed by the so-called Ronchi Decree (Ministerial Decree 2/97) and by the subsequent Ministerial Decree 471/99, which laid down detailed procedural and technical provisions. Most of the site remediation projects conducted in Italy have fallen under the scope of the above Decrees.
This legislation was recently revised by Legislative Decree no. 152 of 3 Apr. 2006 (hereafter called "Decree 152/2006"), consolidating and superseding all previous laws and regulations on environmental matters (including general legislation on water protection, namely Legislative Decree no. 152 of 11 MayI999). On the other hand, Decree 152/2006, including provisions on remediation of contaminated sites, is already being overhauled. Against this background, it is useful to make a critical analysis of the seven years of application of the prior legislation (Ministerial Decree 471/99), in order to derive suggestions for the more technical aspects of the ongoing revision.
The following analysis considers both remediation and emergency containrnent of contaminated groundwater and soil, focusing on the interaction between the legislative-regulatory framework and the consequent technological choices and, namely, on their planning & design. The analysis is of a merely qualitative nature and hinges on the direct experience of the Authors, acting as remediation specialists and technical and scientific consultants. Therefore, the analysis solely reflects their personal opinions.
Table 1 gives a qualitative overview of the technologies used in Italy for rehabilitating contarninated sites. The Table shows that most of the technological options available in the state of the art have been used.
Largely dominant among them were ex-situ technologies, especially excavation and disposal for soil and Pump & Treat (P&T) for water. These approaches, whose use was at tirnes inevitable, were not particularly effective in terms of environrnental sustainability. Indeed, in both cases, the contarninated resource is not restored to its original or potential uses. Even if encouraging progress has recently been made, the use of in-situ technologies has remained marginal and should thus be intensified. Among the latter technologies, mention is to be made of those largely used in other countries, such as permeable reactive barriers, aerobic and anaerobic bioremediation and in-situ chernical oxidation
Olive mill wastewaters anaerobid digestion in mesophilic and thermophilic batch packed-bed biofilm reactors for the accumulation of volatile fatty acids as monomers employed in the biological production of polyhydroxyalkanoates
No full textPolyhydroxyalkanoates (PHAs) are bioplastic whose properties and applicability are quite similar to these of polypropylene. In order to make PHA industrial production feasible, new low-cost processes have to be developed. In this research, an innovative process for PHA production is being studied. This process consists of three stages. In the first stage (anaerobic conditions), the acidogenic fermentation transforms an organic substrate into a mixture of volatile fatty acids (VFAs), the most suitable substrate for PHA production. In the second stage (aerobic conditions), the effluent of the first stage is fed to a Sequencing Batch Reactor (SBR), where the periodic feeding (“feast and famine” conditions) enriches the mixed microbial culture of the PHA-producing microorganisms. In order to optimize PHA productivity, this stage is operated at the highest organic load allowed from the need of maintain strong selective pressure on the sludge. In the third (batch) stage (aerobic conditions), the excess sludge from the second stage is fed with the effluent of acidogenic fermentation in order to increase its PHA content up to the maximum value. Then this PHA-rich sludge flows to the downstream processing of PHA.
Regarding the choice of the organic substrate to be used as feedstock for the process, olive mill wastewaters (OMWs) are particularly interesting. OMWs are the liquid effluent resulting from olive oil producing processes. Due to their high COD load, they are generally considered effluents of high environmental concern. The possibility of developing a biotechnological process fed with OMWs and addressed to the production of VFAs was explored in the present research. To this aim, Four packed-bed biofilm reactors (PBBRs) were employed in batch conditions in the anaerobic acidogenic digestion of an OMW. The effect on the process of the packing material and of the temperature were studied by filling two of the PBBRs with granular activated carbon (GAC) and the other two with ceramic cubes (VS), and by thermostating one GAC- and one VS-PBBR at 35°C and the other two at 55°C. The reactors were inoculated with an acclimated OMW-degrading consortium employed in a previous research (Bertin et al. 2004). Two one-month batch experiments were carried out by feeding the reactors with a diluted and amended OMW. For both experiments, the higher VFA production was observed in the PBBR filled with SV and operating at 35°C, where more then 3 g/l of VFA accumulated, this corresponding to a conversion of about the 60% of the initial COD. Acetic acid was the main component of the VFA mixtures collected from all the PBBRs. Significant concentrations of both propionic and butirric acid were also observed.
Bertin L.; Colao M.C.; Ruzzi M.; Fava F. "Technological features and molecular microbial characterisation of a granular activated carbon packed-bed biofilm reactor capable of an effective anaerobic digestion of olive mill wastewaters." FEMS MICROBIOLOGY ECOLOGY, 48:413-423 (2004
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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