1,721,060 research outputs found
Comment on “Microbiology and biochemistry of the enhanced biological phosphate removal process” by Mino et al.
No full text
An aerobic fixed-phase biofilm reactor system for the degradation of the low-molecular weight aromatic compounds occurring in the effluents of anaerobic digestors treating olive mill wastewaters
No full textAn aerobic co-culture, prepared by combining Ralstonia sp. LD35 and Pseudomonas putida DSM1868, was recently found to be capable of extensively degrading many of the hydroxylated and/or methoxylated benzoic, phenylacetic and 3-phenyl-2-propenoic acids occurring in the olive mill wastewaters (OMWs). In the perspective of developing a biotechnological process for the degradation of low-molecular weight (MW) aromatic compounds occurring in the effluents of anaerobic digestors treating OMWs, the capability of this bacterial co-culture of biodegrading a synthetic mix of the above mentioned compounds and the aromatic compounds of an anaerobic OMW-treatment plant effluent in the physiological state of immobilised cells was investigated. Two aerobic fixed-bed biofilm reactors were developed by immobilising the co-culture cells on Manville silica beads and on polyurethane foam cubes. Both supports were found to give rise to a microbiologically stable and biologically active biofilm. The two biofilm reactors were found to be similarly capable of rapidly and completely biodegrading the components of a synthetic mix of nine monocyclic aromatic acids typically present in OMWs and the low-MW aromatic compounds occurring in the anaerobic effluent in batch conditions. However, in the same conditions, the silica bead-packed reactor was found to be more effective in the removal of high-MW phenolic compounds from the anaerobic effluent with respect to the polyurethane cube-packed reactor. These results are encouraging in the perspective of using the co-culture as immobilized cells for developing a continuous biotechnological process for the post-treatment of effluents with low-MW aromatic compounds produced by anaerobic digestors treating OMWs. © 2001 Elsevier Science B.V
A granular activated carbon (GAC) packed-bed reactor for a more efficient anaerobic treatment and valorization (via methane production) of olive mill wastewaters
No full textFeed frequency in a Sequencing Batch Reactor strongly affects the production of polyhydroxyalkanoates (PHAs) from volatile fatty acids
No full textThe production of polyhydroxyalkanoates (PHAs) by activated sludge selected in a sequencing batch reactor (SBR) has been investigated. Several SBR runs were performed at the same applied organic load rate (OLR), hydraulic retention time (HRT) and feed concentration (8.5 g COD L-1 of volatile fatty acids, VFAs) under aerobic conditions. The effect of the feeding time was only evaluated with a cycle length of 8 h; for this particular cycle length, an increase in the storage response was observed by increasing the rate at which the substrate was fed into the reactor (at a fixed feeding frequency). Furthermore, a significantly stronger effect was observed by decreasing the cycle length from 8 h to 6 h and then to 2 h, changing the feed frequency or changing the organic load given per cycle (all of the other conditions remained the same): the length of the feast phase decreased from 26 to 20.0 and then to 19.7% of the overall cycle length, respectively, due to an increase in the substrate removal rate. This removal rate was high and similar for the runs with cycle lengths of 2 h and 6 h in the SBR. This result was due to an increase in the selective pressure and the specific storage properties of the selected biomass. The highest polymer productivity after long-term accumulation batch tests was 1.7 g PHA L-1 d(-1), with PHA content in the biomass of approximately 50% on a COD basis under nitrogen limitation. The DGGE profiles showed that the good storage performance correlated to the development of Lampropedia hyalina, which was only observed in the SBR runs characterized by a shorter cycle length
Acetogenic inoculum selection for acetate production from waste biomasses via thermal shock treatment
Full text linkInnovative treatment and utilization of waste biomass streams are crucial for increase environmental sustainability of human activities. Sewage sludge from the biological degradation of biomass can be valorized for the selection of biocatalysts capable to convert CO2 into valuable products. Indeed, chemoautotrophic microorganisms, like methanogens and acetogens, respectively, are able to convert CO2 into CH4 or acetate by using hydrogen as electron donor, i.e., their utilization for several bio-based CO2 reutilization processes has been widely proposed by several authors. Chemoautothrophic acetogens are widely present in waste streams deriving from the organic matter degradation, however, due to the syntrophic relationship between acetogens and acetoclastic methanogens in anaerobic environments, autothropihc acetate results immediately converted into methane. Therefore, the selection of an acetogenic inoculum which allow to obtain CO2 reduction into acetate, requires methanogens inhibition. Among the different methanogen’s inhibition strategies, the most common method is the use of BES (bromo-ethane sulphonate) which results a not scalable technique for large scale application. A most promising and sustainable approach is offered by the adoption of a thermal treatment which allows to the selection of an acetogenic inoculum, thanks ot the sporogenous capacity of acetogenic bacteria. This work presents the results obtained in the thermal pre-treatment of different type of waste biomasses coming from pilot and full-scale biological processes for the selection of an acetogenic inoculum able to convert CO2 into acetate. Each waste biomass was treated by a thermal shock procedure that consisted in the treatment of the dried biomass at 120°C for 2 hours. Acetogenic inoculums obtained by the thermal pre-treatment of an acidogenic fermentate, an activated sludge and a mesophilic anaerobic digestate, were tested under hydrogenophilic conditions in comparison with blank tests and raw inoculums. The results clearly indicate the effectiveness of the thermal pre-treatment in the selection of the acetogenic microorg
Nuovi processi bio-elettrochimici basati sul trasferimento extracellulare di elettroni: applicazioni in acmpo ambientale ed industriale
No full textBioelectrochemical production of methane by a hydrogenophilic methanogenic culture
No full textIn this research, we investigated the bioelectrochemical production of methane gas from carbon dioxide reduction by using a microbial biocathode, based on a hydrogenophilic methanogenic culture, not previously acclimated in bioelectrochemical systems. Methane production was found to proceed on plain carbon cathodes, polarized at potentials more negative than -650 mV (vs. SHE), both via direct extracellular electron transfer and via abiotically produced hydrogen gas (i.e., via hydrogenophilic methanogenesis). The relative contribution of these routes to methane production was highly dependent on the cathode potential. The use of redox mediators (i.e.: Neutral Red, E°'= -325 mV vs. SHE) allowed to carry out the reaction at less reducing potentials (-450 mV vs. SHE), even thought methane production rates were remarkable lower than in the mediator-less systems. However, methane production could be increased through the formation of a biofilm on high specific surface electrodes
Evaluation of carbon storage by aerobic batch tests on real wastewater and activated sludge
No full textIntegrated treatment of olive oil mill effluents (OME): study of ozonation coupled with anaerobic digestion
No full text- …
