Anaerobic codigestion of the mechanically sorted organic fraction of a municipal solid waste with cattle manure in packed microcosms under batch conditions

Biodegradation of low-ethoxylated nonylphenols in a bioreactor packed with a new ceramic support (Vukopor ® S10)

This work was aimed at studying the possibility of biodegrading 4-nonylphenol and low ethoxylated nonylphenol mixtures, which are particularly recalcitrant to microbial degradation, by employing a biofilm reactor packed with a ceramic support (Vukopor® S10). A selected microbial consortium (Consortium A) was used to colonize the support. 4-Nonylphenol and ethoxylated nonylphenol degradation and mineralization capabilities were studied both in batch and continuous mode. The results showed that Vukopor® S10 was able to be colonized by an active biofilm for the degradation of the target pollutants with the reactor operating both in batch and continuous mode. On the other hand, pollutant adsorption on the support was negligible. FISH showed equal proportion of Alphaproteobacteria and Gammaproteobacteria in the Igepal CO-520 degrading reactor. A shift towards high proportion of Gammaproteobacteria was observed by supplying Igepal CO-210. PCR-density gradient gel electrophoresis (DGGE) analyses also evidenced that the biofilm evolved with time by changing the mixture applied and that Proteobacteria were the most represented phylum in the biofilm. Taken together, the data obtained provide a strong indication that the biofilm reactor packed with Vukopor® S10 and inoculated with Consortium A could potentially be used to develop a technology for the decontamination of 4-nonylphenol and low ethoxylated nonylphenol polluted effluents.

A continuous-flow approach for the development of an anaerobic consortium capable of an effective biomethanization of a mechanically sorted organic fraction of municipal solid waste as the sole substrate

An effective mesophilic continuous anaerobic digestion process fed only with a mechanically sorted organic fraction of municipal solid waste (MS-OFMSW) was developed. During a preliminary 3-month experimental phase, the microbial consortium was acclimated toward MS-OFMSW by initially filling the reactor with cattle manure and then continuously feeding it with MS-OFMSW. The Hydraulic Retention Time (HRT) and Organic Loading Rate (OLR) were 23 days and 2.5 g/L/day, respectively. After 4 weeks, the reactor reached stationary performances (84% COD removal yield, 0.15 L(CH₄)/g(COD removed) methane production yield). The acclimated consortium was then employed in a second run in which the reactor was operated under steady state conditions at the previous HRT and OLR for 73 days. The COD removal and the methane production yield increased up to 87% and 0.25 L(CH₄) /g(CODremoved), respectively. The capability of the acclimated consortium to biomethanize MS-OFMSW was further studied via batch digestion experiments, carried out by inoculating the target waste with reactor effluents collected at the beginning of first run and at the end of the first and second run. The best normalized methane production (0.39 L(CH₄) /g(initial COD)) was obtained with the inoculum collected at the end of the second run. Molecular analysis of the microbial community occurring in the reactor during the two sequential runs indicated that the progressive improvement of the process performances was closely related to the selection and enrichment of specific hydrolytic and acidogenic bacteria in the reactor.

Changes in bacterial communities from anaerobic digesters during petroleum hydrocarbon degradation

Anaerobic biodegradation of petroleum hydrocarbons (PHC) to methane has been recognized to occur in oil reservoirs and contaminated surface sites alike. This process could be employed efficiently for the treatment of contaminated materials, including petrochemical wastes and PHC-contaminated soil, since no external electron acceptor is required. Moreover, the controlled production of methane in digestion plants, similarly to the anaerobic digestion (AD) of energy crops or organic residues, would enable for energy recovery from these wastes. At present, little is known about the bacterial communities involved in and responsible for hydrocarbon fermentation, the initial step in PHC conversion to methane. In the present study, the fate of two different methanogenic communities derived from the AD of wastewater (WWT) and of biowaste, mixed with PHC-contaminated soil (SWT), was monitored during incubation with PHC using denaturing gradient gel electrophoresis (DGGE) of 16S rDNA genes amplified with Bacteria-specific primers. During 11 months of incubation, slight but significant degradation of PHC occurred in both sludges and distinct bacterial communities were developing. In both sludges, Bacteroidetes were found. In addition, in WWT, the bacterial community was found to be dominated by Synergistetes and Proteobacteria, while Firmicutes and unidentified members were abundant in SWT. These results indicate that bacterial communities from anaerobic digesters can adapt to and degrade petroleum hydrocarbons. The decontamination of PHC-containing waste via fermentative treatment appears possible.