Disintegration of municipal waste-activated sludge (WAS) is regarded as a prerequisite of the anaerobic digestion process to reduce sludge volume and improve biogas yield. Pretreatment of WAS using thermo-alkaline (TA), H2O2 oxidation, electrolysis and electro-oxidation (EO) processes were investigated and compared in term of COD solubilization and biogas production. For each pretreatment, the influences of different operational variables were studied in detail. At optimum conditions, EO gave the maximum COD solubilization (28 %). The effects of pretreatments under the optimum conditions on anaerobic digestion were experienced with biochemical methane potential assay. Significant increases in biogas yield up to 78 and 40 % were observed respectively in the EO and TA pretreated samples compared to raw sludge. Results clearly revealed that the application of EO is a significant alternative method for the improvement of WAS anaerobic digestion.

No abstract

There are increasing concerns over the harmful effects of the phosphate industry on human health and quality of life worldwide, including the Tunisian Chemical Group (GCT) in Sfax, which generates various malodorous gas fractions, such as hydrogen sulfide (H 2 S) and fetid mercaptans, causing nuisance to employees and local residents. Accordingly, the present study aimed to investigate the ability of an adapted microbial consortium isolated from the gas-washing wastewaters (GWWs) generated from GCT to degrade hazardous and malodorous mercaptans. A novel mesophilic bacterial strain (SH6), which was noted to display particularly high mercaptan degradation potential, was isolated from the adapted consortium growing on those GWWs and several malodorous mercaptans after enrichment on 1-dodecanethiol. The results from 16 rRNA gene sequencing and identity analysis revealed that the SH6 isolate belonged to Staphylococcus genus, with a high sequence similarity to Staphylococcus capitis (99.7 %). The SH6 strain was able to completely degrade 1-dodecanethiol, used as the sole carbon and energy source, after 72 h of incubation at 37°C and 180 rpm. A decrease in the surface tension of cell-free culture supernatants was observed during the oxidation of dodecanethiol, suggesting the production of surface-active compounds. The stain was also able to grow on other mercaptans, such as 1,8-octanedithiol and 2,3-butanedithiol, which further supports its potential candidacy for application in the bioremediation of mercaptan-contaminated sites. Overall, the findings of the present study indicate that the SH6 strain might offer promising opportunities for the development of more adapted, efficient and cost-effective bio-disodoration strategies.

No abstract