Performances and microbial features of a granular activated carbon packed-bed biofilm reactor capable of an efficient anaerobic digestion of olive mill wastewaters

Abstract

Anaerobic digestion of olive mill wastewaters is generally performed in anaerobic contact bioreactors where the removal of toxic phenols is often unsatisfactory. In the present work we show that a granular activated carbon packed-bed biofilm reactor can be successfully used to achieve effective and reproducible wastewater decontamination even at high organic loads. A comparison of 16S rRNA gene sequences of the inoculum and of biomass samples from different districts of the reactor revealed enrichment of specific microbial populations, probably minor members of the inoculum and/or of the olive mill wastewaters. They mainly consisted of the members of Proteobacteria, Flexibacter-Cytophaga-Bacteroides, and sulphate-reducing bacteria. The dominant sequence among Archaea (70% of clones) was closely related to Methanobacterium formicicum.

Response of methanogen populations to organic load increase during anaerobic digestion of olive mill wastewater

“…The process performances were comparable to those described by other authors. 5 In contrast to a recent study of a GAC biofilm reactor treating OMW, 5 where the only methanogen found was Methanobacterium formicicum, here Methanobacteriaceae and Methanosaeta/Methanothrix were the main methanogens in the reactor. These groups changed in relative abundance in response to increasing VOL.…”

“…3,4 However, process efficiency can be seriously reduced owing to the presence of high concentrations (8-16 g L −1 ) of phenolic compounds. 5 During the degradation of complex organic matter by anaerobic digestion, methanogenic Archaea are the final catalysers of the food chain. By removing the metabolic products of syntrophic acetogens, methanogens play a regulative role in maintaining the overall efficiency of the process.…”

“…8,9 To our knowledge, only one study has described the behaviour of methanogenic Archaea in the biofilm of an anaerobic reactor treating OMWs. 5 That study was performed in a granular activated carbon (GAC) packed bed biofilm reactor and showed that the main methanogenic Archaea in the biofilm were related to hydrogenotrophic Methanobacterium formicicum.…”

The Microbiology of Olive Mill Wastes

“…Actinomyces suimastitidis and Staphylococcus felis were minor constituents of the biofilm formed [81]. Investigation of microbial dynamics in a granular activated carbon packed-bed anaerobic bioreactor fed with OMW resulted in the identification of members of Gammaproteobacteria , Deltaproteobacteria , and Bacteroidetes as well as fermentative bacteria of the genera Clostridium ( Firmicutes ) and Anaerobaculum ( Synergistetes ) [82]. Syntrophus spp., which were in syntrophic relationship with methanogenic Archaea , were detected, while sulphate-reducing bacteria were identified as the result of the high sulphate concentration in the OMW digested.…”

Characteristics of Chars from Woody Wastes and Their Application to Immobilization Carriers for Fermentative Hydrogen Production

“…Therefore, the present study has additional significance in terms of expanding the usability of char materials. There have been previous studies in which activated carbon was used as the immobilization carrier in methane fermentation (Bertin et al, 2004), and, with respect to hydrogen production, activated carbon has been used as a core for granulation . However, few examples exist where woody waste chars are used in fermentative hydrogen production.…”