Enhanced anaerobic digestion of dairy wastewater in a granular activated carbon amended sequential batch reactor

This study investigated the potential of granular activated carbon (GAC) supplementation to enhance anaerobic degradation of dairy wastewater. Two sequential batch reactors (SBRs; 0.8 L working volume), one control and another amended with GAC, were operated at 37 degrees C and 1.5-1.6 m/h upflow velocity for a total of 120 days (four cycles of 30 days each). The methane production at the end of each cycle run increased by about 68%, 503%, 110%, and 125% in the GAC-amended SBR, compared with the Control SBR. Lipid degradation was faster in the presence of GAC. Conversely, the organic compounds, especially lipids, accumulated in the absence of the conductive material. In addition, a reduction in lag phase duration by 46%-100% was observed at all four cycles in the GAC-amended SBR. The peak methane yield rate was at least 2 folds higher with GAC addition in all cycles. RNA-based bacterial analysis revealed enrichment of Synergistes (0.8% to 29.2%) and Geobacter (0.4% to 11.3%) in the GAC-amended SBR. Methanolinea (85.8%) was the dominant archaea in the biofilm grown on GAC, followed by Methanosaeta (11.3%), at RNA level. Overall, this study revealed that GAC supplementation in anaerobic digesters treating dairy wastewater can promote stable and efficient methane production, accelerate lipid degradation and might promote the activity of electroactive microorganisms.

Automated summary

This study investigated the potential of granular activated carbon (GAC) supplementation in enhancing anaerobic degradation of dairy wastewater. The results showed that the addition of GAC significantly increased methane production and accelerated lipid degradation, while the absence of GAC led to the accumulation of organic compounds. Furthermore, GAC supplementation reduced the lag phase duration and increased methane yield rate. Bacterial analysis revealed the enrichment of Synergistes and Geobacter in the GAC-amended reactor, with Methanolinea being the dominant archaea in the biofilm grown on GAC. Overall, this study demonstrated that GAC supplementation can promote stable and efficient methane production, accelerate lipid degradation, and potentially enhance the activity of electroactive microorganisms in anaerobic digesters treating dairy wastewater.