Bio-methane production variation under different draw solute reverse diffusions in an anaerobic digester simulated for FO-AnMBR

This study was conducted to investigate the relationship among the reverse diffusion of fertilizer draw solute, bacteria community and bio-methane production rate in the FDFO-AnMBR system. Three fertilizers were evaluated in this study, namely KCl, KNO3 and KH2PO4. Results showed that bio-methane production decreased with the increase in reverse fertilizer diffusion. The pyrosequencing results revealed that bacteria communities of different fertilizers were clearly different from each other. The bacteria community of sludge with KH2PO4 added was very similar to the blank control. The sludge with KCl exhibited a higher similarity to the sludge with KH2PO4 than KNO3. Moreover, the nitrogen gas production species (Proteobacteria: Comamonas) was found to have a higher abundance (1.2) in sludge with KNO3 than the sludge with other fertilizers (0). This study demonstrated that the fertilizer reverse diffusion has a negative effect on the bio-methane production, probably by influencing the sludge bacteria community via environment modification.