Simultaneous methane production and wastewater reuse by a membrane-based process: Evaluation with raw domestic wastewater

In this study, a membrane-based process was applied to simultaneously reclaim methane and generate reused water from raw domestic wastewater. The system was comprised of up-flow anaerobic sludge fixed bed (UAFB), anoxic sink (AS) and aerobic membrane bioreactor (MBR). The hydraulic retention time of UAFB (HRTU) was gradually shortened from 8 h to 6 h, 3 h and to 1 h, while the HRT of AS and MBR kept at 8 h. It is found that HRTU of 3 h was more suitable for the balancing production of biogas and volatile fatty acids (VFAs), and the VFAs served as carbon source for denitrification. The trans-membrane pressure (TMP) of the MBR kept lower than 0.04 MPa without wash or change of membrane sheet, however, the scanning electron microscopy (SEM) analysis indicated that microbes attached to the inner-surface of membrane, causing irreversible fouling after 133-day operation. The denaturing gradient gel electrophoresis (DGGE) profiles of amplified 16S rDNA gene fragments proved that more functional bacteria and higher microbial diversity emerged at HRTU of 3 h and 1 h. Most bacteria belonged to Betaproteobacteria and were responsible for carbon and nitrogen removal.