Monitoring performance of a pilot two-stage anaerobic fluidized membrane bioreactor (AFMBR)

A pilot-scale two-stage anaerobic fluidized membrane bioreactor (AFMBR) treating settled raw municipal wastewater (24 m3/day) was operated at Ulu Pandan Water Reclamation Plant, Singapore. The first stage was an anaerobic fluidized bed reactor (AFBR) followed by two parallel fluidized bed membrane bioreactors, namely flat sheet and hollow fibre AFMBR as the second stage respectively. This study was conducted to examine the reactor and membrane performances, biogas production, and energy consumption of each two-stage AFMBR. The reactor and membrane performances of the pilot AFMBR were evaluated in this study. More than 87% of total chemical oxygen demand (COD), 69% of soluble COD, 81% of total organic carbon (TOC), and almost 100% of total suspended solids (TSS) were removed in the two-stage AFMBR, almost regardless of membrane configuration. However, slightly better removal efficiencies were observed in the hollow fibre system. In detail, on an average, the first-stage AFBR effectively removed 37% of total COD, 42% of soluble COD, 49% of TOC, and 38% of TSS, while the attached-biofilm on the GAC particles in the second-stage AFMBR further removed some of the residual soluble organics at a ratio of 18% of total COD, and 17% of soluble COD, 23% of TOC, and 31% of TSS in hollow fibre AFMBR and 27% of total COD, 20% of soluble COD, 25% of TOC, and 34% of TSS in flat sheet AFMBR. The transmembrane pressure was recorded daily and an averaged value of 0.21 bar and 0.08 bar was observed for hollow fibre and flat sheet AFMBR respectively at a designed membrane flux of 5.5 L/m2.h. The transmembrane pressure was considerably lower than the maximum allowable value (0.3 bar), which indicated that membrane fouling was negligible. In addition, total carbon balance was performed for the two-stage AFMBR. Gaseous methane production was the largest with a COD conversion of 42.6% while only 23.4% of COD was converted to dissolved methane. Lastly, the energy consumption was evaluated and the calculated energy required for two-stage hollow fibre and flat sheet AFMBR was 0.136 kWh/m3 and 0.151 kWh/m3 respectively. The energy produced by gaseous methane was 0.045 kWh/m3 and 0.061 kWh/m3 for two-stage hollow fibre and flat sheet AFMBR respectively, which could only satisfy 33% of the energy required.Bachelor of Engineering (Environmental Engineering