2.1. AFMBR Operation

A laboratory-scaled AFMBR system was developed as shown in Figure 1 and applied in this study. The reactor was made using acrylic materials with a total reactor volume of 4 L. A flat-tubular ceramic membrane consisting of alumina dioxide with a pore size of 0.5 um and an effective area of 0.1 m² was applied. The membrane was submerged into the AFMBR and operated by a peristaltic pump (Green Tech, GT-150d, Suwon-si, Korea) at constant permeate flux. A sedimentation tank was installed at the upper part of the membrane reactor to prevent the fluidized media from entering into the recirculation pump (PAN WORLD, NH-150S, Ibaraki-ken, Japan). A recirculation pump was installed at the bottom of the reactor for recirculating bulk suspension from the top of the settling tank to the bottom of the membrane reactor to allow both media to be fluidized along the membrane surface at 3 L/min (0.028 m/s). Synthetic feed wastewater was prepared by using sodium acetate and sodium propionate with 300 mg/L of chemical oxygen demand (COD). The 30 mg/L of ammonium nitrogen and 1 mg/L of phosphate was prepared by using ammonium chloride and potassium phosphate, respectively. Sodium bicarbonate with 100 mg/L was injected into a feed solution to maintain a neutral pH. A level sensor was installed to maintain the water level in the reactor by controlling the feed pump. The reactor was seeded by adding 200 mL of biomass, which is taken from the anaerobic digester operated at the local sewage treatment plant. A Supernatant was added with a 100 mL volume of 1% v/v into a feed tank to provide trace nutrients for the growth of microorganisms. A Tedlar bag was installed at the top of the reactor to collect biogas produced by AFMBR operated at room temperature.

Schematic diagram of AFMBR with the dual media process.