Membrane bioreactor (MBR) has received much technology innovation and development in the past decade. Nevertheless, applications of this technology are still limited due to its high capital and operational costs. In order to reduce the costs significantly, this study was motivated to develop a low-cost MBR by using coarse-pore membrane. Nylon mesh material with a mean pore size of 53 μm was selected as the coarse-pore membrane in this study. The objective of this study was to develop this MBR into a continuous-flow bioreactor with in-situ membrane cleaning mechanism as well as evaluate the performance of this system....[ Read more ]

Membrane bioreactor (MBR) has received much technology innovation and development in the past decade. Nevertheless, applications of this technology are still limited due to its high capital and operational costs. In order to reduce the costs significantly, this study was motivated to develop a low-cost MBR by using coarse-pore membrane. Nylon mesh material with a mean pore size of 53 μm was selected as the coarse-pore membrane in this study. The objective of this study was to develop this MBR into a continuous-flow bioreactor with in-situ membrane cleaning mechanism as well as evaluate the performance of this system.

A flat-type membrane module was developed with the nylon mesh, which was installed in a lab-scale set-up for a feasibility study. Effectiveness of the in-situ membrane cleaning by air scoring and the off-tank membrane cleaning by immersing the membrane into a 1-% wt. sodium hypochloride solution was examined. A 10-min in-situ membrane cleaning was conducted twice per day with an air supply rate of 20 L/min. This cleaning measure enabled continuous-flow operation of the system up to 23 days at a permeate flux of 1.7 m³/m²·day and MLSS of 4,500 mg/L without the off-tank cleaning of the membrane. Comparatively, suspension of the in-situ cleaning shortened the operation in 48 hrs only. The SEM analysis demonstrated that both physical and chemical cleaning methods could reduce the fouling problem effectively.

Performance of a lab-scale MBR with the developed membrane module was evaluated by continuously feeding synthetic wastewater with TOC 100 mg/L and TN 30 mg/L. The system operated for 137 days under the following conditions: MLSS concentration 4,500 mg/L, HRT 12 – 14 hrs, F/M ratio 1.3 and permeate flux 1.71 m³/m²·day, respectively. The developed MBR could produce good effluent quality (SS: 13-22 mg/L, turbidity: 4-12 NTU). The TOC removal efficiency was higher than 93%. The maximally acceptable levels of MLSS concentration and permeate flux could be up to 6,000 mg/L and 2.8 m³/m²·day, respectively.

Keywords

Low-cost MBR; coarse-pore membrane; nylon mesh membrane module; membrane cleaning; continuous-flow operation.