Strategies for Enhanced Performance of Wastewater Treatment in Membrane Bioreactors

Compared to conventional activated sludge systems, membrane bioreactors offer the advantages of achieving a very high effluent quality and eliminating the need for a sedimentation tank. In addition, pathogenic microbes are retained by the membrane, rendering the permeate largely germ free. The focus of the research was to further the use of membrane bioreactors as an option for wastewater treatment e.g. in rural areas. Membrane bioreactors in small scale are crossing the threshold towards a wider application. The main problem in the application of membrane bioreactors is membrane fouling. Therefore, the aim of the present study was to investigate the possibility of reducing fouling in membrane bioreactors for instance by air sparging. To analyze the behavior of a membrane bioreactor, synthetic wastewater was generated with dry milk powder simulating natural wastewater. The synthetic wastewater was stored in a concentrated form at about 4°C. The performance of a pilot scale membrane module (PCI Inc.) installed externally to the bioreactor was analyzed. The setup was assembled with a storage tank, commercially available membrane module, transparent hoses, pump (Grundfos), solenoid valves, air supply, pressure gauges and an electronic timer. The module is about 1.20 m in extension, fitted with five membrane tubes each 6 mm in diameter, pore-size 0.2 μm, yielding a membrane area of 0.1 m². The applied TMP (Trans-Membrane Pressure) was about 150 kPa and the cross flow velocity about 0.75 m/s. Simultaneous flow of water and air was secured by a solenoid valve. The valve safeguarded, that air was supplied only when the pump was running, to prevent membrane damage. The pump was connected to an electronic timer, which regulated intermittent pump work for energy saving purpose and longer equipment life.