Operational factors of submerged inorganic membrane bioreactor for organic wastewater treatment: sludge concentration and aeration rate

Abstract

Various sludge concentrations and aeration rates were evaluated to find the optimal operation condition of a submerged ceramic membrane filtration system. 5.6 g/L of sludge was diluted with water to concentrations of 2.8 g/L and 1.4 g/L, and the three sludge concentrations were compared in terms of titration characteristics such as pressure and filtrate flux. Flux was at the highest value of about 30 L/m2 x hr at 50 kPa when sludge concentration was 1.4 g/L. In contrast, when sludge concentrations increased to 2.8 g/L and 5.6 g/L, the flux at 50 kPa decreased significantly to 18 L/m2 x hr and 10 L/m2 x hr, respectively. It was concluded that the sludge concentration directly affected the filtration efficiency, and low sludge concentration was suitable for improving filtration efficiency. Adjusting the aeration rate from 2 L/min to 4 L/min at 5.6 g/L of sludge and 50 kPa of pressure increased flux from 10 L/m2 x hr to 13 L/m2 x hr. It was obvious that the vigorous aeration improved the filtration efficiency, but the aeration rate did not seem to be high enough to maintain flux lower than critical flux.

Biomass characteristics and membrane aeration: Toward a better understanding of membrane fouling in submerged membrane bioreactors (MBRs)

“…Gui et al (2003) explained the sharp increase in TMP above this transitional value by particles starting to deposit on the membrane; below this value no particle deposition was noticed. Hwang et al (2003) found that membrane fouling was reduced at a low solids concentration of 1.4 g.L À1 and Le Clech et al (2003) noticed no significant difference in the critical flux when the solids concentrations was increased from 4 to 8 g.L À1 . Table II.…”

Membrane Fouling of Submerged Membrane Bioreactors: Impact of Mean Cell Residence Time and the Contributing Factors

“…Effect of MLSS, CST, and Biomass ζ Potential on Membrane Fouling. Several researchers (5,(20)(21) had reported that high MLSS concentration will increase the membrane filtration resistance. This study, however, demonstrated that the 3-day MCRT MBR, despite having the lowest MLSS concentration, experienced the highest membrane fouling rate among the four MBRs studied.…”

Diverse and Distinct Bacterial Communities Induced Biofilm Fouling in Membrane Bioreactors Operated under Different Conditions

“…While full-scale MBRs are typically operated at relatively long SRTs to reduce reactor footprint and minimize excess sludge, some wastewater treatment plants could prefer a short SRT operation to maximize sludge production for biogas generation. Although it was originally believed that high MLSS concentration associated with long SRT operation will increase membrane filtration resistance − , recent studies have revealed that MBRs operated at low SRT (or high F/M ratio) exhibited faster membrane fouling rates , . Likewise, biofilm formation and membrane fouling occurred earlier and faster in MBR-8 which was operated at a much higher F/M ratio.…”