Performance evaluation of the bench-scale hybrid alternating aerobic/anoxic activated sludge-membrane bioreactor system for the wastewater treatment and reuse

In this study, the effect of total dissolved solids (TDS) on the simultaneous removal of TDS and biological nitrogen was investigated in a bench-scale hybrid alternating aerobic/anoxic activated sludge-membrane bioreactor (AAA-MBR). The aerobic granular sludge was cultivated in an aerobic sequencing batch reactor with municipal wastewater (organic loading rate: 2.1−4.3 kg COD/m³ day) and used as a biosorbent for TDS removal in the pretreatment reactor. The AAA-MBR system, consisting of two AAA zones and a reaction zone where the membrane modules are submerged, was operated for 30 d under four TDS conditions (average TDS concentrations of 0, 2,003, 3,003, and 4,032 mg/L for Phase I, II, III, and IV, respectively). The influent wastewater was synthesized to simulate the reverse osmosis concentrate (ROC) obtained from a full-scale municipal wastewater reclamation plant that recycles secondary sewage effluents. The reduction efficiency of the chemical oxygen demand (COD) (>98.8% removal) and rate of nitrification (>93.9%) and denitrification (>86.1%) were not significantly influenced by the TDS concentration (<2,003 mg/L) of the influent. Thus, the AAA-MBR process could be an effective ROC recycling alternative to the conventional methods to reduce TDS content, COD, and biological nitrogen at a low cost with less consumption of chemical adsorbents or coagulants.