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Updated: Jul 11, 2026
08:13
A Novel Bioreactor for High Density Cultivation of Diverse Microbial Communities
Published on: December 25, 2015
Design and performance of BNR activated sludge systems with flat sheet membranes for solid-liquid separation
G J G du Toit1, M C Ramphao, V Parco
1Water Research Group, University of Cape Town, 7700, RSA, South Africa. geoff.dutoit@shands.co.za
Summary
Membrane bioreactors (MBRs) in biological nutrient removal activated sludge (BNRAS) systems offer superior or equivalent removal of pollutants like COD, TKN, and TSS compared to conventional systems. MBRs also show enhanced phosphorus removal due to specific operational conditions.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Biotechnology
Background:
- Biological Nutrient Removal Activated Sludge (BNRAS) systems are crucial for wastewater treatment.
- Conventional BNRAS systems often face limitations in solid-liquid separation.
- Membrane filtration offers an alternative for enhanced solid-liquid separation in BNRAS.
Purpose of the Study:
- To compare the performance of Membrane Bioreactor (MBR) systems with conventional activated sludge systems for BNRAS.
- To investigate the influence of immersed membranes on system response and pollutant removal efficiency.
- To quantify the impact of membranes on nutrient removal (COD, FSA, TKN, TP, TSS).
Main Methods:
- Laboratory-scale investigation of two parallel BNRAS systems: one MBR and one conventional.
- Both systems utilized a three-reactor anaerobic, anoxic, aerobic University of Cape Town (UCT) configuration.
- Identical design parameters (reactor mass fractions, recycles, sludge age) were maintained, with variations in influent flow, reactor volumes, and concentrations.
Main Results:
- The MBR UCT system demonstrated consistently equivalent or superior removal of COD, FSA, TKN, TP, and TSS compared to the conventional system.
- Improved phosphorus (P) removal in the MBR was linked to reduced P uptake in the anoxic zone, influenced by high nitrate loads.
- The MBR system exhibited higher sludge production due to complete solids retention.
Conclusions:
- Immersed membranes in BNRAS systems provide comparable or enhanced pollutant removal efficiencies.
- MBR technology offers advantages in phosphorus removal under specific operational conditions.
- Increased sludge production in MBRs needs to be accounted for in steady-state design by adjusting influent parameters.
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