Abstract
Municipal wastewater has been identified as a potential source of natural phosphorus (P) that is projected to become depleted in a few decades based on current exploitation rates. This paper focuses on combining a bench-scale anaerobic/anoxic/aerobic membrane bioreactor (MBR) and magnesium carbonate (MgCO3)-based pellets to effectively recover P from municipal wastewater. Ethanol was introduced into the anoxic zone of the MBR system as an external carbon source to improve P release via the enhanced biological phosphorus removal (EBPR) mechanism, making it available for adsorption by the continuous-flow MgCO3 pellet column. An increase in the concentration of P in the MBR effluent led to an increase in the P adsorption capacity of the MgCO3 pellets. As a result, the anaerobic/anoxic/aerobic MBR system, combined with a MgCO3 pellet column and ethanol, achieved 91.6% P recovery from municipal wastewater, resulting in a maximum P adsorption capacity of 12.8 mg P/g MgCO3 through the continuous-flow MgCO3 pellet column. Although the introduction of ethanol into the anoxic zone was instrumental in releasing P through the EBPR, it could potentially increase membrane fouling by increasing the concentration of extracellular polymeric substances (EPSs) in the anoxic zone.
Highlights
Natural phosphorus (P) reserves will be depleted in a few decades if the phosphorus fertilizer demand increases at 3% per year [1]
In Phase 5 (i.e., 100% of the membrane bioreactor (MBR) effluent was withdrawn from the polyvinylidene fluoride (PVDF) membrane submerged in the aerobic zone), we introduced the MBR effluent into the MgCO3 pellet column for P recovery
The hydraulic retention times (HRTs) decreased from 16 h (Phase 1) to 8 h (Phase 3), the chemical oxygen demand (COD) concentration in the MBR effluent ranged between 2.5 and 4.5 mg/L (>97% removal)
Summary
Natural phosphorus (P) reserves will be depleted in a few decades if the phosphorus fertilizer demand increases at 3% per year [1]. Municipal wastewater has been identified as an alternative P source that potentially reduces natural P extraction from phosphate rocks [2]. It has been estimated that 15–20% of the world’s phosphorus demand could be satisfied by its recovery from municipal wastewater [1,3,4]. A recent study showed that humans discharge about 3.7 Mt of P into wastewater, making its recovery from wastewater a desirable alternative capable of providing sustainable phosphorus supplies that could supplement natural phosphorus [4]. This essential element (i.e., P) in sewage can be recovered through chemical precipitation, biological processes, physical adsorption, sewage sludge, wetland plants, and wastewater irrigation. Physical adsorption, and biological removal using the enhanced biological phosphorus removal (EBPR) mechanism are the most widely used methods [5]
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