Phosphorus recovery from wastewater through microbial processes

Waste streams offer a compelling opportunity to recover phosphorus (P). 15–20% of world demand for phosphate rock could theoretically be satisfied by recovering phosphorus from domestic waste streams alone. For very dilute streams (<10 mgP L−1), including domestic wastewater, it is necessary to concentrate phosphorus in order to make recovery and reuse feasible. This review discusses enhanced biological phosphorus removal (EBPR) as a key technology to achieve this. EBPR relies on polyphosphate accumulating organisms (PAOs) to take up phosphorus from waste streams, so concentrating phosphorus in biomass. The P-rich biosolids can be either directly applied to land, or solubilized and phosphorus recovered as a mineral product. Direct application is effective, but the product is bulky and carries contaminant risks that need to be managed. Phosphorus release can be achieved using either thermochemical or biochemical methods, while recovery is generally by precipitation as struvite. We conclude that while EBPR technology is mature, the subsequent phosphorus release and recovery technologies need additional development.

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► EBPR is a mature, effective technology to concentrate P from dilute streams.
► EBPR sludge is rich in phosphorus: it can be applied to land.
► Phosphorus in EBPR sludge can be recovered as struvite; P needs to first be solubilized.
► Solubilization of P through anaerobic digestion is attractive, but complexing with metal ions needs to be minimized.