Phosphate recovery as struvite within a single chamber microbial electrolysis cell

[Display omitted] . ► Phosphorus was successfully precipitated as struvite at the cathode of a MESC. ► Soluble phosphorous removal reached 40% at electrical efficiencies well above 100%. ► H2 production rates were not affected by struvite precipitation. ► Concurrent H2 and struvite precipitation could substantially lower production costs. An energy efficient method of concurrent hydrogen gas and struvite (MgNH4PO4·6H2O) production was investigated based on bioelectrochemically driven struvite crystallization at the cathode of a single chamber microbial electrolysis struvite-precipitation cell (MESC). The MESC cathodes were either stainless steel 304 mesh or flat plates. Phosphate removal ranged from 20% to 40%, with higher removals obtained using mesh cathodes than with flat plates. Cathode accumulated crystals were verified as struvite using a scanning electron microscope capable of energy dispersive spectroscopy (SEM–EDS). Crystal accumulation did not affect the rate of hydrogen production in struvite reactors. The rate of struvite crystallization (g/m2-h) and hydrogen production (m3/m3-d) were shown to be dependent on applied voltage and cathode material. Overall energy efficiencies (substrate and electricity) were high (73±4%) and not dependent on applied voltage. These results show that MESCs may be useful both as a method for hydrogen gas and struvite production.