Resource recovery from sulphate-rich sewage through an innovative anaerobic-based water resource recovery facility...

This research work proposes an innovative water resource recovery facility (WRRF) for the recovery of energy, nutrients and reclaimed water from sewage, which represents a promising approach towards enhanced circular economy scenarios. To this aim, anaerobic technology, microalgae cultivation, and membrane technology were combined in a dedicated platform. The proposed platform produces a high-quality solid- and coliform-free effluent that can be directly discharged to receiving water bodies identified as sensitive areas. Specifically, the content of organic matter, nitrogen and phosphorus in the effluent was 45 mg COD·L^-1, 14.9 mg N·L^-1 and 0.5 mg P·L^-1, respectively. Harvested solar energy and carbon dioxide biofixation in the form of microalgae biomass allowed remarkable methane yields (399 STP L CH₄·kg^-1 COD_inf) to be achieved, equivalent to theoretical electricity productions of around 0.52 kWh per m³ of wastewater entering the WRRF. Furthermore, 26.6% of total nitrogen influent load was recovered as ammonium sulphate, while nitrogen and phosphorus were recovered in the biosolids produced (650 ± 77 mg N·L^-1 and 121.0 ± 7.2 mg P·L^-1).