A critical review on phosphorus recovery from source-diverted blackwater

Source-diverted blackwater refers to toilet wastewater, sometimes including kitchen wastewater, which is rich in essential nutrients such as nitrogen (N) and phosphorus (P). Blackwater, especially concentrated blackwater collected from low-flush vacuum toilet systems, represents a valuable source for P recovery, addressing future P scarcity and mitigating environmental issues like eutrophication. While there has been growing interest in technologies for P recovery from blackwater, these technologies are still in the early stages of development. This study provides a comprehensive review of the mechanisms behind phosphate salt formation, the technologies for P recovery from blackwater-particularly through struvite and calcium phosphate precipitation-and the safety concerns associated with the use of recovered products. Despite advancements, most research is limited to lab-scale experiments, leaving significant gaps in optimizing P recovery technologies for broader application. Future research will be likely to focus on integrating bioenergy recovery with P recovery in anaerobic digestion (AD) systems, aiming to create a more sustainable and zero-waste approach. Addressing current challenges and scaling up from lab research to real-world applications will be crucial for making P recovery more efficient and economically viable.