Integrated processes for simultaneous nitrogen, phosphorus, and potassium recovery from urine: A review

Urine, traditionally regarded as liquid waste, contains valuable elements – nitrogen (N), phosphorus (P), and potassium (K) which can be repurposed as crop fertilizers. Under the context of dwindling resources, recent researches have concentrated on the development of advanced methods recovering valuable compounds from urine. This review explores urine concentration technologies for recovering N, P, and K fertilizers from urine, including alkaline dehydration, forward osmosis, membrane distillation, and freeze concentration. Furthermore, the paper focuses on advanced technologies, combined systems, and simultaneous recovery sequences tailored to different application scenarios for recovering specific nutrient elements (N, P, and K) simultaneously. In contrast to other relevant articles on urine nutrient recovery, this study provides a thorough overview of key technologies for nitrogen, phosphorus, and potassium recovery from urine, offering diverse recovery process options based on specific recycling needs. The central focus of this paper lies in the systematic integration of diverse technologies to achieve the simultaneous recovery of multiple resources from urine. It delves into optimal recovery sequences and process coupling strategies for individual recoveries. In summary, this paper presents innovative strategies for the simultaneous recovery of N, P, and K in urine, addressing the pressing need for sustainable resource management.