Recent progress on the recovery of valuable resources from source-separated urine on-site using electrochemical technologies: A review

The rapid expanding of worldwide population and continuous advancement of living standard require increasing demand of resources, such as nutrients, water and energy, etc. From the viewpoint of circular economy and sustainable development, these resources often discarded as waste must be reclaimed and returned back to our daily life. Source-separated urine, one kind of the special decentralized wastewater, that contains a variety of nutrients with high concentration is considered as valuable waste stream. After being collected in the front-end, the urine can be treated on-site to recycle nutrients, energy and water. Among all the on-site treatment technologies, electrochemical technology is worth being paid more attention due to apparent advantages, including powerful news, flexibility and rapidness, as well as the potential to become intelligent technologies. As a niche technology, however, the electrochemical technology has been under-appreciated for a long time. In this review, the investigations and development of electrochemical technologies for nutrients recovery, energy exploitation and water reclamation in recent decade (2011–2021) are summarized and discussed systematically. The necessity to develop on-site treatment of source-separated urine was discussed initially. And then, pros and cons of each electrochemical technology to recover nutrients, energy and water, respectively, were discussed and analyzed. Perspective and future efforts on development of electrochemical technologies for the on-site treatment of urine were also carefully analyzed. Intelligent technology would become important part of the on-site electrochemical treatment of urine, aiming to optimize the treatment process, improve recovery efficiency and lower carbon footprint. This review is expected to open a new era for the investigation and development of electrochemical technologies towards on-site treatment of source-separated urine.