Center for Microbial Ecology and Technology (CMET), Department of Biotechnology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium.
Departament d'Enginyeria Química, Biològica I Ambiental, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Bellaterra 08193 Barcelona, Spain.
Environ Sci Technol. 2021 Jun 15;55(12):8287-8298. doi: 10.1021/acs.est.1c00041. Epub 2021 Jun 4.
Urine is a valuable resource for nutrient recovery. Stabilization is, however, recommended to prevent urea hydrolysis and the associated risk for ammonia volatilization, uncontrolled precipitation, and malodor. This can be achieved by alkalinization and subsequent biological conversion of urea and ammonia into nitrate (nitrification) and organics into CO. Yet, without pH control, the extent of nitrification is limited as a result of insufficient alkalinity. This study explored the feasibility of an integrated electrochemical cell to obtain on-demand hydroxide production through water reduction at the cathode, compensating for the acidification caused by nitritation, thereby enabling full nitrification. To deal with the inherent variability of the urine influent composition and bioprocess, the electrochemical cell was steered via a controller, modulating the current based on the pH in the bioreactor. This provided a reliable and innovative alternative to base addition, enabling full nitrification while avoiding the use of chemicals, the logistics associated with base storage and dosing, and the associated increase in salinity. Moreover, the electrochemical cell could be used as an in situ extraction and concentration technology, yielding an acidic concentrated nitrate-rich stream. The make-up of the end product could be tailored by tweaking the process configuration, offering versatility for applications on Earth and in space.
尿液是一种有价值的营养物质回收资源。然而，为了防止尿素水解和由此产生的氨挥发、不受控制的沉淀和恶臭风险，建议对其进行稳定化处理。这可以通过碱化以及随后将尿素和氨生物转化为硝酸盐（硝化），将有机物转化为 CO 来实现。然而，如果没有 pH 控制，由于碱度不足，硝化的程度会受到限制。本研究探索了集成电化学电池的可行性，通过在阴极还原水来按需产生氢氧根，补偿亚硝化引起的酸化，从而实现完全硝化。为了应对尿液进水成分和生物工艺的固有可变性，电化学电池通过控制器进行控制，根据生物反应器中的 pH 值调节电流。这为添加碱提供了一种可靠且创新的替代方案，实现了完全硝化，同时避免了使用化学品、与碱储存和投加相关的物流以及相关的盐度增加。此外，电化学电池可用作原位提取和浓缩技术，产生酸性浓缩的富含硝酸盐的流。通过调整工艺配置，可以调整最终产品的组成，为地球和太空应用提供多功能性。
