Refinery and concentration of nutrients from urine with electrodialysis enabled by upstream precipitation and nitrification. (1st November 2018)

• Record Type: Journal Article
• Authors: De Paepe, Jolien; Lindeboom, Ralph E.F.; Vanoppen, Marjolein; De Paepe, Kim; Demey, Dries; Coessens, Wout; Lamaze, Brigitte; Verliefde, Arne R.D.; Clauwaert, Peter; Vlaeminck, Siegfried E.
• Is Part Of: Water research. Volume 144(2018)
• Page Start: 76
• Page End: 86
• Publication Date: 2018-11-01
• Subjects: Source separation -- Resource recovery -- MBBR -- MBR -- Electrodialysis; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2018.07.016
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Human urine is a valuable resource for nutrient recovery, given its high levels of nitrogen, phosphorus and potassium, but the compositional complexity of urine presents a challenge for an energy-efficient concentration and refinery of nutrients. In this study, a pilot installation combining precipitation, nitrification and electrodialysis (ED), designed for one person equivalent (1.2 Lurine d −1 ), was continuously operated for ∼7 months. First, NaOH addition yielded calcium and magnesium precipitation, preventing scaling in ED. Second, a moving bed biofilm reactor oxidized organics, preventing downstream biofouling, and yielded complete nitrification on diluted urine (20–40%, i.e. dilution factors 5 and 2.5) at an average loading rate of 215 mg N L −1 d −1 . Batch tests demonstrated the halotolerance of the nitrifying community, with nitrification rates not affected up to an electrical conductivity of 40 mS cm −1 and gradually decreasing, yet ongoing, activity up to 96 mS cm −1 at 18% of the maximum rate. Next-generation 16S rRNA gene amplicon sequencing revealed that switching from a synthetic influent to real urine induced a profound shift in microbial community and that the AOB community was dominated by halophilic species closely related to Nitrosomonas aestuarii and Nitrosomonas marina . Third, nitrate, phosphate and potassium in the filtered (0.1 μm) bioreactor effluent were concentrated by factors 4.3, 2.6 and 4.6, respectively, with ED. Doubling the urine concentration from 20% to 40% further increased the ED recovery efficiency by ∼10%. Batch experiments at pH 6, 7 and 8 indicated a more efficient phosphate transport to the concentrate at pH 7. The newly proposed three-stage strategy opens up opportunities for energy- and chemical-efficient nutrient recovery from urine. Precipitation and nitrification enabled the long-term continuous operation of ED on fresh urine requiring minimal maintenance, which has, to the best of our knowledge, never been achieved before. Graphical abstract: Image 1 Highlights: Pre-treatment enables ED operation on real urine with minimal scaling & biofouling. 64–70% of N, 54–67% of P, 70–83% of K was captured in 15–20% of the initial volume. Base dosage for precipitation equally lowered base demand for full nitrification. More than 90% and 95% of incoming COD and urea were converted at 10–20 mS cm −1 . Nitrifying sludge cultivated at 10 mS cm −1 still demonstrated activity >90 mS cm −1 .