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Source separation and treatment of human urine have been recognized as a resource-efficient alternative to conventional urban drainage, not only reducing nutrient loads on municipal wastewater treatment plants, but recovering valuable resources from waste streams. In this work, on-site phosphorus (P) recovery from real urine was carried out by using the brine from a reverse osmosis process as the flush water for urine-diverting toilets and a P precipitant, while nitrogen (N) was removed via short-cut nitrification-denitrification (SCND) in a membrane bioreactor (MBR). More than 90% of P was recovered by mixing the urine with reverse osmosis brine (1:1, v/v) under the condition of pH > 9.0. The recovered precipitates contained 10-15% of P and can potentially be reused for phosphate fertilizer production. Stable SCND was achieved in a MBR, and 45% of N was removed with the organic compounds in urine as the electron donor for denitrification. Methanol addition significantly elevated denitrification, which in turn replenished the alkalinity required for nitrification. More than 99% of P, 90% of organics and 90% of N were removed in the combined precipitation and MBR process. Nitrosomonas was observed to be the predominant ammonium-oxidizing bacteria, while nitrite-oxidizing bacteria (NOB) were absent in the microbial communities as revealed by fluorescence in situ hybridization and pyrosequencing technique. High concentrations of free ammonia and nitrite acids, as well as low dissolved oxygen, are the prevailing factors to inhibit the growth of NOB, which allows for stable operation of SCND in the MBR., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Phosphorus (P) recovery from waste streams has recently been recognized as a key step in the sustainable supply of this indispensable and non-renewable resource. The feasibility of using brine from a reverse osmosis (RO) membrane unit treating cooling water as a precipitant for P recovery from source separated urine was evaluated in the present study. P removal efficiency, process parameters and precipitate properties were investigated in batch and continuous flow experiments. More than 90% of P removal was obtained from both undiluted fresh and hydrolyzed urines by mixing with RO brine (1:1, v/v) at a pH over 9.0. Around 2.58 and 1.24 Kg of precipitates could be recovered from 1 m 3 hydrolyzed and fresh urine, respectively, and the precipitated solids contain 8.1-19.0% of P, 10.3-15.2% of Ca, 3.7-5.0% of Mg and 0.1-3.5% of ammonium nitrogen. Satisfactory P removal performance was also achieved in a continuous flow precipitation reactor with a hydraulic retention time of 3-6 h. RO brine could be considered as urinal and toilet flush water despite of a marginally higher precipitation tendency than tap water. This study provides a widely available, low - cost and efficient precipitant for P recovery in urban areas, which will make P recovery from urine more economically attractive., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Phosphorus (P) recovery from wastewater has been recognized as a critical technology for solving the sustainable supply of this indispensable and non - renewable natural resource. In this study, the cost - free magnesium and calcium sources of using the cooling water system effluent (CWSE) in two thermal power plants were proposed (Z - CWSE and G - CWSE) and the P recovery performance from source - separated urine was investigated. About 90% P recovery efficiency was achieved from the hydrolyzed urine when Z - CWSE and G - CWSE were added at the Ca: Mg: P molar ratios of 3.1 : 4.0: 1 and 3.6 : 3.4: 1, respectively. More than 95% P recovery performance was obtained from the fresh urine as the initial pH of the CWSE - FU mixtures was adjusted to over 9.5 and 10.0, respectively. The precipitates obtained contain 10.84–17.04% Ca, 6.22–9.58% P, 0.75–3.76% Mg and 0.13–0.23% N. XRD analysis confirmed the presence of struvite in the precipitates. The reuse of precipitates is secure due to extremely low contents of heavy metals. The feasibility of using CWSEs as the flushing water in urinals and toilets was assessed. Besides, we proposed CWSEs could be invoked as precipitants in various wastewaters as long as it contains considerable phosphate, e.g. P concentration more than 100 mg/L and 50 mg/L for Z - CWSE and G - CWSE, respectively. • CWSEs are effective magnesium and calcium sources for P recovery from urine. • 90–95% P was recovered from urine at the CWSEs/urine of 2.5:1 (v/v) at pH > 9.0. • Precipitates contain 6.22–9.58% P and no harmful heavy metals are detected. • CWSEs can be potentially used as urinal and toilet flushing water. • CWSEs can be used to recover P from wastewaters contained >50 mg P/L. [ABSTRACT FROM AUTHOR]

Abstract Separation and treatment of human urine from domestic wastewater have been recognized as a sustainable alternative to conventional urban sanitation system, but the unique water quality of source-separated urine, such as high nutrient, insufficient alkalinity and low COD/nitrogen ratio, poses challenges to the biological nitrogen removal process. It was hypothesized that a physicochemical pre-treatment should be adopted to not only reduce nitrogen load but adjust water quality suitable for biological treatment. In this study, a vacuum thermal stripping process coupled to acid absorption was used as a pre-treatment to recover ammonia from hydrolyzed urine in the form of ammonium sulphate. The maximal ammonia mass transfer coefficient of 17.6 mm/h was obtained under 60 °C and 21.3 kPa 80% of the nitrogen in hydrolyzed urine was recovered in 3 h batch stripping experiments without pH adjustment, corresponding to a nitrogen recovery loading rate of 36 kg N/m3⋅d. The majority of organic matters were retained in urine solutions, thus COD/N and alkalinity/NH 4 + N ratios were elevated to 4.75 and 4.37, respectively. Phosphorus recovery could be simultaneously obtained in stripping process by adding MgCl 2. The remaining nitrogen was effectively removed via short-cut nitrification and denitrification in an anoxic/oxic membrane bioreactor. More than 95% of overall nutrient recovery/removal from urine was achieved with a minimal consumption of external resources. The economic assessment of the technique showed that the recovery/removal of nutrients from 1 m3 of urine can make a profit of € 0.26. Graphical abstract Image 1 Highlights • Vacuum thermal stripping (VTS) was used to recover N from source-separated urine. • VTS recovered 80% N and adjusted C/N and alkalinity/N ratios in urine solution. • No external C source was required for biological N removal. • Over 95% P and N recovery/removal was achieved. [ABSTRACT FROM AUTHOR]