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Alkaline Dehydration of Human Urine Collected in Source-Separated Sanitation Systems Using Magnesium Oxide
Frontiers in Environmental Science ( IF 3.3 ) Pub Date : 2021-01-20 , DOI: 10.3389/fenvs.2020.619901
Prithvi Simha , Christopher Friedrich , Dyllon Garth Randall , Björn Vinnerås

Fresh human urine, after it is alkalized to prevent the enzymatic hydrolysis of urea, can be dehydrated to reduce its volume and to produce a solid fertilizer. In this study, we investigated the suitability of MgO to alkalize and dehydrate urine. We selected MgO due to its low solubility (<2 g·L−1) and relatively high saturation pH (9.9 ± 0.2) in urine. Using a laboratory-scale setup, we dehydrated urine added to pure MgO and MgO mixed with co-substrates (biochar, wheat bran, or calcium hydroxide) at a temperature of 50°C. We found that, dehydrating urine added to a mixture of MgO (25% w/w), biochar, and wheat bran resulted in a mass reduction of >90% and N recovery of 80%, and yielded products with high concentrations of macronutrients (7.8% N, 0.7% P and 3.9% K). By modeling the chemical speciation in urine, we also showed that ammonia stripping rather than urea hydrolysis limited the N recovery, since the urine used in our study was partially hydrolyzed. To maximize the recovery of N during alkaline urine dehydration using MgO, we recommend treating fresh/un-hydrolysed urine a temperature <40°C, tailoring the drying substrate to capture NH 4 + as struvite, and using co-substrates to limit the molecular diffusion of ammonia. Treating fresh urine by alkaline dehydration requires only 3.6 kg MgO cap−1y−1 and a cost of US$ 1.1 cap−1y−1. Therefore, the use of sparingly soluble alkaline compounds like MgO in urine-diverting sanitation systems holds much promise.

中文翻译:

使用氧化镁对在源头分离的卫生系统中收集的人类尿液进行碱性脱水

新鲜的人尿经过碱化以防止尿素酶水解后,可以脱水以减少其体积并产生固体肥料。在这项研究中,我们调查了 MgO 碱化尿液和脱水尿液的适用性。我们选择 MgO 是因为它在尿液中的溶解度低 (<2 g·L−1) 和相对较高的饱和 pH (9.9 ± 0.2)。使用实验室规模的设置,我们在 50°C 的温度下将添加到纯 MgO 和 MgO 与共底物(生物炭、麦麸或氢氧化钙)混合的尿液脱水。我们发现,将脱水尿液添加到 MgO (25% w/w)、生物炭和麦麸的混合物中导致质量减少 >90% 和 N 回收率为 80%,并产生具有高浓度常量营养素的产品( 7.8% N、0.7% P 和 3.9% K)。通过模拟尿液中的化学形态,我们还表明氨汽提而不是尿素水解限制了 N 的回收,因为我们研究中使用的尿液是部分水解的。为了在使用 MgO 的碱性尿液脱水过程中最大限度地回收 N,我们建议在 <40°C 的温度下处理新鲜/未水解的尿液,调整干燥底物以将 NH 4 + 捕获为鸟粪石,并使用共底物来限制分子氨的扩散。通过碱性脱水处理新鲜尿液仅需要 3.6 kg MgO cap−1y−1 和 1.1 美元 cap−1y−1 的成本。因此,在尿液分流卫生系统中使用微溶碱性化合物(如 MgO)很有希望。我们建议在 <40°C 的温度下处理新鲜/未水解的尿液,调整干燥基质以将 NH 4 + 捕获为鸟粪石,并使用共基质来限制氨的分子扩散。通过碱性脱水处理新鲜尿液仅需要 3.6 kg MgO cap−1y−1 和 1.1 美元 cap−1y−1 的成本。因此,在尿液分流卫生系统中使用微溶碱性化合物(如 MgO)很有希望。我们建议在 <40°C 的温度下处理新鲜/未水解的尿液,调整干燥基质以将 NH 4 + 捕获为鸟粪石,并使用共基质来限制氨的分子扩散。通过碱性脱水处理新鲜尿液仅需要 3.6 kg MgO cap−1y−1 和 1.1 美元 cap−1y−1 的成本。因此,在尿液分流卫生系统中使用微溶碱性化合物(如 MgO)很有希望。
更新日期:2021-01-20
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