Wetsus , European Centre of Excellence for Sustainable Water Technology , P.O Box 1113, 8900CC Leeuwarden , The Netherlands.
Sub-Department of Environmental Technology , Wageningen University , P.O. Box 17, 6700AA Wageningen , The Netherlands.
Environ Sci Technol. 2018 Nov 20;52(22):13144-13154. doi: 10.1021/acs.est.8b03502. Epub 2018 Oct 31.
Simultaneous recovery of calcium phosphate granules (CaP granules) and methane in anaerobic treatment of source separated black water (BW) has been previously demonstrated. The exact mechanism behind the accumulation of calcium phosphate (Ca (PO) ) in CaP granules during black water treatment was investigated in this study by examination of the interface between the outer anaerobic biofilm and the core of CaP granules. A key factor in this process is the pH profile in CaP granules, which increases from the edge (7.4) to the center (7.9). The pH increase enhances supersaturation for Ca (PO) phases, creating internal conditions preferable for Ca (PO) precipitation. The pH profile can be explained by measured bioconversion of acetate and H, HCO and H into CH in the outer biofilm and eventual stripping of CO and CH (biogas) from the granule. Phosphorus content and Ca (PO) crystal mass quantity in the granules positively correlated with the granule size, in the reactor without Ca addition, indicating that the phosphorus rich core matures with the granule growth. Adding Ca increased the overall phosphorus content in granules >0.4 mm diameter, but not in fine particles (<0.4 mm). Additionally, H released from aqueous phosphate species during Ca (PO) crystallization were buffered by internal hydrogenotrophic methanogenesis and stripping of biogas from the granule. These insights into the formation and growth of CaP granules are important for process optimization, enabling simultaneous Ca (PO) and CH recovery in a single reactor. Moreover, the biological induction of Ca (PO) crystallization resulting from biological increase of pH is relevant for stimulation and control of (bio)crystallization and (bio)mineralization in real environmental conditions.
先前已经证明，在分离源黑水（BW）的厌氧处理中，可以同时回收磷酸钙颗粒（CaP 颗粒）和甲烷。在这项研究中，通过检查外厌氧生物膜和 CaP 颗粒核心之间的界面，研究了在 BW 处理过程中 CaP 颗粒中磷酸钙（Ca（PO））积累的确切机制。这一过程的一个关键因素是 CaP 颗粒中的 pH 分布，从边缘（7.4）增加到中心（7.9）。pH 值的增加增强了 Ca（PO）相的过饱和度，为 Ca（PO）沉淀创造了内部条件。pH 值分布可以通过测量外生物膜中乙酸和 H、HCO 和 H 转化为 CH，以及最终从颗粒中脱除 CO 和 CH（沼气）来解释。在没有 Ca 加入的反应器中，颗粒中磷含量和 Ca（PO）晶体质量与颗粒尺寸呈正相关，这表明富磷核心随着颗粒的生长而成熟。添加 Ca 增加了直径大于 0.4 毫米的颗粒中总磷含量，但对小于 0.4 毫米的颗粒则没有影响。此外，在 Ca（PO）结晶过程中从水溶液磷酸盐物种释放的 H 通过内部氢营养型产甲烷作用和从颗粒中脱除沼气得到缓冲。这些对 CaP 颗粒形成和生长的深入了解对于工艺优化至关重要，能够在单个反应器中同时回收 Ca（PO）和 CH。此外，由于 pH 值的生物增加导致 Ca（PO）结晶的生物诱导对于在实际环境条件下刺激和控制（生物）结晶和（生物）矿化具有重要意义。
