来自水资源回收设施(WRRF)的A类生物固体越来越多地用作合成肥料的可持续替代品。然而,生物固体中的高磷氮比导致反复土地施用后磷的潜在积累。提取vivianite,FeP矿物,在生物固体处理的最终脱水步骤之前,可以降低所得A类生物固体中的P含量,并实现更接近合成肥料的1:2的P:N比。使用ICP-MS,IC,紫外可见比色法,穆斯堡尔谱学,和SEM-EDX,在整个生物固体处理系统中,对BluePlains高级废水处理厂(AWTTP)的Vivianite进行了全面表征。结果表明,在初级污泥浓缩中,钙铁矿结合的磷,在预脱水之前,热水解后,厌氧消化后相当于8%,52%,40%,和处理进水总磷的49%。同样,与vivianite结合的铁浓度也对应于8%,52%,40%,和存在的总铁的49%(来自FeCl3剂量),因为总铁和总进磷之间的总摩尔比为1.5:1,这是相同的vivianite化学计量。根据蓝色平原A类生物固体中当前的P:N水平,在具有高Vivianite含量的位置中需要40%至理想地70%的Vivianite回收目标,以在所得A类生物固体中达到与合成肥料分别匹配的1:1.3至1:2的P:N比。对从回收的vivianite中回收铁的财务分析估计,BluePlain的年度FeCl3需求的14-25%可能得到满足。此外,使用VisualMinteq进行的模型模拟用于评估在不同固体处理列车位置最大化Vivianite回收率的预处理方案。
Class A biosolids from water resource recovery facilities (WRRFs) are increasingly used as sustainable alternatives to synthetic fertilizers. However, the high phosphorus to nitrogen ratio in biosolids leads to a potential accumulation of phosphorus after repeated land applications. Extracting
vivianite, an FeP mineral, prior to the final dewatering step in the biosolids treatment can reduce the P content in the resulting class A biosolids and achieve a P:N ratio closer to the 1:2 of synthetic fertilizers. Using ICP-MS, IC, UV-Vis colorimetric methods, Mössbauer spectroscopy, and SEM-EDX, a full-scale characterization of vivianite at the Blue Plains Advanced Wastewater Treatment Plant (AWTTP) was surveyed throughout the biosolids treatment train. Results showed that the
vivianite-bound phosphorus in primary sludge thickening, before pre-dewatering, after thermal hydrolysis, and after anaerobic digestion corresponded to 8 %, 52 %, 40 %, and 49 % of the total phosphorus in the treatment influent. Similarly, the
vivianite-bound iron concentration also corresponded to 8 %, 52 %, 40 %, and 49 % of the total iron present (from FeCl3 dosing), because the molar ratio between total iron and total incoming phosphorus was 1.5:1, which is the same stoichiometry of vivianite. Based on current P:N levels in the Class A biosolids at Blue Plains, a
vivianite recovery target of 40 % to ideally 70 % is required in locations with high vivianite content to reach a P:N ratio in the resulting class A biosolid that matches synthetic fertilizers of 1:1.3 to 1:2, respectively. A financial analysis on recycling iron from the recovered
vivianite had estimated that 14-25 % of Blue Plain\'s annual FeCl3 demand can potentially be met. Additionally, model simulations with Visual Minteq were used to evaluate the pre-treatment options that maximize vivianite recovery at different solids treatment train locations.