Xu Haiqing, Guo Liang, Gao Mengchun, Zhao Yangguo, Jin Chunji, Ji Junyuan, She Zonglian
The Key Laboratory of Water and Sediment Sciences, Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, China; State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environmental and Ecology, Ministry of Education, Ocean University of China, Qingdao 266100, China.
Sci Total Environ. 2022 Jun 15;825:154110. doi: 10.1016/j.scitotenv.2022.154110. Epub 2022 Feb 23.
Phosphorus recovery from waste activated sludge (WAS) is expected to alleviate the shortage of phosphate rock and reduce eutrophication. In this study, acid, alkali and sodium polyacrylate (PAAS) were compared to enhance phosphorus release and recovery from WAS. During anaerobic fermentation (AF) stage, the optimal pretreated conditions for ortho-phosphate release were the pH of 4 (AF 12 h), 13 (AF 12 h) and 22.4 g PAAS/L (AF 24 h) with the phosphorus release efficiencies of 40.9%, 62.6% and 31.7%, respectively. Acid, alkali and PAAS addition were beneficial for apatite phosphorus (AP), non-apatite inorganic phosphorus (NAIP) and organic phosphorus (OP) release from WAS, respectively. Strong acidic (pH = 4) and alkaline (pH = 12 and 13) conditions inhibited the release of soluble ammonia, while PAAS would not have a negative impact on the release of soluble ammonia. By means of precipitation crystallization, the ortho-phosphate could be almost recovered after acid/alkali pretreatment compared with PAAS (88.9%) at optimal Mg/P molar ratio of 1.5:1. The XRD, FT-IR and SEM-EDX analyses confirmed the main component in the product was struvite. The purity of the struvite in the product recovered from acid (named Pre, 78.9%) and alkali (named Pre, 89.6%) pretreated sludge were higher than that of the PAAS (named Pre, 72.3%) by elemental analysis. The mercury and chromium content existed in Pre were above the Control Standards of Pollutants in Sludge for Agricultural Use, whereas detected heavy metal elements level of the Pre and Pre were below the standard. By means of cost analysis, acid/alkali pretreatment could obtain economic benefits compared with PAAS. Thus, those discoveries would broaden the phosphorus recovery way to serve in practice.
从剩余活性污泥（WAS）中回收磷有望缓解磷矿石短缺问题并减少富营养化。在本研究中，对酸、碱和聚丙烯酸钠（PAAS）进行了比较，以提高从WAS中释放和回收磷的效率。在厌氧发酵（AF）阶段，正磷酸盐释放的最佳预处理条件分别为pH值4（AF 12小时）、13（AF 12小时）和22.4 g PAAS/L（AF 24小时），磷释放效率分别为40.9%、62.6%和31.7%。添加酸、碱和PAAS分别有利于从WAS中释放磷灰石磷（AP）、非磷灰石无机磷（NAIP）和有机磷（OP）。强酸性（pH = 4）和碱性（pH = 12和13）条件抑制了可溶性氨的释放，而PAAS对可溶性氨的释放没有负面影响。通过沉淀结晶，在最佳Mg/P摩尔比为1.5:1时，与PAAS（88.9%）相比，酸/碱预处理后正磷酸盐几乎可以完全回收。XRD、FT-IR和SEM-EDX分析证实产物中的主要成分是鸟粪石。通过元素分析，从酸（命名为Pre，78.9%）和碱（命名为Pre，89.6%）预处理污泥中回收的产物中鸟粪石的纯度高于PAAS（命名为Pre，72.3%）。Pre中汞和铬的含量高于《农用污泥污染物控制标准》，而Pre和Pre中检测到的重金属元素水平低于标准。通过成本分析，与PAAS相比，酸/碱预处理可以获得经济效益。因此，这些发现将拓宽磷回收途径，以便在实际中应用。
