低基质CANDAN-HAP颗粒表层矿化与结构响应

Surface Mineralization and Structural Response of Granular Sludge in a Low-Substrate CANDAN-HAP System

摘要: 为揭示低基质条件下CANDAN-HAP颗粒污泥在矿化增强过程中的结构演化特征及其潜在影响，文章以不同运行阶段颗粒污泥为对象，采用VSS/SS测定、体式显微镜、扫描电子显微镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)等方法，对颗粒宏观外观、微观晶体形貌、元素分布及矿物相变化进行分析。结果表明，在92 d运行过程中，体系脱氮功能总体保持稳定，磷去除随pH由7.5提高至8.1。随着矿化增强，颗粒污泥VSS/SS由76.3%降至52.0%和33.8%；SVI降低，表明无机组分累积促进了颗粒致密化和沉降性能改善。颗粒表面由相对均一的生物性外观逐渐转变为白化、粗糙化并伴有结节状沉积的复合外观；SEM-EDS结果显示，颗粒表层由致密微生物聚集结构逐步发展为Ca-P富集沉积，并在后期形成大面积板状晶体堆积。XRD半定量分析表明，阶段三31˚~33˚ HAP主特征峰区积分面积较阶段二提高约8.7%，说明HAP相关晶相的相对衍射信号增强。总体来看，低基质CANDAN-HAP颗粒表层矿化经历了由弱沉积、局部富集到晶体成熟的阶段性演化路径；适度矿化有利于颗粒致密化和磷固定，但后期表层晶体堆积可能增强结构异质性，并带来潜在传质和脆化风险。

Abstract: To reveal the structural evolution characteristics and potential impacts of CANDAN-HAP particle sludge during the mineralization enhancement process under low substrate conditions, using different operational stages of the particle sludge as the objects, methods such as VSS/SS determination, body-type microscopes, scanning electron microscopes (SEM), energy-dispersive X-ray analysis (EDS), and X-ray diffraction (XRD) were employed to analyze the macroscopic appearance, microscopic crystal morphology, element distribution, and mineral phase changes of the particles. The results showed that during the 92-day operation, the nitrogen removal function of the system remained stable overall, and phosphorus removal increased as pH increased from 7.5 to 8.1. With mineralization enhancement, the VSS/SS of the particle sludge decreased from 76.3% to 52.0% and 33.8%, and SVI decreased, indicating that the accumulation of inorganic components promoted the densification of the particles and the improvement of their sedimentation performance. The particle surface gradually changed from a relatively uniform biological appearance to a bleached, roughened, and nodular deposition composite appearance. The SEM-EDS results showed that the surface of the particles gradually developed from a dense microbial aggregation structure to Ca-P-enriched deposition, and in the later stage, large-area plate-like crystal accumulations were formed. XRD semi-quantitative analysis indicated that the integrated area of the main HAP characteristic peak region at 31˚~33˚ in Stage III increased by approximately 8.7% compared with Stage II, suggesting enhanced relative diffraction signals of HAP-related crystalline phases. Overall, the surface mineralization of low-substrate CANDAN-HAP particles underwent a phased evolution path from weak deposition, local enrichment to crystal maturity; moderate mineralization was beneficial for particle densification and phosphorus fixation, but the later accumulation of surface crystals might enhance structural heterogeneity and bring potential mass transfer and brittle failure risks.