污泥稳定化过程中磷的转化规律和生物有效性

Transformation and Bioavailability of Phosphorus in the Process of Sludge Stabilization

剩余活性污泥(简称污泥)作为污水生化处理的主要副产物,富集大量的磷元素,被认为是一种潜在的磷资源回收对象。本文系统地总结了污泥中磷的组成特征、分析表征方法,并综述了污泥不同稳定化过程中磷的转化规律和生物有效性。结果表明:(1)污泥中有机磷和无机磷含量分别占污泥总磷含量的10%~40%和60%~90%,无机磷主要为聚磷酸盐,有机磷主要为单酯有机磷和二酯有机磷;(2)污泥中磷可以采用顺序提取法分级,磷组成的分析表征方法主要有^(31)P NMR、XRD法、XANES法、色谱法、FTIR法、FT-ICR MS法、酶解法等;(3)在污泥水热和热解过程中,聚磷酸盐和有机磷在高温高压条件下从污泥细胞中溶出,随着水热温度升高,有机磷逐渐分解为PO_(4)^(3-),并在金属离子的捕获下生成稳定的难溶性正磷酸盐,而热解则会使得正磷酸盐进一步发生脱水脱氢反应,形成结构更加紧密和稳定的正磷酸盐矿物,在污泥厌氧消化过程中,厌氧微生物一方面会分解污泥细胞使得污泥中磷释放进入上清液,另一方面会将Fe^(3+)还原为Fe^(2+),促进Fe_(3)(PO_(4))_(2)中的PO_(4)^(3-)溶出,而在污泥好氧堆肥过程中,污泥中磷会被微生物吸收利用,并随着微生物繁殖生成微生物源有机磷,腐熟阶段后,微生物进入衰亡期导致有机磷溶出并与金属离子结合;(4)污泥稳定化产物中无机磷的生物有效性由其溶解度和稳定性决定,而有机磷的生物有效性取决于其酶解的难易程度。该研究结果可为污泥中磷的回收与高效利用奠定理论基础。

As the main by-product of sewage biochemical treatment,waste-activated sludge(refferred to as sludge) enriches a large amount of phosphorus elements,and is considered to be a potential phosphorus resource recovery object.This paper systematically summarizes the composition,analysis and characterization methods of phosphorus in sludge,and summarizes the transformation and bioavailability of phosphorus forms in different stabilization processes of sludge.The organic phosphorus and inorganic phosphorus in the waste-activated sludge account for 10%~40% and 60%~90% of the total phosphorus,respectively.The inorganic phosphorus is mainly polyphosphate;the organic phosphorus is mainly orthophosphate monoester and orthophosphate diester.Phosphorus in sludge can be classified by sequential extraction,and the analysis methods of phosphorus composition mainly include ^(31)P NMR,XRD,XANES,chromatography,FTIR,FT-ICR MS,enzymatic hydrolysis,etc.During the hydrothermal and pyrolysis process of sludge,polyphosphates and organic phosphorus are dissolved from the sludge cell structure under high temperature and high pressure conditions.With the increase of hydrothermal temperature,organic phosphorus is gradually decomposed into PO_(4)^(3-),and stable insoluble phosphates are generated under the capture of metal ions.Pyrolysis will further dehydrate and dehydrogenate phosphate to form a more compact and stable phosphate mineral.In the process of anaerobic digestion,on the one hand,anaerobic microorganisms will decompose sludge cells to release phosphorus in the sludge into the supernatant.On the other hand,they will reduce Fe^(3+) to Fe^(2+) to promote the dissolution of PO_(4)^(3-) in Fe_(3)(PO_(4))_(2).In the process of aerobic composting,the phosphorus in the sludge will be absorbed and utilized by microorganisms,and along with the reproduction of microorganisms,organic phosphorus of microbial origin will be generated.The bioavailability of inorganic phosphorus in sludge stabilization products is determined by its solubility and stability,while the bioavailability of organic phosphorus depends on the ease of enzymatic hydrolysis.The paper systematically summarizes the transformation and biological availability of phosphorus in the process of sludge stabilization,which can lay a theoretical foundation for the recovery and efficient utilization of phosphorus in sludge.