Abstract:

The migration and transformation of phosphorus in sewage sludge and its derived hydrochar during the hydrothermal carbonization (HTC) process has been investigated using standards, measurements, and testing (SMT) protocol, combining with X-ray diffraction (XRD) technique. The results showed that the organic phosphorus (OP) in the dried sewage sludge almost transformed to inorganic phosphorus (IP) following HTC treatment. Within the experimental conditions, the phosphorus was concentrated in the hydrochar in terms of its recovery rate R_TP＞70% and presented as IP after HTC. Both extending the HTC duration and increasing the HTC temperature could make the contents of IP and non-apatite inorganic phosphorus (NAIP) rise gradually. Furthermore, the HTC temperature had greater influence on their contents than the HTC duration did. The HTC duration had little effect on the content of apatite phosphorus (AP) while the impact of HTC temperature on AP content was significant. XRD patterns showed that the sewage sludge dried at 105℃ mainly contained aluminum phosphate and ferric phosphate. During the HTC process, pyrophosphate could convert to orthophosphate. The phosphorus in the hydrochar was mainly in the most stable forms of orthophosphate after HTC treatment. The results described here can provide new insights into the phosphorus recovery from sewage sludge.

Key words: sewage sludge, hydrothermal carbonization, phosphorus, migration and transformation, waste treatment

摘要：

利用SMT方法研究了污水污泥水热炭化固体产物中磷的赋存形态和分布。结果表明，水热炭化处理可以使污泥中的有机磷（OP）转化为无机磷（IP）。在实验条件范围内，污泥中的磷主要富集在水热焦中（R_TP＞70%），且主要以无机磷（IP）形态存在。延长水热炭化时间或升高水热炭化温度，污泥中无机磷（IP）和非磷灰石无机磷（NAIP）均呈逐渐升高的趋势，而且水热炭化温度的影响程度显著大于水热炭化时间。水热炭化时间对磷灰石无机磷（AP）的影响不明显，但AP含量随水热炭化温度的升高而略微升高。结合XRD谱图分析发现，105℃烘干污泥中主要存在磷酸铝盐和磷酸铁盐两种含磷化合物；水热炭化处理促使焦磷酸盐转化为正磷酸盐，且磷在水热焦中基本以最稳定的正磷酸盐形式存在。该研究结果可为污泥的资源化利用及从污泥中回收磷资源提供理论参考。

关键词: 污水污泥, 水热炭化, 磷, 迁移转化, 废物处理