Metabolon Institute, TH Köln (University of Applied Sciences), Am Berkebach 1, 51789 Lindlar, Germany.
Metabolon Institute, TH Köln (University of Applied Sciences), Am Berkebach 1, 51789 Lindlar, Germany.
Waste Manag. 2023 Jun 15;165:150-158. doi: 10.1016/j.wasman.2023.04.010. Epub 2023 Apr 29.
Phosphorus (P) is a non-regenerative and finite raw material. Due to its decreasing availability, and to protect the environment, recycling methods are needed. With the focus on closing nutrient cycles, sewage sludge (SS) is a potential source for P recovery. The objective of this study was to produce a mineral P-reach fertilizer. For this purpose, the treatment of SS in a multi-stage process, consisting of a hydrothermal carbonization (HTC) and thermochemical post-treatment was examined and compared with a direct thermochemical treatment. The focus was on the transformation of P and the migration of the heavy metals during the processes. In addition, the role of MgCl as an additive was examined. During the HTC, most of the P remained in the HTC-char, so that the P content increased in the HTC-char compared with the SS. The addition of MgCl to the process resulted in lower transportation rates of P in the liquid phase and higher P solubilities in water, citric acid, and alkalic ammonium citrate out of the solid phase. The thermochemical treatment of SS and the HTC-chars further concentrated P in the ash. Retention rates of >97% were achieved, and PO contents in the ash were as high as ∼16 wt-%. The presence of the additive resulted in (i) higher retention rates of P in the ashes (ii) higher P-solubility and (iii) higher removal rates of easily volatile heavy metals such as Pb and Zn, and the treatment of HTC-char favored these effects compared with the direct treatment of SS.
磷（P）是一种不可再生且有限的原材料。由于其供应量不断减少，为了保护环境，需要采用回收方法。鉴于要重点闭合营养循环，污水污泥（SS）是回收磷的潜在来源。本研究的目的是生产一种矿物 P 肥。为此，研究了多阶段工艺（包括水热碳化（HTC）和热化学后处理）处理 SS，并与直接热化学处理进行了比较。重点是研究过程中 P 的转化和重金属的迁移。此外，还研究了 MgCl 作为添加剂的作用。在 HTC 过程中，大部分 P 仍留在 HTC 炭中，因此与 SS 相比，HTC 炭中的 P 含量增加。向该工艺中添加 MgCl 会导致液相中 P 的传输率降低，并且水、柠檬酸和碱性柠檬酸铵中的固相 P 溶解度增加。SS 和 HTC 炭的热化学处理进一步将 P 浓缩在灰分中。回收率>97%，灰分中的 PO 含量高达约 16wt-%。添加剂的存在导致（i）灰分中 P 的保留率更高（ii）P 溶解度更高（iii）易挥发重金属如 Pb 和 Zn 的去除率更高，与直接处理 SS 相比，HTC 炭的处理有利于这些效果。
