污水处理厂污泥中磷含量较高,对磷进行回收能有效实现磷资源的二次利用。采用磷酸铵镁(MAP)回收法分别对污泥4种热处理产物阴燃灰、掺烧灰、焚烧灰和热解焦的酸浸出液进行磷回收试验,重点分析了各热处理产物在酸浸出-MAP路线下的磷回收性能,包括磷沉淀率、产物中磷和杂质含量,并进一步探究了沉淀产物的环境安全性。结果表明,通过酸浸出-MAP回收法,单位质量沉淀产物磷质量分数达19.82~31.71mg/g,原污泥中磷回收率达49.25%~65.81%。磷回收性能由高到低依次为焚烧灰、热解焦、阴燃灰、掺烧灰。酸浸出-MAP回收产物中含有大量Ca、Fe、Al和Si杂质,且含有一定量Zn、Pb、Cr、Cu、Cd、As和Ni,其中Zn含量远高于其他重金属含量。产物纯度和环境安全性由高到低依次为焚烧灰、掺烧灰、热解焦、阴燃灰。在沉淀产物的环境安全性方面,阴燃灰、焚烧灰和热解焦的酸浸出-MAP回收产物中重金属含量均符合GB/T23349—2009《肥料中砷、镉、铅、汞生态指标》和GB4284—2018《农用污泥污染物控制标准》。掺烧灰的酸浸出-MAP回收产物中Cd质量分数为3.20mg/kg,超过农用污泥污染物控制标准限值3.00mg/kg。

Sewage sludge contains a large amount of phosphorus, and the recovery of phosphorus can realize the secondary utilization ofphosphorus resources. The phosphorus recovery experiments in the acid leaching solution of four kinds of sludge thermal treatment products, including smoldering ash, mixed ash, incineration ash and pyrolysis coke were conducted by the magnesium ammonium phosphate(MAP) recovery method. The phosphorus recovery performance of each thermal treatment product under the acid leaching-MAP recoveryprocess route was analyzed. The phosphorus precipitation rate, the phosphorus and impurities contents in the products were explored. Theenvironmental safety of the precipitated products was further investigated. The results show that the phosphorus content of the precipitateproduct can reach 19.82-31.71 mg/ g, and the phosphorus recovery rate in the original sludge reaches 49.25%-65.81% by the acid leaching-MAP recovery method. The order of the phosphorus recovery performance is incineration ash > pyrolysis coke > smoldering ash >mixed ash. There are a large number of Ca, Fe, Al and Si impurities in the acid leaching MAP recovery product, and a certain amount ofZn, Pb, Cr, Cu, Cd, As and Ni, with Zn content much higher than other heavy metals. The purity and environmental safety of the products follows the order of incineration ash > mixed ash > pyrolysis coke > smoldering ash. In the terms of the environmental safety of theprecipitated products, the heavy metal content of the acid leaching-MAP recovered products of smoldering ash, incineration ash and pyrolysis coke all meet the " Ecological Index of Arsenic, cadmium, lead and mercury in Fertilizers" written in GB/ T 23349—2009 and the" Control Standard of Pollutants in Agricultural Sludge" written in GB 4284—2018. The content of Cd in the recovered product fromthe mixed ash using acid leaching-MAP is 3.20 mg/ kg, which exceeds the limited value of 3.00 mg/ kg for pollutant control of agriculturalsludge.

0 引言

1 污泥热处理产物的磷回收试验

   1.1 MAP回收试验

   1.2 无机矿物组成分析

   1.3 沉淀产物形貌分析

2 污泥热处理产物酸浸出-MAP回收工艺

   2.1 磷回收量与杂质沉淀率

   2.2 沉淀物分析

3 结论