基于微生物诱导碳酸盐沉淀的垃圾焚烧飞灰固化/稳定化机理与方法

This research is to utilize the rich source of calcium in municipal solid Waste incinerator (MSWI) fly ash for the waste solidification/stabilization treatment on the base of the microbial-induced carbonate precipitation technique (MICP). It will provide a new cost-effective approach for the harmless treatment of the MSWI fly ash. In this research, the physical and chemical properties of the fly ash will be firstly measured. The dissolution characteristics of calcium, water permeability and pozzolanic activity of the fly ash will be measured when it is mixed with water. Then the leaching behavior of heavy metals and dioxins and the leaching pH value from the fly ash will be measured, and their effects on microbial activity will be investigated. Thereafter, the microbial species suitable for the treatment of fly ash will be selected out, and formulation experiments will be carried out. Column tests will be performed to simulate the MICP bio-chemical reaction process. Time domain reflectometer (TDR), shear-wave-velocity-based bending elements and on-line CT scanner will be used to monitor the dynamic process associated with microbial metabolism behavior, ion transfer and adsorption, and carbonate precipitation. The experimental results will be used to reveal the release, transfer and precipitation mechanism of the inner-source calcium, the function of cementation, covering and filling induced by MICP and the synergistic reaction of calcium carbonate and heavy metal carbonate. The mechanical properties, water permeability and leaching property of the treated fly ash will be measured and assessed under the common and adverse environmental conditions. On the base of the pilot-scale experiments, a cost-effective MICP treatment method involving material formula and operation technology will be developed.

本项目利用垃圾焚烧飞灰富含钙源的特点，通过微生物诱导碳酸盐沉淀作用（MICP）对飞灰进行固化/稳定化处理，为其无害化处置开辟一种新途径。首先测试飞灰的物理化学特性，研究飞灰与水作用时钙的溶出特性、渗透性及火山灰活性；测试重金属、二噁英等主要污染物的浸出毒性和酸碱环境，及其对微生物活性的影响。然后优选微生物种类，开展基于MICP的飞灰固化/稳定化配方试验和模拟柱试验。利用电磁波时域反射TDR仪、压电陶瓷弯曲元剪切波速测试仪及在线试验CT机，监测MICP模拟柱中微生物代谢、阳离子传递与吸附、碳酸盐沉淀等动态平衡过程，重点揭示飞灰中内源钙的释放、传递及转化机制、碳酸钙沉淀产生的胶结、包裹、填充作用及其与重金属碳酸盐化的协同作用机理。测试分析飞灰固化体在常规及不利环境下力学性能、渗透特性和主要污染物的浸出毒性。在中试试验基础上，研发一套经济、有效的飞灰MICP处理配方及工艺。

生活垃圾焚烧飞灰属于危险废物，目前国内外还缺乏对飞灰经济、高效的无害化处理技术。本项目利用飞灰富含钙源的特点，通过微生物诱导碳酸盐沉淀作用（MICP）对飞灰进行了固化/稳定化处理，为其无害化处置开辟了一条新途径。首先测试了飞灰的物理化学及环境土工特性；研究了飞灰与水相互作用性质，包括Ca2+有效溶出率、水力渗透特性、水凝硬化性质等性能；测试了飞灰生化环境对脲酶微生物活性的影响；研究了MICP固化飞灰的室内试验方法。然后从种植土壤中优选了几种脲酶微生物，开展了MICP固化/稳定化飞灰的模拟柱试验，监测了剪切波速、pH、电导率和碳酸盐含量的动态变化过程，研究了飞灰固化/稳定化过程中碳酸钙沉淀产生的胶结、包裹、填充作用及其与重金属碳酸盐化的协同作用机理；接着测试分析了飞灰固化体的力学性能、渗透特性和主要污染物的浸出毒性，并进行工程应用的可行性研究。最后提出了一套基于MICP技术的生活垃圾焚烧飞灰固化/稳定化的处理装置和处理工艺。截止到2019年12月，研究课题累计录用发表论文14篇，SCI论文4篇，EI期刊论文2篇，EI会议论文2篇，授权国家发明专利3项，实用新型专利1项。