石英砂提高氧化亚铁硫杆菌介导的生物沥浸污泥脱水性能的机制研究

Bioleaching is a new technique that improves sludge dewaterability through the effects of Acidithiobacillus bacteria on the biological oxidation, acid production, and other processes involving S0 or Fe2+. During bioleaching, the oxidation product Fe3+ is hydrolyzed to synthesize secondary iron minerals such as schwertmannite and jarosite, and release H+. Increasing the degree of Fe3+ hydrolysis and mineralization not only accelerates the acidification of sludge, but also reduces the sludge compression coefficient to improve sludge dewaterability. In a previous study, we investigated the effects of quartz sand on sludge dewaterability in the bioleaching process mediated by Acidithiobacillus ferrooxidans. We found that quartz sand could significantly improve the dewaterability of sludge and transform the hydrolysis and mineralization product of Fe3+ from schwertmannite to jarosite. We concluded that quartz sand could crack and alter the physical and chemical properties of sludge such as bound water, K+, and NH4+ concentrations, thereby affecting the sludge dewaterability and Fe3+ biomineralization pathway. Based on these previous findings, this study aims to further analyze the characteristics of quartz sand and its application in cracking the sludge system, including the mechanisms by which quartz sand influences the physical properties, chemical properties, and dewaterability of sludge. We also explore the mechanisms by which quartz sand induces change in the synthesis pathway of secondary iron minerals in the bioleaching system and improves sludge dewaterability in bioleaching. The results of this present study provide a scientific basis and technical support for the improvement and regulation of conventional bioleaching technologies for municipal sludge.

生物沥浸法是利用硫杆菌对S0或Fe2+的生物氧化和产酸效应等作用来提高污泥脱水性能的新技术。其中，氧化产物Fe3+会水解合成施氏矿物、黄铁矾等次生铁矿物并释放出H+。提高Fe3+水解矿化程度不仅可加速污泥酸化，亦可降低污泥压缩系数而进一步改善污泥脱水性能。项目申请人曾考察过石英砂对氧化亚铁硫杆菌介导的生物沥浸污泥脱水性能的影响。结果表明，石英砂能够显著改善污泥脱水性能并促使Fe3+水解矿化产物由施氏矿物向黄铁矾转变，推断石英砂会破解改变污泥理化性质（如结合水、K+、NH4+等释放）而影响污泥脱水性能及Fe3+生物矿化途径。在预实验基础上，本项目拟进一步分析石英砂破解污泥体系特点及其影响污泥理化性质和脱水性能的机理；探究石英砂诱导生物沥浸体系次生铁矿物合成途径发生转变的影响机制；揭示石英砂改善生物沥浸污泥脱水性能的作用机制。依此为城市污泥常规生物沥浸技术的改进和调控提供科学依据和技术支撑。

前期研究发现，在A. ferrooxidans介导的污泥生物沥浸体系中引入石英砂后，其对污泥脱水性能的改善较为显著，具体表现为生物沥浸时间缩短，污泥比阻（SRF）进一步降低。深入分析发现，相较于传统生物沥浸，石英砂参与使得生物沥浸体系产生更多的H+；此外，石英砂诱导作用加速了生物沥浸初期Fe3+沉淀速率，并提高体系中的总Fe累积沉淀率（以次生矿物形式沉淀）。然而，石英砂提高生物沥浸污泥脱水性能的主导因素尚不清楚：（1）石英砂促使 Fe3+水解矿化向黄铁矾类矿物转变的原因何在，若石英砂会破解污泥而释放出K+、NH4 +等来改变污泥液相组分，则该如何调控矿物的合成途径以获取更多矿物量。（2）石英砂在诱导矿物合成会释放更多的H+，是否是矿物大量合成而降低污泥压缩系数，或是A. ferrooxidans的生物酸化效应，亦或是二者的综合效应改善了污泥脱水性能。本项目对上述问题做了相关研究，主要方法和结论概括如下：（1）考察了有或无石英砂（40g/L）时生物矿化过程中各指标变化情况。结果表明，石英砂有助于Fe2+氧化产物Fe3+的水解矿化从而提高总Fe去除率。添加石英砂前后，K+、NH4+、Na+体系培养终点pH分别从2.17、2.31和2.32下降至1.86、2.04和1.96；溶液总Fe去除率分别从31.5%、9.5%和12.1%上升至58.1%、22.2%和42.3%。XRD图谱表明，石英砂还能促使Fe3+生物矿化途径由施氏矿物向黄铁矾转变。（2）通过摇瓶实验探究石英砂提高城市污泥生物沥浸效率的主导因素。结果表明，在0~72h内，生物菌液酸化效应在提高污泥脱水性能中占据主导作用；在72h之后，次生矿物的形成对提高污泥脱水性能的贡献率超过生物菌液。随着生物沥浸持续进行，石英砂诱导次生矿物产量逐渐增加，次生矿物在生物菌液酸化效应基础上进一步强化污泥脱水性能。在二者耦合作用下，SRF从初始的17.13×1012m/kg下降至48h时的最低值3.56×1012m/kg。然而，生物菌液和次生矿物单独作用时，SRF降到最低值均需72h，且最低SRF分别为3.89×1012和4.77×1012m/kg。可见，二者耦合作用在进一步改善污泥脱水性能及缩短生物沥浸时间方面都有明显的优势。