高铁酸钾预氧化联用改性木质素混凝工艺的污泥脱水性能研究

Potassium ferrate preoxidation coupled with modified lignin coagulation process for sludge dewatering study

污水处理过程中产生大量亟需减量化处理的活性污泥,而污泥中胞外聚合物(EPS)是影响污泥脱水性能的关键因素.传统混凝预处理工艺难以有效地破坏EPS,释放结合水.本研究以南京市仙林某市政污水处理厂活性污泥为研究对象,先采用高铁酸钾(K_(2)FeO_(4))对污泥进行预氧化,再以一种阳离子改性木质素(LN-CD)为混凝剂对污泥进行混凝处理.系统考察了K_(2)FeO_(4)预氧化联用LN-CD混凝工艺对活性污泥的调理性能及其协同污泥脱水机制.研究结果表明,K_(2)FeO_(4)预氧化联用LN-CD混凝工艺具有良好的污泥调理效果,氧化剂投加量和混凝剂电荷密度(CD)是影响脱水性能的重要因素.经适量K_(2)FeO_(4)预氧化并联用CD最高的LN-CD1混凝处理,混凝剂用量最少而脱水效果最佳,且获得的污泥絮体尺寸最大结构也最为紧密.EPS不同形态中蛋白质(PN)二级结构分析结果表明,经预氧化-混凝工艺处理后PN结构从有序紧密转变为松散结构,有利于进一步脱水.这是由于经K_(2)FeO_(4)氧化作用,EPS结构被破坏,EPS中结合水得以释放,并且K_(2)FeO_(4)氧化后生成的三价铁还可起到一定协同混凝作用;而LN-CD通过电中和及黏结架桥作用有效抑制EPS,进一步聚集污泥颗粒实现有效脱水;此外,LN-CD还可利用其刚性结构特征起到骨料支撑作用,有利于改善泥饼可压缩性,协同促进污泥脱水.综上,K_(2)FeO_(4)预氧化联用LN-CD混凝工艺在污泥脱水工艺中具有良好的应用前景.

The treatment of sewage generates a significant volume of activated sludge,requiring efficient volume reduction methods.Extracellular polymeric substance(EPS)in the sludge plays a crucial role in affecting dewatering performance.Traditional coagulation pretreatment struggles to effectively destroy EPS and release bound water.In this study,activated sludge from a municipal sewage treatment plant in Xianlin,Nanjing,was preoxidized with potassium ferrate(K_(2)FeO_(4)),and then a cationically modified lignin(LN-CD)as a coagulant to condition the oxidized sludge.We systematically investigated the dewatering performance and the synergistic mechanisms of combining K_(2)FeO_(4) preoxidation and LN-CD coagulation.Our findings show that K_(2)FeO_(4) preoxidation,combined with LN-CD coagulation,significantly enhances the sludge conditioning effect.The dose of the oxidizer and the charge density(CD)of the coagulant are important factors affecting the dewatering performance.Employing an optical dose of K_(2)FeO_(4) preoxidation followed by LN-CD1 coagulation,which has the highest CD in this series of LN-CDs,minimized the need for coagulant while maximizing dewatering efficiency.This treatment resulted in the formation of the largest,most compact sludge flocks.Analysis of the secondary structure of proteins(PNs)in different forms of EPS revealed a transition from an ordered,compact arrangement to a looser structure following the combined preoxidation and coagulation process,which was conducive to deep dewatering.This effect is attributed to the disruption of EPS structure by K_(2)FeO_(4) oxidation,releasing bound water and allowing the trivalent iron generated after the oxidation.LN-CD supports sludge particle aggregation through charge neutralization and bridging flocculation effects.Its rigid structure also serves as a skeleton builder,improving sludge cake and promoting compressibility and dewatering performance.In summary,K_(2)FeO_(4) preoxidation combined with the LN-CD coagulation process should have a good application prospect in the sludge dewatering process.