冷冻温度对冻融污泥有机物变化的影响

Effect of freezing temperature on freeze／thaw sludge organic matter transformation

摘要:

为了明确冷冻温度对冻融处理剩余污泥时有机物变化的影响,寻求最佳的冻融处理方式,考查了-20、-10以及-5 ℃条件下冷冻,再于20 ℃融化后污泥中有机物质量浓度的变化,并通过红外光谱分析冻融污泥中有机物组分的变化．结果表明,冻融后的污泥内固体物质溶出主要发生在未完全冷冻阶段,延长冷冻时间,固体破解程度趋于稳定．完全冷冻即进入固化阶段(-20 ℃时2.5 h; -10 ℃时3～4 h; -5 ℃时4～6 h)的污泥,污泥絮体网状结构被破坏;融化后,污泥胞内有机物大量溶出．在-5／20 ℃条件下冻／融,污泥上清液中亲水性有机物(hydrophilic fraction, HPI)组分所占比例增加到59.3％,并可较彻底地破解污泥胞外有机物(extracellular biological organic matter, EBOM)疏水性组分中的蛋白质,同时烃类及糖类化合物吸收峰在处理后显著增加．相对-20／20 ℃条件下冻／融,-5／20 ℃下冻／融可以更好地释放污泥胞内有机物并改善污泥的可生化性．为了获得更好的冻融效果,可在-5 ℃的条件下进行冷冻,当污泥完全冷冻后(即冷冻4～6 h)再将污泥转入相对较低的冷冻温度条件下进行后续的固化,最后在室温条件下融化．

Abstract:

To research the effect of freezing temperature on organic matter transformation during freeze／thaw treatment of excess sludge, and to seek the best way of freeze／thaw process, the organic matter transformation during excess sludge disintegration, frozen at -20, -10 and -5 ℃ and thawed at room temperature (20 ℃), respectively, were investigated. The characteristics of organic matter changes of freeze／thaw sludge were also examined using infrared spectrum analysis. The results indicated that the dissolution of solid matter in sludge mainly occurred in the freezing stage, reaching stable after prolonged freezing time. The floc matrix structure was disrupted for the completely frozen sludge (-20 ℃, after 2.5 h; -10 ℃, after 3-4 h and -5 ℃, after 4-6 h), and organic matter sharply released after thawing for 12 h. Under the condition of -5／20 ℃ (freeze／thaw) treatment, the proportion of hydrophilic fraction (HPI) component was increased to 59.3％ and the proteins of hydrophobic components in extracellular biological organic matter (EBOM) were disintegrated thoroughly. In addition, hydrocarbon and carbohydrate absorption peak were increased under -5 ℃ freezing. Compared with the -20／20 ℃ (freeze／thaw) treatment, the intracellular organic matter could be released more thoroughly and the sludge biodegradability was improved via -5／20 ℃ (freeze／thaw) treatment. To obtain the better performance of freeze／thaw treatment, sludge could be firstly frozen at -5 ℃. When sludge was frozen completely (frozen 4-6 h), it could be transferred into the lower freezing temperature for subsequent curing and finally thawed at room temperature.