水热处理对污泥水分分布的影响

Effect of thermal hydrolysis on moisture distribution of sewage sludge

采用低场核磁共振(LF-NMR)技术研究水热处理对污泥水分分布的影响.通过研究水热温度、反应时间、CaCl2与非离子型聚丙烯酰胺(PAM)添加量对污泥离心水的质量分数的影响,确定最佳处理工况.结合泥饼水的质量分数、氨氮(NH3-N)及溶解性化学需氧量(SCOD)分析,评价经水热处理后污泥样品的脱水性能.研究水热单一变量对污泥水分分布变化的影响.结果表明:反应温度的提高使得污泥中结合水和机械结合水均显著降低;反应时间的延长降低了污泥中的结合水比例;投放氯化钙主要降低机械结合水的比例;PAM的添加量对水分分布影响较小.水热正交实验结果表明:在水热温度为230℃、处理时间为45min时,同时添加140mg/g干污泥(DS)CaCl2,在水热处理后添加10-6 g/g DS PAM试剂的工况下,泥饼经离心脱水后水的质量分数由88.67%降至70.68%.与污泥原样相比,悬浮液中的SCOD、NH3-N值大幅上升,说明污泥絮体中不溶的有机组分发生了水解,并改变了污泥的水分分布.

The effect of thermal hydrolysis on moisture distribution of sewage sludge was investigated by using low-field NMR（LF-NMR）. The optimal operating conditions were obtained by setting reaction temperature,reaction time,dosage of CaCl2 and PAM as four impact factors.The water in sludge content of sludge cake,soluted chemical oxygen demand and NH3-N were employed to evaluate the dewaterability of sewage sludge after thermal hydrolysis.Various working conditions were tested to investigate the influence of different parameters on the moisture distribution of sludge.Results show that both mechanical bound water and bound water in sludge decrease significantly with the increase of working temperature.The increase of reaction time helps to decrease the bound water content.The changing dosage of CaCl2 has major influence of mechanical bound water content;the addition of PAM causes small effect on moisture distribution.Results point out that the optimal operating conditions were 230℃,45 min with 140mg/g dry sludge（DS）CaCl2and 10-6 g/g DS PAM.After centrifugation,the water content of sludge cake dramatically decreases from 88.67 % to 70.68 %.Meanwhile,the SCOD and NH3-N in supernatant increase remarkably,indicating that the insoluble organic components from sludge flocs are hydrolyzed and the moisture distribution is changed.