In this study, the influence of Na₂SO₄ on electro-dewatering (EDW) of waste activated sludge (WAS) was investigated. The highest water removal efficiency of 42.5% was achieved at the optimum Na₂SO₄ dosage of 12.5 g kg⁻¹ DS during EDW process at a constant voltage of 20 V. The migration and distribution of water, organic matters and Na⁺ at different Na₂SO₄ dosages were investigated through layered experiments. The results indicated the entire EDW process followed the S curve model, and it can be divided into three stages: (1) initial desalination stage: at the initial few min of EDW process, the rate of electroosmosis was extremely slow while electromigration of ions like Na⁺ was intense, and the electromigration was more obvious with increased Na₂SO₄ dosage; (2) dewatering stage: the dewatering efficiency increased dramatically via electroosmosis; (3) the dewaterability limit stage: the maximum value of dewatering efficiency has been achieved, while the water removal efficiency and dry solids content remained constant. During the EDW process, the possible electrolysis resulted in a pH gradient in the sludge cake. With the addition of Na₂SO₄ in the EDW, the pH gradient was intensified, and the migration rate of organic matters moving from cathode to anode increased while compared with the raw WAS. This study provided insights into the mechanism of EDW process at different dosages of Na₂SO₄.

中文翻译：

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不同剂量硫酸钠对废活性污泥电脱水过程中钠离子和有机物的迁移和分布

在这项研究中，研究了Na ₂ SO ₄对废活性污泥（WAS）的电脱水（EDW）的影响。在EDW过程中，在20 V恒定电压下，最佳Na ₂ SO ₄剂量为12.5 g kg ^-1 DS时，最高除水效率达到42.5％。水，有机物和Na ⁺在不同电压下的迁移和分布Na ₂ SO ₄通过分层实验研究剂量。结果表明，整个EDW过程遵循S曲线模型，可分为三个阶段：（1）初始脱盐阶段：在EDW过程的最初几分钟，电渗速率极慢，而离子之类的离子电迁移Na ⁺强烈，并且随着Na ₂ SO _4的增加，电迁移更加明显剂量; （2）脱水阶段：电渗法使脱水效率大大提高。（3）脱水极限阶段：脱水效率达到最大值，除水率和干固含量保持恒定。在EDW过程中，可能的电解导致了污泥饼中的pH梯度。与原始WAS相比，在EDW中添加Na ₂ SO _4可以增强pH梯度，并且有机物从阴极迁移到阳极的迁移速率增加。这项研究为不同剂量的Na ₂ SO ₄对EDW过程的机理提供了见解。