School of Environmental Science & Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
School of Environmental Science & Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China.
J Environ Manage. 2021 Apr 15;284:112020. doi: 10.1016/j.jenvman.2021.112020. Epub 2021 Jan 25.
Sludge dewatering is necessary to reduce the volume of sludge for cost-effective transport and ultimate disposal. In this study, a novel combined chemical conditioning process was proposed to improve sludge dewatering performance in which sludge flocs were destructed by sodium dichloroisocyanurate (DCCNa) and re-flocculated by Al(SO) and the mechanism was elucidated. The results showed that sludge capillary suction time (CST) dropped to 15.4 s and moisture content of dewatered sludge cake (Mc) deceased to 71.01% respectively, after the application of combined conditioning with the optimal dosage of 200 mg DCCNa/g dry solids (DS) and 80 mg Al(SO)/g DS. With chemical conditioning, sludge physicochemical properties were greatly changed. With the DCCNa application, the percentage of low-molecular-weight substances in soluble extracellular polymeric substances (S-EPS) increased. Also, the sludge zeta potential dropped from -16.85 mV to -25.45 mV and the median particle size (D50) decreased from 54.1 μm to 51.6 μm. However, the subsequent conditioning by Al(SO) dosing not only led to an increment of 18% in the portion of macromolecules in S-EPS, but also increased the zeta potential and D50 to -10.74 mV and 53.2 μm, respectively. The bound water content in sludge declined from 2.92 g/g DS to 1.98 g/g DS after combined conditioning. We concluded that DCCNa disintegrated the sludge flocs and microbial cells leading to the release of bound water, fine particles and organic substances with negative charge, and the fine colloidal particles can be flocculated into large dense aggregations with the dosing of Al(SO). In summary, the proposed combined conditioning provided a highly effective and environmental friendly approach to improve the sludge dewatering performance.
污泥脱水对于降低污泥运输成本和最终处置成本至关重要。在这项研究中，提出了一种新型的组合化学调理工艺，通过使用二氯异氰尿酸钠（DCCNa）破坏污泥絮体，然后用硫酸铝（Al(SO)）重新絮凝，以改善污泥脱水性能，并对其机理进行了阐述。结果表明，当组合调理的最佳投加量为 200mg DCCNa/g 干固体（DS）和 80mg Al(SO)/g DS 时，污泥毛细吸水时间（CST）分别降至 15.4s，脱水污泥饼的含水率（Mc）降至 71.01%。经过化学调理，污泥的理化性质发生了很大变化。随着 DCCNa 的投加，可溶胞外聚合物（S-EPS）中低分子量物质的比例增加。同时，污泥的zeta 电位从-16.85mV 降至-25.45mV，中值粒径（D50）从 54.1μm 降至 51.6μm。然而，随后投加 Al(SO)不仅使 S-EPS 中大分子的比例增加了 18%，而且还增加了 zeta 电位和 D50，分别为-10.74mV 和 53.2μm。经过组合调理后，污泥中的结合水含量从 2.92g/g DS 降至 1.98g/g DS。我们得出结论，DCCNa 破坏了污泥絮体和微生物细胞，导致结合水、细颗粒和带负电荷的有机物质的释放，而细小的胶体颗粒可以与 Al(SO)的投加一起絮凝成大而致密的聚集体。综上所述，所提出的组合调理为改善污泥脱水性能提供了一种高效、环保的方法。
