疏浚泥浆的混凝沉降特性及絮体形态

疏浚工程中会产生大量的疏浚泥浆,其浓度低、颗粒细小、长期悬浮难以沉降,占用大量土地。利用聚丙烯酰胺(PAM)为混凝剂加速泥浆泥水分离,通过沉降界面高度、沉降速率及沉降后上覆水的浊度,确定混凝剂的最佳投加量,利用激光粒度仪和显微镜对絮体粒径及絮体形态进行分析,探究疏浚泥浆的混凝沉降特性及混凝机制,并提出混凝沉降模式。结果表明,在PAM作用下,疏浚泥浆在高混合强度、短时间内即形成较大、较密实的絮体,5 min内基本处于沉降稳定状态;PAM最佳投加量与泥浆含固量有关,为0.8wt%,此时沉降高度最高、沉降速度最快、上覆水浊度最低、絮体粒径基本保持不变、絮体分形维数为最大值。疏浚泥浆的混凝沉降过程经历快速沉降、缓慢沉降、稳定三个阶段,即絮团的沉降、压缩、自重固结过程。

Study on Coagulation-Sedimentation Characteristics and Flocculation Morphology of Dredged Mud

Large amount of dredged mud will be produced in the dredging projects, with a low concentration and fine particles, which were hard to settle. In this paper, polyacrylamide(PAM) is used to accelerate the sedimentation.The optimal dosage of coagulant is determined by the height and rate of the settlement interface, and the turbidity of the overlying water after the settlement. The particle size and shape of the flocculation were analyzed by laser particle size analyzer and microscope. The flocculation sedimentation characteristics and coagulation mechanism of dredged mud were studied. The research show that under the action of PAM, dredging mud forms a large and dense flocculation in a high mixing strength and a short time, and is basically in a stable state of settlement within 5 min. The optimal dosage of PAM is related to the solid content of the mud.It is 0.8 wt %, at which time the sedimentation height is the highest, the sedimentation velocity is the fastest, the overlying water turbidity is the lowest, the floc particle size remains basically unchanged, and the floc fractal dimension is the maximum.The coagulation- sedimentation process of dredged mud goes through three stages: fast settlement, slow settlement and stability, namely, the deposition, compression and self-consolidation of the flocculation.