Which process is typically used to enhance sludge settleability?

Coagulation is the process that is typically used to enhance sludge settleability in wastewater treatment. This process involves the chemical addition of coagulants, such as aluminum sulfate or ferric chloride, which destabilizes the colloidal particles in the sludge. When these coagulants are added and mixed into the sludge, they cause the smaller particles to agglomerate into larger flocs. These larger flocs have improved settling characteristics because they have a greater mass and are less likely to remain suspended in the liquid.

As the flocs aggregate, their size increases, allowing gravity to pull them to the bottom of the treatment tank more effectively during the settling phase. This enhances the overall efficiency of the sedimentation process, enabling faster and more complete separation of solids from the liquid phase. Improved settleability is crucial as it facilitates the removal of solids from the effluent, thereby ensuring better water quality and compliance with treatment standards.

In contrast, aeration treatment primarily focuses on promoting the biological breakdown of organic matter by supplying oxygen to microorganisms, rather than directly improving sludge settleability. Filtration is a physical separation process typically used for clarifying liquids but does not improve settleability; instead, it acts on already settled solids. Reverse osmosis is a membrane filtration process