What is the primary purpose of adding polymer in sludge treatment?

The primary purpose of adding polymer in sludge treatment is dewatering. Polymers act as flocculants, which means they help to bind the solid particles in the sludge together, forming larger aggregates or "flocs." This process improves the efficiency of water removal during the dewatering phase.

When sludge is treated with polymers, the larger flocs can be more easily separated from the liquid phase, reducing the moisture content of the sludge. This is crucial because decreased water content improves the handling and disposal of the sludge by lowering its volume and weight, making transportation and storage more efficient. Dewatering is an essential step in wastewater treatment that ultimately leads to a more manageable and concentrated sludge that can be more easily treated or disposed of.

While reducing volume is a beneficial outcome of dewatering, the specific function of the polymer in this context is to facilitate the dewatering process itself. Increasing pH does not directly relate to the role of polymer in sludge, nor does increasing biochemical oxygen demand (BOD), as these factors pertain to different aspects of wastewater treatment.