Which solid treatment methods employ a coagulant polymer and pressure?

The use of a coagulant polymer combined with pressure is a crucial factor in solid treatment methods that aim to enhance the dewatering process and improve the removal of solids from wastewater sludges. In the context of the options given, the belt filter and plate method utilizes both a coagulant polymer and pressure to improve the efficiency of solid-liquid separation.

The belt filter press works by feeding sludge into a thickening section followed by a dewatering section where pressure is applied. The addition of a coagulant polymer helps to bind the fine particles together, forming larger aggregates that are more easily separated from the liquid phase. The application of pressure helps compress the material further, resulting in a drier final product.

In contrast, the other methods listed do not involve the use of a coagulant polymer nor do they typically operate under pressure. Anaerobic digestion focuses on microbial digestion processes without the need for such treatment chemicals. Composting relies on aerobic biological processes to break down organic matter and does not employ polymers or pressure in the dewatering phase. Sand drying beds utilize evaporation, gravity, and passive drainage rather than mechanical pressure and do not use coagulants.

Thus, the belt filter and plate method stands out as the only solid treatment method in