If you pump green sludge to a drying bed, what chemical should be applied?

When green sludge is pumped to a drying bed, the application of lime is important for several reasons. Lime, or calcium hydroxide, serves multiple functions in the treatment of sludge. It helps to raise the pH of the sludge, which can facilitate the stabilization of organic material and enhance the dewatering process. The increased pH also aids in pathogen reduction, making the final product safer for disposal or potential reuse.

Additionally, when lime reacts with water present in the sludge, it generates heat through an exothermic reaction, which can further assist in evaporation during the drying process. The use of lime improves the overall characteristics of the sludge, making it more suitable for subsequent handling and disposal.

Other options, while relevant in different contexts, do not have the same direct benefits for the drying process of green sludge. For instance, polymers are typically used to aid in flocculation or coagulation, while chlorine is used for disinfection, and alum is primarily used in water treatment for coagulation. Thus, lime is the appropriate choice for enhancing the condition and safety of sludge in a drying bed scenario.