Which chemical is often used to aid in sludge dewatering processes?

Alum, or aluminum sulfate, is commonly used in sludge dewatering processes because it acts as a coagulant. When added to wastewater, alum helps to aggregate smaller particles into larger flocs, which can then be more easily removed from the liquid phase. This aggregation is essential in the dewatering process because it improves the efficiency of separating water from the sludge, leading to reduced moisture content in the final product and facilitating handling and disposal.

The effectiveness of alum is particularly evident in its ability to reduce the volume of sludge and enhance solid-liquid separation, which are critical factors in wastewater treatment. This is why it is a preferred choice among operators dealing with sludge management.

In contrast, hydrochloric acid is primarily a strong acid used for pH adjustment and is not used for dewatering. Calcium carbonate serves mainly as a pH buffer and does not function efficiently in the same capacity as a dewatering agent. Sodium chloride, though involved in various chemical processes, does not contribute effectively to the sludge dewatering process.