Why should alum sludge from a treatment plant not be used on agricultural land?

Alum sludge, which is a by-product of the water treatment process where aluminum sulfate (alum) is used as a coagulant, is generally not suitable for agricultural land primarily because it can lead to soil hardness. When applied to soil, alum sludge can change the physical structure of the soil, making it compact and reducing its porosity. This not only limits water infiltration but can also impede root growth, negatively affecting plant health and crop yields.

While some might argue that alum sludge increases nutrient levels or attracts pests, the fundamental concern is the improper alteration of soil structure that occurs. The long-term implications of applying alum sludge without proper treatment and understanding of its composition can lead to challenges in soil management and agricultural productivity.