Florida Wastewater Practice Test

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

1. Lime

2. Sodium Hydroxide

3. Alum

4. Calcium Carbonate

The correct answer is: Lime

When managing green sludge, applying lime is a common practice due to its ability to effectively raise the pH of the sludge. Lime, primarily calcium oxide or calcium hydroxide, acts as a powerful alkaline material that can stabilize the organic content of the sludge. Adding lime not only aids in the reduction of pathogens, making the sludge safer for handling but also improves the dewatering process by facilitating the flocculation of solids. Furthermore, lime helps to immobilize heavy metals that may be present in the sludge and reduces odors, which can be a significant issue during drying and processing. By increasing the sludge’s pH, lime promotes the transformation of harmful compounds into less toxic or more manageable forms, ultimately enhancing the effectiveness of the drying bed process. While other chemicals mentioned in the choices might be used in specific contexts, they do not serve the same broad purposes or benefits that lime does when applied to green sludge in a drying bed scenario.