Which type of sludge could block a sanitary sewer system if discharged?

• A. Activated sludge
• B. Lime sludge
• C. Sludge from settling tanks
• D. Digested sludge

Answer: (B)

Lime sludge is the type of sludge that could block a sanitary sewer system if discharged. This type of sludge is a byproduct of water treatment processes, especially when lime is added to the water to soften it or adjust pH levels. The calcium compounds present in lime sludge can create a thick, viscous mixture that may not be easily broken down or dissolved in a sewer system. When discharged, it can accumulate and lead to blockages within piping systems, resulting in costly maintenance and potential environmental hazards.

In contrast, activated sludge, sludge from settling tanks, and digested sludge are generally more manageable when it comes to being handled in wastewater systems. Activated sludge is composed of microorganisms that break down organic matter and is typically processed further in wastewater treatment facilities. Settling tank sludge primarily consists of heavier solids that have settled and are often removed periodically; it does not usually lead to blockages as it is managed appropriately. Digested sludge is processed to reduce its volume and odor, making it less harmful when disposed of. These types of sludge have characteristics that allow for better treatment and handling, minimizing the risk of causing blockages in sanitary sewer systems.