Which type of sludge cannot be discharged to a sanitary sewer system because it might block sewers?

Lime sludge is produced during the water treatment process when lime is added to water to adjust pH levels and precipitate impurities. This type of sludge contains a high concentration of calcium and can have a thick, paste-like consistency that can readily solidify or aggregate. Discharging lime sludge into a sanitary sewer system poses a significant risk of blocking the sewers due to its potential to create solid masses that can accumulate and obstruct flow.

The characteristics of lime sludge—specifically, its ability to harden and its thick consistency—make it unsuitable for disposal in a sewer system where such blockages could create serious problems in the wastewater infrastructure. Proper disposal methods typically involve specialized treatment or disposal separate from the sanitary sewer system.

In contrast, other types of sludge, such as organic sludge, activated sludge, and raw sewage sludge, are generally more fluid and contain a higher percentage of water, making them less likely to cause blockages in sewage systems. Each of these other sludges is typically processed through treatment facilities designed to handle their characteristics without posing the same risks as lime sludge.