Which disposal method is not acceptable for sludge?

• A. Incineration
• B. Landfilling
• C. Composting
• D. Dilution or ocean dumping

Answer: (D)

Disposal methods for sludge must reduce risk to public health and the environment and meet regulatory requirements. Incineration and landfilling are traditional, regulated ways to manage sludge, with incineration dramatically reducing volume and destroying organic matter and pathogens when designed properly, and landfilling requiring proper containment and leachate control. Composting is another accepted path when the sludge is properly stabilized and tested, producing a biosolid that can be used as a soil amendment if it meets pathogen reduction and contaminant limits.

Dilution or ocean dumping is not acceptable because dilution does not treat or remove contaminants or pathogens; it simply spreads them and can increase exposure risk. Dumping sludge into the ocean is harmful to marine ecosystems and is prohibited by environmental laws and regulations in many jurisdictions.