What is considered the most economical sludge disposal method for lime-soda ash softening plants?

• A. Composting
• B. Incineration
• C. Lagoons
• D. Landfilling

Answer: (C)

Lagoons are recognized as the most economical sludge disposal method for lime-soda ash softening plants primarily due to their lower operational and maintenance costs compared to other methods. In lagoon systems, sludge is allowed to settle and decompose naturally over time, which significantly reduces the need for mechanical processing and handling. This method leverages natural biological processes, requires less investment in infrastructure for treatment, and can effectively accommodate varying volumes of sludge without the need for continuous management.

Additionally, lagoons can provide sufficient space for the treatment of the sludge without incurring the higher costs associated with technologies like incineration or landfilling, which often require more restrictive handling practices and regulatory compliance. Composting may be more environmentally friendly but often involves additional processing and time, making it less economical for plants focused on cost efficiency. Overall, the lagoon method stands out as a practical solution for managing sludge economically in lime-soda ash softening plants.