Removing soluble organic contaminants by lime‐softening

Lime–soda softening effectively removed several humic substances from solution, including a fulvic acid isolated from a local groundwater supply. Removal increased with increased pH, increased amounts of precipitate, and decreased concentrations of TOC and was enhanced significantly by the presence of magnesium or phosphate, especially when a small amount of precipitate was formed. Lime–soda softening achieved at least partial removal of several soluble organic chemicals, although some were not removed to any significant extent. Soluble calcium caused the precipitation of several organic substances in the absence of carbonate ion, indicating that precipitation is a potential removal mechanism. Experimental evidence for other removal mechanisms is discussed.