An organic contaminant from coagulants would most likely include which compound?

• A. epichororhydrin
• B. Polynuclear aromatic hydrocarbons
• C. Polychlorinated biphenyls
• D. Tetrachloroethylene

Answer: (A)

Coagulants used in water treatment can leave behind organic residues that come from the polymer materials or their processing. Epichlorohydrin is commonly involved in making crosslinked polymer coagulants used for flocking and settling. If any epichlorohydrin remains in the finished coagulant or in trace amounts associated with the polymer, it can end up as an organic contaminant in treated water. That makes epichlorohydrin the most likely organic residue from coagulants among the options.

The other compounds are not typical residuals from coagulants: polynuclear aromatic hydrocarbons come mainly from combustion and environmental sources; polychlorinated biphenyls (PCBs) are industrial pollutants no longer used in modern coagulants; tetrachloroethylene is a solvent contaminant rather than a coagulant-related residue.