The presence of external chloride can lead to a 47-fold increment in degradation rates of 4-chlorophenol than those in the absence of chloride in UV/peroxymonosulfate process. The other side of the same coin is an undesirable accumulation and increase in absorbable organic halogen (AOX) was observed in the presence of chloride, with formation of some more toxic tetrachlorinated byproducts.
