AWWA JAW10212

Samples of groundwater, surface water, secondary effluent, and fulvic acid were treated in laboratory experiments by alum coagulation and lime softening in conjunction with prechlorination and postchlorination. Coagulation and softening both removed significant amounts of nonvolatile organic chlorine, precursors of organic chlorine, and total organic carbon (TOC). Organic chlorine precursors were removed as well as or better than TOC and much better than the organic chlorine formed during prechlorination. The increase in pH during lime treatment hydrolyzed a significant fraction of the nonvolatile organic chlorine, releasing chloroform and other byproducts. The following conclusions are made by the authors: storage of samples at 4 C and pH 2.0 effectively preserves samples for nonpurgeable organic chlorine (NPOCl) analysis; prechlorination results in higher values of NPOCl in finished waters as compared to postchlorination when samples are treated by alum coagulation; lime softening hydrolyzes a significant amount of NPOCl to chloroform and other by-products; and removal of TOC is a conservative indicator of NPOCl removal for postchlorinated samples but is not a good indicator for prechlorinated samples. Includes 26 references, tables, figures.