Feasible and economical methodologies were needed to remove existing organic contaminants--specifically, four trihalomethanes (chloroform, bromodichloromethane, chlorodibromomethane, and bromoform)--from and prevent development of potential carcinogens in the public water supplies in Dade County, Florida. A four-phase study was designed to evaluate the efficiency of three adsorbents in removing 19 individual halogenated organics and trihalomethane precursors. These adsorbents were XE-340--a carbonized polymeric macroreticular resin; IRS-904--a strong base catonic resin designed to remove large molecular weight substances such as precursors from water; and granular activated carbon (GAC). Appendix A contains the preliminary studies made of the bacterial profile of raw and finished water and effluent from four GAC columns from the Preston Water Treatment Plant. Raw water organisms, which apparently can survive existing treatment plant processes, colonized the initially bacteria-free GAC columns and released vast numbers of bacteria into the water flowing through the columns. The development of bacterial growth in the GAC columns interfered with backflushing the columns.