disclosed herein are systems and process integrating the chemical - free oxidation of a photocatalytic decontamination process with a biological decontamination system to eliminate the thm and haa precursors in drinking water . in one embodiment , a system may comprise a source providing fluid media contaminated with toxic natural organic matter , and a photocatalytic decontamination subsystem configured to oxidize the toxic natural organic matter via a photocatalytic process into non - toxic natural organic matter having a molecular weight low enough for biodegrading said non - toxic matter . the system may include a biological decontamination subsystem configured to immediately receive the contaminated fluid output from the photocatalytic decontamination subsystem , and employing a biological agent to biologically degrade the low - molecular weight non - toxic natural organic matter in the contaminated fluid to a concentration sufficient to prevent the formation of trihalomethanes or haloacetic acids . also , such a system may include a disinfectant sub - system configured to disinfect the fluid output from the biological decontamination subsystem .