The effect of water treatment processes on the biological stability of potable water

The AOC (assimilable organic carbon) method was used in this study to evalu ate the biological stability of potable water. The potable water was drawn from a waterworks located in a petrochemical industrial area in China. Infr ared spectra analysis was adopted in this study to examine the relationship between treatment process and organic compounds in water. By monitoring th e AOC concentration in groundwater, potable water and the effluent of each treatment process (biological pretreatment, ozonation, GAC adsorption), the following were noted: (1) a considerable AOC concentration could still be detected in potable water after advanced treatment processes, such as ozona tion and activated carbon adsorption. Relatively poor biological stability was also noted in the potable water; (2) GAC was the most effective process with a total AOC removal efficiency of more than 80%. The corresponding bi otreatment removal efficiency was only 45%. However, ozonation yielded a ne gative overall removal efficiency of -119%; (3) while biological pre-treatm ent and GAC adsorption contributed towards a biologically stable water, ozo nation yielded oxidation products which were biologically unstable. Ozonati on, if used, should therefore be combined with the GAC or biological proces ses. Treatment processes (like ozonation) which increased the amount of org anics in carbonyl group would likely lead to poor product water biological stability. (C) 1999 Elsevier Science Ltd. Ail rights reserved.