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

Abstract

The AOC (assimilable organic carbon) method was used in this study to evaluate the biological stability of potable water. The potable water was drawn from a waterworks located in a petrochemical industrial area in China. Infrared spectra analysis was adopted in this study to examine the relationship between treatment process and organic compounds in water. By monitoring the 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 ozonation 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 biotreatment removal efficiency was only 45%. However, ozonation yielded a negative overall removal efficiency of -119%; (3) while biological pre-treatment and GAC adsorption contributed towards a biologically stable water, ozonation yielded oxidation products which were biologically unstable. Ozonation, if used, should therefore be combined with the GAC or biological processes. Treatment processes (like ozonation) which increased the amount of organics in carbonyl group would likely lead to poor product water biological stability.