Abstract
Parallel studies using Ozonation-Biological Activated Carbon (O3-BAC) process and a simple Biological Activated Carbon (BAC) process were conducted to evaluate the effect of ozonation on a BAC process. The raw water used was pre-treated by microfiltration to remove suspended solids. Contact time for ozonation was 24 minutes while empty bed contact time (EBCT) of the activated carbon column was 15 minutes. An ozone dosage of 7 mg·l-1 was used.
Effluent DOC and THMFP of O3-BAC process were lower than those of BAC process after 80 days. Lifetime of activated carbon adsorption was extended in the O3-BAC process compared with the BAC process until breakthrough, because ozonation decreased DOC in the activated carbon influent in the O3-BAC process. DOC was partitioned into four fractions and analyzed based on its biodegradability and activated carbon adsorbability. It is proposed that O3-BAC process can be used for a long time without activated carbon replacement because biodegradable DOC was removed even after activated carbon adsorption capacity was exhausted. Adsorbed DOC in the O3-BAC process also decreased until breakthrough, probably because ozonation increased hydrophilicity of DOC resulting in its decreasing adsorbability. In this study, ozone dosage of 2 mg O3·mg DOC-1 and EBCT of 15 minutes was determined to be satisfactory for an increase in biodegradability and removal of DOC.
