Removal of haloacetic acids by ozone and biologically active carbon

Haloacetic acids are recognized as carcinogens. They are naturally formed on the surface of water or as disinfection by-products of drinking water during the chlorination process. The efficiency of an integrated treatment system combining ozonation and biological activated carbon (BAC) was examined for the removal of five regulated haloacetic acids, namely, chloroacetic, dichloroacetic, trichloroacetic, bromoacetic, and dibromoacetic acid (known collectively as HAA(5)), in synthetic water. The effects of ozone dosage, contact time during the ozonation process, and the empty bed contact time (EBCT) of the BAC column were also evaluated. The results demonstrate that the ozonation process is not an effective approach to remove HAA(5) since less than 20% of HAA(5) at the concentration levels found in the water supply system was removed. The majority of HAA(5) in the tested solutions were subsequently removed by the BAC column inoculated with bacteria readily available in surface water. More than 90% of the remaining HAA(5) was eliminated after having been passed through the BAC column with an EBCT of at least 20 minutes. Indigenous microorganism communities inoculated in the BAC column were able to degrade individual HAA(5) species without preference.