Aldehydes formation in the treatment of humic acid by Ozone/GAC hybrid process

The formation of aldehydes as by-product was investigated in the treatment of humic acid by Ozone/GAC hybrid process. Ozone/GAC hybrid process was operated under varying initial pH (pH 3 similar to pH 11) and temperature (0 degrees C, 20 degrees C, 40 degrees C) at an ozone dose of 0.08 g O3/g DOC and GAC amount of 16.5 v/v%. The results were compared with those of GAC adsorption and ozone alone process. The formed aldehydes were derivatized by PFBOA method and quantified by GC/PDECD. Formaldehyde and glyoxal were identified as the substantial aldehydes in the treatment of humic acid by ozone/GAC hybrid process. Quantities of formaldehyde and glyoxal formed in ozone/GAC hybrid process were less than one in ozone alone process. In ozone/GAC hybrid process, formaldehyde was produced with a considerable concentration of 400 ppb at pH 11 and pH 7 at the beginning of the treatment, and then the concentration was decreased with time. And, the concentrations of formaldehyde and glyoxal were increased with an increase of temperature. They were respectively 520 ppb and 120 ppb at the beginning of the treatment at 40 degrees C.