Evaluation of the treatment performance of a multistage ozone/hydrogen peroxide process by decomposition by-products

The performance of a multistage ozone/hydrogen peroxide (O-3/H2O2) process was evaluated with respect to total organic carbon (TOC) removal of waste w aters, An aqueous humic acid solution (5.2 mg Cl-1 as TOC) and a sand filte red secondary sewerage effluent (5.6 mg Cl-1 as TOC) were used as model was te waters. Appropriate range of hydrogen peroxide (H2O2) dose at each stage depended upon the components of the tested solutions that changed as the p rocess proceeded. Higher hydrogen peroxide dose was required at later stage s in which low reactivity compounds with hydroxyl radical (HOcircle), low m olecular fatty acids, were predominant. And, oxalic acid concentration rela ted to H2O2 demand at later stages. This was assumed that the slow decompos ition of oxalic acid was rate-determining step for TOC removal after its ac cumulation, Also, it is important to maintain dissolved ozone at low concen tration for efficient TOC removal because rapid ozone consumption is requir ed for the rapid formation of hydroxyl radical (HOcircle). (C) 2001 Elsevie r Science Ltd. All rights reserved.