Transformation of Acesulfame During Ozone-based Advanced Oxidation Process

The artificial sweetener acesulfame (ACE) is widely used in considerable amounts in foodstuffs and consumer products. Chemically, it is remarkably stable, which means it passes through many domestic sewage treatment processes and readily enters the environment. Compared to other sweeteners, ACE has the highest occurrence in environmental compartments worldwide, raising comparable concern. ACE can be degraded by powerful chemical disinfection treatments such as UV photolysis, chlorination, chloramination and ozonation. However, these processes have been shown to be either (a) ineffective, in that they cannot completely degrade ACE; or (b) unsatisfactory, in that they produce some disinfection byproducts (DBPs) or formation of regulated DBPs/nitrogenous-DBPs or even carcinogenic N-nitrosodimethylamine (NDMA) that more toxic than ACE itself. Ozone/hydrogen peroxide (O3 /H2 O2 )-based advanced oxidation processes (AOPs), i.e. oxidation processes using ozone and hydrogen peroxide, might be able to remove ACE. Indeed, ozone treatment is already widely used and highly regarded throughout Europe (France, Italy, Greece and Switzerland), Asia (China and Japan), America, and Australia. However, whether O3 /H2 O2 treatment of ACE is a desired resolution without biological hazards from the generated DBPs is still a pending question. At this stage, details of the transformation fate and related biological impact of ACE DBPs from O3 /H2 O2 treatment remain largely unknown. Our preliminary degradation study has revealed a progressive change of molecular profile and formation of several known and previously unknown ACE DBPs. Research that can decipher the chemical mechanism and assess the toxicity of ACE DBPs during the O 3 /H2 O2 process is therefore of pivotal importance to safe, effective drinking water treatment.

To this end, the present work will trace the chemical transformation of ACE undergoing O3 /H2 O2 treatment. Chemical structures and identities of individual ACE DBP will be confirmed by comprehensive instrumental characterizations. Chemical data obtained will be used to establish the O3 /H2 O2 -induced degradation mechanism. Key parameters of peroxide dosage, initial pH and the presence of tert-butyl alcohol will be quantified with regard to their influence on ACE oxidation. Biological testing will be carried out to thoroughly evaluate the impact of ACE DBPs on drinking water safety. Finally, the evolution of ACE DBPs will be screened in the water produced at treatment plant and in household water to verify that the O3 /H2 O2 treatment has in fact removed ACE.

The chemical and toxicological data produced in this study, will provide details of the transformation, fate and related biological impact of ozone-hydrogen peroxide-based oxidation disinfection, specifically with regard to the contaminant ACE. If successful, the process tested here would inform efforts to design and develop better disinfection methods for our most vital resource, water, particularly with regard to one of the most serious and increasingly problematical chemicals currently contaminating water supplies.