Ing Civil

Oxidation of sulfamethoxazole by UVA radlation and
modified Fenton reagent: toxicity and biodegradabjljty
of by-products
Marcíocha, J. Kalka, J. Turek-Szytow, J. Wiszniowskl
d J. Surmacz-Górska

ABSTRACT
Improvement of sulfamethoxazole (4-amino-N (5-methyIisoxazoI-3-yl)-benzenesuIfonamide-SMX) biodegradability using a modified Fenton’s reaction has been studied. The modificationconsists
of replacing hydrogen peroxide with atmospheric air and adding copper sulphate as a reaction promoter. Two series of experiments were carried out. The first (Series 1) was conducted using only the catalysts with aeration. In the second series (Series 2), cycles of UVA radiation and aeration were used. During UVA radiation, the removal of Sulfamethoxazole proceeds less rapidly
than inonly aerated solution. After 1.5 h of these two processes, the SMX degradation was 23% Series 2 and 59% in Series 1. The Opposite trend was observed for mineralization and the removal of DOC was about 5% higher in Series 2 than in Series 1.The FTIR spectra of the extracts of reaction products yielded by four organic solvents of varying polarity revealed a wide diversity of functional groups in thepost-reaction mixture in comparison to the extracts from sulfamethoxazole solution. Based on FTIR analysis, several oxidation products of sulfamethoxazole are proposed. Apparently, hydroxyl radicals initially attack sulphonamide bonds, resulting in the formation of sulfanilic acid and 3-amino-5-methylisoxazole.Irrespective of the
reference organism used in toxicity tests, tile post-reactionmixture in the Series 2 was more toxic than the post-reaction mixture in Series 1. In contrast, the biodegradability calculated as BOD5/DOC ratio, was higher for post-reaction mixture 2 and amounted to 0.43.

Key words │bioassays, FTR, modified Fentons reaction, sulfamethoxazole, UV—radiation

INTRODUCTION

The widespread presence of drugs, pharmaceuticals and
their metabolites in surfacewater or even in drinking
water is raising public health concerns (Ternes 1998;
Kummerer 2004).
Overuse of broad-spectrum- antibiotics,
improper use of antibiotics by patients as well as the use
antibiotics as livestock food additives for growth
promotion, greatly hastens bacterial resistance. The emergence and spread of bacteria resistant to multiple antibiotic drug classes hasresulted in considerable attention being paid to elucidating the role of antimicrobial agents in the environment.
One of these, Sulfamethoxazole (4-anlino-N-(5-methyl isoxazol.3.y1) benzenesulfonamide_SMX), which belongs to the group of sulfonamides, is a synthetic antimicrobial agent derived from sulfanilic acid. In Poland, approximately 6 tons of SMX—a prescription drug are sold annually (NationalMedicines Institute, Warsaw, unpublished data 2004). Sulfamettiuxazole is widely used in hospitals to treat human infections, such as typhus, carrier state treatment, prostate gland or urinary tract infections. After use, the substance is metabolized in the liver and its unchanged form (about 20% of the applied dose) is excreted with the urine (Podlewskj & 1999).

The recent studies ofGobel et al. (2007) confirm that the removal of SMX during wastewater treatment ranges from 60% in a conventional activated sludge system to 80% in a membrane bioreactor. As a result, substantial residual amounts of SMX can enter the environment with the treated wastewater effluents.

Since a significant amount of SMX is excreted with the urine, a selective source separation (for instance inhospitals) and pre-treatment might decrease the amount of sulfamethoxazole entering the water cycle considerably. The option for separation and treatment of concentrated waste streams at the source has been intensively discussed by Ternes & Joss 2006.

Nowadays, there is a growing interest in the development of innovative, economic wastewater technologies designed to eliminate pharmaceuticals...