Removal of sulfamethoxazole and diclofenac from water: strategies involving O₃ and H₂O₂

ABSTRACT

Diclofenac (DCF) and Sulfamethoxazole (SMX) are two of the most frequently detected pharmaceutical compounds in water and are hardly removed by biological treatment systems. The presence of H₂O₂ was investigated in the ozonation of these two compounds. Experiments were carried out with both using distilled water and secondary effluent from a municipal wastewater treatment plant spiked with pharmaceuticals. Chemical oxygen demand (COD) abatement rate improved when H₂O₂ was added at the beginning of the ozonation process and when the ozone inlet concentration increased, attaining a maximum value of 91% and simultaneously a lower ozone waste for a H₂O₂ initial concentration of 5 mM and an ozone inlet concentration of 20 g Nm⁻³. For these operation conditions, the water matrix has no significant impact on SMX and DCF removal, which were totally degraded in 45 and 60 min, respectively. Nevertheless, lower COD degradation and ozone usage were obtained when the secondary effluent was used. Inorganic ions such as chloride, sulphate and nitrate and short-chain organic compounds were detected as by-products of the SMX and DCF oxidation. Vibrio fischeri luminescence inhibition tests revealed that simultaneous use of ozone and H₂O₂ reduced acute toxicity.

KEYWORDS:

• Emerging contaminants
• pharmaceuticals
• sulfamethoxazole
• diclofenac
• ozonation

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Rui C. Martins gratefully acknowledges Fundação para a Ciência e a Tecnologia for the financial support via the IFCT 2014 programme [IF/00215/2014].