Assessment of different iron sources for continuous flow solar photo-Fenton at neutral pH for sulfamethoxazole removal in actual MWWTP effluents

This study addresses the comparison of three iron sources to remove sulfamethoxazole (SMX) at 50 mu g/L as a surrogate contaminant of emerging concern by continuous flow solar photo-Fenton at neutral pH in secondary effluents from two wastewater treatment plants. Experiments were conducted in a stirred tank reactor with a liquid depth of 5 cm, using two ferric iron complexes (0.1 mM), with ethylenediamine-N,N-disuccinic acid (EDDS) and nitrilotriacetic acid (NTA) as chelating agents, and FeSO4 (0.36 mM). In this regard, this is the first time Fe3+-NTA has been used in the continuous operation of the photo-Fenton process. On the one hand, Fe3+EDDS led to the highest SMX removal (around 60 %) in both effluents at hydraulic residence times of 30 and 60 min, respectively. On the other hand, wastewater composition significantly affected reagent consumption and, consequently operating costs. In terms of cost efficiency of SMX removal, the order was Fe3+-NTA (3.25-7.81 mgSMX/m3.euro) > FeSO4 (2.03-5.09 mgSMX/m3.euro) > Fe3+-EDDS (1.12-2.48 mgSMX/m3.euro).

Automated summary

This study compared three iron sources for removing sulfamethoxazole in secondary effluents from two wastewater treatment plants using continuous flow solar photo-Fenton. Fe3+-EDDS achieved the highest SMX removal in both effluents, while wastewater composition significantly affected reagent consumption and operating costs. The cost efficiency of SMX removal was highest for Fe3+-NTA, followed by FeSO4 and Fe3+-EDDS.