Combination of the Electro/Fe3+/peroxydisulfate (PDS) process with activated sludge culture for the degradation of sulfamethazine

- The Electro/Fe3+/Peroxydisulfate process was used for degradation of sulfamethazine.
- 40 mA/cm2 current density and 0.18 mM of SMT concentration were the optimal values.
- Optimal concentrations of PDS and Fe3+ were 10 mM and 1 mM, respectively.
- The by-products formed after 6 h of electrolysis were biodegradable.
- The subsequent biological treatment increased the mineralization yield to 86%.

In this paper, the major factors affecting the degradation and the mineralization of sulfamethazine by Electro/Fe3+/peroxydisulfate (PDS) process (e.g. current density, PDS concentration, Fe3+ ions concentration and initial sulfamethazine (SMT) concentration) were evaluated. The relevance of this process as a pretreatment prior to activated sludge culture was also examined. Regarding the impact on SMT degradation and mineralization, the obtained results showed that they were significantly enhanced by increasing the current density and the PDS concentrations in the ranges 1-40 mA cm−2 and from 1 to 10 mM respectively; while they were negatively impacted by an increase of the initial SMT concentration and the Fe3+ concentration, from 0.18 to 0.36 mM and from 1 to 4 mM respectively. The optimal operating conditions were therefore 40 mA cm−2 current density, 10 mM PDS concentrations, 1 mM Fe3+, and 0.18 mM SMT. Indeed, under these conditions the degradation of SMT and its mineralization yield were 100% and 83% within 20 min and 180 min respectively. To ensure a significant residual organic content for activated sludge culture after Electro/Fe3+/PDS pre-treatment, the biodegradability test and the biological treatment were performed on a solution electrolyzed at 40 mA cm−2, 10 mM PDS concentrations, 1 mM Fe3+, and 0.36 mM SMT. Under these conditions the BOD5/COD ratio increased from 0.07 to 0.41 within 6 h of electrolysis time. The subsequent biological treatment increased the mineralization yield to 86% after 30 days, confirming the relevance of the proposed combined process.

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