Author(s): Paula Nunez Tafalla; Irene Salmeron; Silvia Venditti; Joachim Hansen

Linked Author(s):

Keywords: Dvanced Oxidation Process; Contaminants Emerging Concern; Pilot plantReal wastewater

Abstract: In recent years the growth of the chemical industry attending the increasing demand for herbicides, pesticides and pharmaceuticals has led to the appearance of substances in the environment at trace concentrations called microcontaminants (MCs) that cannot be removed from wastewater by the conventional biological processes applied at wastewater treatment plants (WWTP). Consequently, they remain in the discharged effluents with the potential risk that could entail for the flora and the fauna. Thus, the implementation of new technologies for their targeted and cost-efficient removal is a challenge that needs to be addressed. In this context, the Water Management Authority of Luxembourg has selected thirteen WWTP to implement advanced technologies as a latest step to reduce the presence of MCs on the effluents, establishing the 80% of removal regarding the WWTP influent as goal. Four MCs were selected as relevant compounds: benzotriazole, carbamazepine, clarithromycin and diclofenac. The combination of photo-Fenton process and Granular Activated Carbon (GAC) has been rarely reported, even less under near-real conditions, working at natural pH at pilot-scale. This work addresses their combination as a feasible alternative for medium-small size WWTP aiming their implementation at Heiderscheidergrund WWTP (12 000 population equivalent, Esch-sur-Sûre, Luxembourg) for reduce energy consumption of photo-Fenton and increase lifetime of GAC. Photo-Fenton equipment consisted of 500W medium pressure lamp (UV power 89W), connected to a storage tank with a total working volume of 60 L. The lamp was installed on a 1.2 L reactor with 0.1 m2 of illuminated area. The further GAC treatment was tested through Rapid Small Scale Columns consisting of two glass columns (8 mm diameter and 100 mm length) with different bed volumes possibilities operated in parallel. Two GAC types have been assessed, Norit 830 and NRS Carbon GA 0.5–2.5 (regenerated) that pose a green alternative due to its lower cost and carbon footprint. The optimization of operational parameters was performed via response surface methodology working at natural pH and selecting the optimal variables looking to scaling up. On the photo-Fenton the variables were the reagents (H₂O₂ and iron) dosage (using a chelating agent to maintain iron in solution at circumneutral pH). Results showed that the best dosage was 5 mg/L or iron and 40 mg/L of H₂O₂ reaching an 87% elimination after 20 minutes. For the combination, the effluent obtained after 5 and 10 minutes of photo-Fenton was post-treated with GAC, achieving the 80% after 4 and 1 hour respectively. Results showed that the combination of treatments supposes a reduction of photo-Fenton time, entailing an energy consumption reduction of 75 and 50% for 5 and 10 minutes respectively. The process has been demonstrated as feasible and next step is to carry out a cost analysis to assess its viability.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221656

Year: 2022