Author(s): Maria Jesus Abeledo-Lameiro; Alba Hernandez Zanoletty; Samira Nahim-Granados; Maria Inmaculada Polo-Lopez; Isabel Oller; Sixto Malato

Linked Author(s): María Jesús Abeledo-Lameiro

Keywords: Hydrogen peroxide; EDDHA; Persulfate; Contaminants of emerging concern-CEC; Sunlight; Microbial indicators

Abstract: In the last years, research on the capability of different solar processes as potential urban wastewater (UWW) tertiary treatment has gained attention. Solar photo-Fenton with iron-quelates (such as Fe³+-EDHHA) and other solar driven chemical processes based on the use of oxidative agents (such as hydrogen peroxide (H₂O₂) or persulfate (PDS)) have proven good efficiency for the abatement of pathogenic microorganisms and hazardous chemical compounds from secondary effluents of UWW. Moreover, its application within CPC reactor is an effective solution that promote the collection of UV-visible photons from solar radiation, accelerating any water disinfection and decontamination process. This study aims to evaluate different solar processes (H₂O₂, PDS, and solar photo-Fenton with Fe³+-EDHHA in combination with H₂O₂ or PDS) for the simultaneous decontamination and disinfection of actual secondary effluents from the UWW treatment plant of “El Bobar” (Almería, Spain). Freshly and physicochemical characterized batches of UWW were treated using a CPC reactor (Total volume 18L, illuminated volume 12.5 L, illuminated surface 1 m²) in recirculation mode. Naturally occurring Escherichia coli, Total coliforms and the virus’s somatic coliphages (SOMCPH) in UWW were monitored as microbial indicators; meanwhile a cocktail of CEC (sulfamethoxazole, pyrimethanil and pentachlorophenol) spiked in the UWW at 100 µg/L each were assessed as a model of chemical pollutants. The following solar treatments and oxidant concentrations (selected according to previous works) were tested: a) 50 mg/L-H₂O₂; b) 2.5/20 mg/L-Fe³+-EDHHA/H₂O₂; c) 0.5, 0.7 and 1mM-PDS; d) 2.5 mg/L-Fe³+-EDHHA with 0.5 and 1 mM-PDS. The solar treatment times lasted for four hours, along which water temperature and solar UVA radiation were also monitored. Decontamination results showed that after 240 min of treatment time, no significant differences in the degradation of ∑CECs were observed, reaching a removal of 70-80 % with all treatment and conditions investigated. Regarding water disinfection, the best treatment for bacterial inactivation (3-LRV of E. coli and 4-LRV of Total coliforms, detection limit 200 CFU/100 mL) was obtained with Fe³+-EDHHA/H₂O₂ (90-120 min), followed by H₂O₂/solar (120 min), and PDS/solar (150-180 min), respectively. Nevertheless, a different performance trend was observed for SOMCPH, where 2-LRV (from 535-1280 to 2 PFU/100 mL) was reached only for H₂O₂/solar and PDS/solar (0.5 and 1 mM) after 150, 180, and 240 min treatment time, respectively. Summarizing, the best treatment for the simultaneous disinfection and decontamination of actual UWW was determined with H₂O₂/solar at a concentration of 50 mg/L. At this condition, water quality obtained meets the requirements established in the new European regulation on wastewater for irrigation in agriculture (EU 2020/741), nevertheless, higher concentrations of these oxidants are being currently investigated in order to improve the treatment time and evaluating also their response against other pollutants concern, such as antibiotic resistant genes.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022909

Year: 2022