A Pilot Study Combining Ultrafiltration with Ozonation for the Treatment of Secondary Urban Wastewater: Organic Micropollutants, Microbial Load and Biological Effects

Abstract

Ozonation followed by ultrafiltration (O3 + UF) was employed at pilot scale for the treatment of secondary urban wastewater, envisaging its safe reuse for crop irrigation. Chemical contaminants of emerging concern (CECs) and priority substances (PSs), microbial load, estrogenic activity, cell viability and cellular metabolic activity were measured before and immediately after O3 + UF treatment. The microbial load was also evaluated after one-week storage of the treated water to assess potential bacteria regrowth. Among the organic micropollutants detected, only citalopram and isoproturon were not removed below the limit of quantification. The treatment was also effective in the reduction in the bacterial loads considering current legislation in water quality for irrigation (i.e., in terms of enterobacteria and nematode eggs). However, after seven days of storage, total heterotrophs regrew to levels close to the initial, with the concomitant increase in the genes 16S rRNA and intI1. The assessment of biological effects revealed similar water quality before and after treatment, meaning that O3 + UF did not produce detectable toxic by-products. Thus, the findings of this study indicate that the wastewater treated with this technology comply with the water quality standards for irrigation, even when stored up to one week, although improvements must be made to minimise microbial overgrowth.

Performance of polycarbonate, cellulose nitrate and polyethersulfone filtering membranes for culture-independent microbiota analysis of clean waters

“…DNA was extracted with a commercial kit (DNeasy® PowerWater® Kit, QIAGEN, Hilden, Germany), simultaneously from all filtering membranes and by a single operator. The procedure was described before [2], including two additional steps to improve bacterial lysis and to promote the removal of residual ethanol before DNA elution. DNA concentrations (ng/μL) were determined with Qubit (Thermo Fisher Scientific, USA).…”

“…Yet, the evaluation of the microbiota composition in this type of water is important to assess treatment efficiency, water quality and safety stability. This is the case of the development of novel water disinfection technologies or the optimization of water reuse procedures in agriculture or industrial processes [2][3][4]. The use of culture-independent approaches to this end, instead of culture-based methods, has important advantages as it can also survey non-culturable bacteria [5,6].…”

Reuse of effluents from cattle slaughterhouses: multicriteria evaluation

“…For removing E. coli, the technologies of ozonation stand out with 99% removal and ultrafiltration with 99.98% removal (Bertolossi et al, 2021). The combined process of ultrafiltration with ozonation for wastewater treatment is effective in reducing the microbial load (Graça et al, 2020).…”

Spirulina-based carbon bio-sorbent for the efficient removal of metoprolol, diclofenac and other micropollutants from wastewater

“…Wastewater (WW) samples were collected from the secondary treatment tanks of an UWWTP located in northern Portugal. The characterization of this WW has already been reported in previous studies of our group [48,49]. The WW was filtered through 1.2 μm glass-fiber filters (47 mm GF/C, Whatman™, Maidstone, United Kingdom) to remove suspended solids and then frozen until usage.…”