Laboratory for Process Engineering, Environment, Biotechnology and Energy

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Publications

Removal of microorganisms and antibiotic resistance genes from treated urban wastewater: a comparison between aluminium sulphate and tannin coagulants

Publication . Grehs, Bárbara W. N.; Lopes, Ana Rita; Moreira, Nuno F. F.; Fernandes, Telma; Linton, Maria A. O.; Silva, Adrián M. T.; Manaia, Célia M.; Carissimi, Elvis; Nunes, Olga C.

The presence of antibiotic resistant-bacteria (ARB) and antibiotic resistance genes (ARG) in treated effluents of urban wastewater treatment plants (WWTP) may represent a threat to the environment and public health. Therefore, cost-effective technologies contributing to minimize loads of these contaminants in the final effluents of WWTP are required. This study aimed at assessing the capacity of coagulation to reduce the ARB&ARG load in secondary treated urban wastewater (STWW), as well as the impact of the process on the structure and diversity of the bacterial community. Coagulation performance using aluminium sulphate, a synthetic substance, and tannins, a biowaste, was compared. Samples were analysed immediately before (STWW) and after the coagulation treatment (Alu, Tan), as well as after 3-days storage in the dark at room temperature (RSTWW, RAlu, RTan), to assess possible reactivation events. Both coagulants decreased the turbidity and colour and reduced the bacterial load (16S rRNA gene copy number, total heterotrophs (HET), and ARB (faecal coliforms resistant to amoxicillin (FC/AMX) or ciprofloxacin (FC/CIP) up to 1–2 log immediately after the treatment. Both coagulants reduced the load of intl1, but in average, aluminium sulphate was able to decrease the content of the analysed ARGs (blaTEM and qnrS) to lower levels than tannin. Reactivation after storage was observed mainly in RTan. In these samples the load of the culturable populations and qnrS gene prevalence increased, sometimes to values higher than those found in the initial wastewater. Reactivation was also characterized by an increment in Gammaproteobacteria relative abundance in the bacterial community, although with distinct patterns for RTan and RAlu. Curvibacter, Undibacterium and Aquaspirillum were among the most abundant genera in RAlu and Aeromonas, Pseudomonas and Stenotrophomonas in RTan. These bacterial community shifts were in agreement with the variations in the culturable bacterial counts of HET for RTan and FC/CIP for RAlu. In summary, the overall performance of aluminium sulphate was better than that of tannins in the treatment of treated urban wastewater.

2019Journal article

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Heterogeneous photocatalysis using UVA-LEDs for the removal of antibiotics and antibiotic resistant bacteria from urban wastewater treatment plant effluents

Publication . Biancullo, Francesco; Moreira, Nuno F. F.; Ribeiro, Ana R.; Manaia, Célia M.; Faria, Joaquim L.; Nunes, Olga C.; Castro-Silva, Sergio M.; Silva, Adrian M. R.

Secondary urban wastewater samples were spiked with azithromycin (AZT), trimethoprim (TMP), ofloxacin (OFL) and sulfamethoxazole (SMX) at 100 mu g L-1 to investigate the efficiency of a TiO2-photocatalytic treatment using UVA-LEDs. Different operating parameters were studied, such as the irradiation conditions, catalyst load and the use of methanol as carrier solvent and radical scavenger. The most efficient conditions to treat spiked urban wastewater (4 LEDs symmetrically distributed and 1.00 g L-1 of catalyst) were also assessed on the removal of the antibiotics at real concentrations, as well as on the inactivation and regrowth of bacteria after 3-day storage (total and resistant heterotrophs, Escherichia coli and enterococci). Clindamycin (CLI) was targeted when SMX was not detected. One-hour treatment was enough to reduce the analysed antibiotics to values below the detection limits and to decrease the bacterial load by 2 log-units. Bacterial regrowth was observed for total heterotrophs, after the storage of photocatalytic treated wastewater, to values close to pre-treatment. However, the antibiotic resistance percentage of such stored wastewater was always similar or lower than that of secondary urban wastewater. Thus, the potential of this process as part of the tertiary treatment is demonstrated, but conditions must be adjusted to minimize microbial regrowth.

2019Journal article

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High efficient strategy for the production of hydroxyapatite/silk sericin nanocomposites

Publication . Veiga, Anabela; Castro, Filipa; Oliveira, Ana L.; Rocha, Fernando

BACKGROUND: Sericin (SS) induces nucleation of bone-like hydroxyapatite (HAp) when used as an organic matrix. HAp/SS nanocomposites have been conventionally synthesized through precipitation in stirred tank reactors (STs). Despite its simplicity, this process is time consuming and presents difficulties in scale-up. In our study, HAp/SS nanocomposites were successfully synthesized in a ST and in a meso-oscillatory flow reactor (meso-OFR), to compare the efficiency of both reactors and to study HAp mineralization using SS as a template. RESULTS: The production of stable HAp, indicated by pH stabilization, was achieved after 180 min in the ST and after 30 min in the meso-OFR. X-ray diffraction and Fourier transform infrared analyses showed that the particles obtained in both reactors are HAp/SS nanocomposites with low crystallinity. Scanning electron microscopy evidenced the formation of rod- and plateshaped nanoparticles and revealed that the presence of SS led to the production of larger particles. The latter observation was confirmed by laser diffraction. Additionally, increasing SS concentration resulted in the formation of more plate-like particles. CONCLUSIONS: Precipitation is more efficient in the meso-OFR, HAp/SS being obtained four times faster. The presence and concentration of SS led to differences in the size and morphology of the synthesized particles, suggesting a critical role of SS in the mineralization process. This work reports a new approach for the manufacture of high-added-value nanocomposites with similar characteristics to biological bone and the results of a study of the influence of SS as an organic component in HAp nucleation. Further, the use of this protein and technology leads to significant waste minimization.

2020Journal article

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Ultrafiltration after ozonation of urban wastewater: tackling bacterial regrowth

Publication . Soares, S. R.; Graça, C. A. L.; Abreu-Silva, J.; Manaia, C. M.; Ribeiro, A. R.; Silva, A. M. T.; Nunes, O. C.

2019Conference object

Open access

Hydroxyapatite/sericin composites: A simple synthesis route under near-physiological conditions of temperature and pH and preliminary study of the effect of sericin on the biomineralization process

Publication . Veiga, Anabela; Castro, Filipa; Cunha-Reis, Cassilda; Sousa, Aureliana; Oliveira, Ana; Rocha, Fernando

Synthesis of hydroxyapatite (HAp) and sericin (SS) nanocomposites was carried out by a simple precipitation method performed in batch in a stirred tank reactor (ST). The reaction was achieved by mixing a solution of calcium chloride dihydrate, in which SS was dissolved, with a solution of disodium hydrogen phosphate at 37 °C. Three experimental conditions were studied by varying the concentration of SS: HAp, HAp/SS1 (0.01 g/L of SS) and HAp/SS2 (1 g/L of SS). The chemical and physical properties of the resulting HAp/SS nanocomposites were studied using several techniques (Atomic Absorption Spectrometry, Ultraviolet-Visible Spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Selected area diffraction (SAED) and Thermogravimetric analysis (TGA)). pH profile was also monitored over time for each experimental condition. The results revealed that nano single-phased HAp was formed with both rod and plate-like shape. Additionally, the particles have low crystallinity, characteristic similar to biological HAp. Regarding the influence of SS, one observed that with increasing SS concentration there is an increase in the mean particle size and the number of plate-like particles, as well as an increase in the aggregation degree and a decrease of the crystallinity. Further, the composites obtained have an inorganic/organic composition comparable to bone. Finally, in vitro cytotoxicity showed that the synthetized nanoparticles are non-toxic and cell viability is higher for HAp and HAp/SS samples when compared to a commercially available HAp. The produced materials can thus be considered suitable candidates for bone related applications.

2020Journal article

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