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In this study, we evaluated indoor air quality to highlight the effects of environmental pollution in the field of cultural heritage. In particular, two important archeological places in the old part of the city of Salerno, Italy, were analyzed: Fruscione Palace and S. Pietro a Corte. The work focused on the influence of tourists on environmental pollution correlated to indoor air quality during some social and cultural events. Moreover, we focused on the possible use of the carbon isotopic composition of CO2 as a tool for environmental studies in the field of cultural heritage. The results showed a good relationship between the isotopic composition of CO2 and the variation of pollutants concentration in the air, demonstrating that it is a valid tool and non-invasive marker to monitor environmental pollution of museums and cultural heritage sites.

Urban Wastewater Treatment Plants (UWTPs) treating mixed urban sewage and industrial wastewater are among the major hotspots for the spread of Antibiotic Resistance Genes (ARGs) into the environment. This study addresses the impact of the wastewater origin on ARG dynamics in a full-scale UWTP (15,000 Population Equivalent, PE) by operating the plant with and without industrial wastewater. Composite samples (4 L) from different treatment points were characterized for their chemical composition, bacterial abundance and for the abundance of four resistance genes against tetracycline, sulfonamides, erythromycin, and quinolones (tetA, sul2, ermB, and qnrS), and of the class 1 integrons (intI1). Although the chemical composition of the outflow significantly differed when the plant operated with or without industrial wastewater, the system efficiency in the removal of bacterial cells, ARGs, and intI1 was constant. The final disinfection by peracetic acid (PAA) did not affect the removal of ARGs, independently of the wastewater origin and the chemical characteristics of the inflows. Our results demonstrated that a well-functioning small size UWTP could treat a significant amount of industrial wastewater mixed in the urban sewage without affecting the overall ARGs and class 1 integrons released into the environment.

In this work permaleic acid (PMA) was investigated as possible disinfecting agent and compared to peracetic acid (PAA) in real tap water and wastewater. Preliminary tests in lysogeny broth (LB) were also performed. PMA was synthesized from maleic anhydride and hydrogen peroxide and, for the first time, its antimicrobial activity was evaluated with respect to the growth inhibition of E. coli. The effect of the pH and bivalent ions, typically occurring in real water matrices (namely, Mg2+ and Ca2+), was also investigated. pKa values for PMA were calculated for the first time by DFT calculations. The concentration of bivalent ions strongly affected disinfection efficiency with PMA (Ca2+=0.33 mgL−1 and Mg2+=0.35 mgL−1: 100% E. coli reduction > log 5; Ca2+=13.3 mg L−1 and Mg2+=25.6 mg L−1: E. coli reduction log 5 E.coli reduction; pH = 9

Solar driven advanced oxidation processes (AOPs) (an alternative solar photo Fenton like process (SPF), sunlight/H2O2 (SHP) and sunlight/chlorine (SCL)) and respective dark conditions, were compared for the first time to conventional (chlorination and UV-C radiation) disinfection processes, in the inactivation of E. coli and Entero strains inoculated in real roof-harvested rainwater (RHRW), to evaluate their possible safe use for crop irrigation. In this regard, bacterial regrowth was also evaluated 6, 12, 24 and 48 h after disinfection treatment. The SPF, using iminodisuccinic acid (IDS)-Cu complex as catalyst, was optimized (H2O2/IDS-Cu 55/1 best molar ratio) under mild conditions (spontaneous pH) and sunlight. The faster inactivation kinetics were observed for the SCL process (k = 1.473 min−1, t1/2 = 0.47 min for E. coli and k = 1.193 min−1, t1/2 = 0.57 min for Entero), while the most effective processes in controlling bacterial regrowth were SPF and SCL. Although UV-C radiation (0–1.3 × 104 μW s cm−2 dose range) was the second faster disinfection process (k = 1.242 min−1, t1/2 = 0.55 min for E. coli and k = 1.150 min−1, t1/2 = 0.60 min for Entero), it was the less effective process in controlling bacterial regrowth (>10 CFU 100 mL−1 already after 6 h post-treatment incubation). According to the bacterial inactivation and regrowth tests carried out in this work, SPF and SCL are interesting options for RHRW disinfection, in case of effluent use for crop irrigation.

In this work, a new green and fully biodegradable (96% after 28 days) catalyst, Fe3+-iminodisuccinate complex (Fe-IDS), was prepared, characterized and applied in Fenton processes (dark and photo-Fenton) for water treatment, using phenol as model organic pollutant. Experiments were performed both in dark and under solar/UV-C radiation to evaluate the effect of the light source and [H2O2] (fixed at 5.3 mM)/[Fe-IDS] ratio on the catalytic degradation of phenol (50 mg L−1). Subsequently, photo-Fenton IDS supported process was compared to other advanced oxidation processes (AOPs) (namely, conventional Fenton at pH 3 and H2O2 photolysis, under solar and UV-C irradiation, respectively). The best results (54% and 49% COD removals for solar and UV-C based processes, respectively) were obtained using a [H2O2]/[Fe-IDS] molar ratio of 250 (R250), corresponding to 0.021 mM of Fe-IDS followed by R500 (0.01 mM of Fe-IDS) and R150 (0.035 mM of Fe-IDS). Process efficiency was in the order solar/Fe-IDS/H2O2 >UV-C/Fe-IDS/H2O2 >Fe-IDS/H2O2 (k = −0.0114, −0.0073 and −0.0018 min−1 respectively) for R250. A complete removal of phenol in terms of COD was obtained for solar/Fe-IDS/H2O2 and UV-C/Fe-IDS/H2O2. Furthermore, the application of Fe-IDS complex for real industrial (olive oil mill) wastewater treatment was also investigated (initial COD in diluted sample 2.4 g L−1). At constant H2O2 concentration (58.82mM), the best performance in terms of COD removal (55%, k = 0.0031 min−1) and biodegradability (BOD5/COD increased from 0.16 to 0.45) was obtained for the condition R150 (0.37 mM of Fe-IDS). Fe-IDS allows to overcome the main limitation (acidic pH) of conventional (photo)Fenton process, making the IDS supported (photo)Fenton an attractive option for water and wastewater treatment in a wide pH range.

In this study, we evaluated indoor air quality to highlight the effects of environmental pollution in the field of cultural heritage. In particular, two important archeological places in the old part of the city of Salerno, Italy, were analyzed: Fruscione Palace and S. Pietro a Corte. The work focused on the influence of tourists on environmental pollution correlated to indoor air quality during some social and cultural events. Moreover, we focused on the possible use of the carbon isotopic composition of CO

The efficiency of a new Advanced Oxidation Process (AOP), namely the photo Fenton like process UV-C/H

Solar photo-Fenton process in raceway pond reactors was investigated at neutral pH as a sustainable tertiary treatment of real urban wastewater. In particular, the effect on antibiotic resistance determinants was evaluated. An effective inactivation of different wild bacterial populations was achieved considering total and cefotaxime resistant bacteria. The detection limit (1 CFU mL−1) was achieved in the range 80–100 min (5.4–6.7 kJ L−1 of cumulative solar energy required) for Total Coliforms (TC) (40–60 min for resistant TC, 4.3–5.2 kJ L−1), 60–80 min (4.5–5.4 kJ L−1) for Escherichia coli (E. coli) (40 min for resistant E. coli, 4.1–4.7 kJ L−1) and 40–60 min (3.9–4.5 kJ L−1) for Enterococcus sp. (Entero) (30–40 min for resistant Entero, 3.2–3.8 kJ L−1) with 20 mg L−1 Fe2+ and 50 mg L−1 H2O2. Under these mild oxidation conditions, 7 out of the 10 detected antibiotics were effectively removed (60–100%). As the removal of antibiotic resistance genes (ARGs) is of concern, no conclusive results were obtained, as sulfonamide resistance gene was reduced to some extent (relative abundance

Treated wastewater discharged into the environment acts as a disturbance of the natural microbial communities in terms of taxonomic composition and of functional gene pool, including antibiotic resistance genes. We tested whether stochastic and heterogeneous site-specific trajectories or generalities, potentially driven by deterministic processes, control the fate of allochthonous bacteria from anthropogenic sources and the persistence of their functional traits in freshwater. Finding generalities would allow the identification of wastewater treatments that could be effective in abating determinants of antibiotic resistance. We analysed the short-term response of native bacterial communities in waters exposed to the disturbance of wastewater at different dilutions, using a metagenomic approach that revealed both microbial community composition and the scope and abundance of the resistome that can pose indirect risks to human health. We found that the taxonomic composition of the communities after the disturbance was driven by case-specific stochastic processes, whereas the resistome had a deterministic trajectory, rapidly stabilising its functional traits with higher proportions of wastewater effluents, regardless of differences in taxonomic composition, richness of antibiotic resistance genes and of bacterial taxa, phenotypic features of the bacterial communities, and type of wastewater treatment. The observed deterministic proliferation of resistomes in freshwater bodies receiving wastewater effluents, suggests that this process may contribute to the global propagation of antibiotic resistance, and thus calls for new legislations promoting alternative tertiary treatments for the wastewater reuse, and targeting bacterial functional traits and not only bacterial abundances.

The efficiency of a new Advanced Oxidation Process (AOP), namely the photo Fenton like process UV- C/H 2 O 2 /IDS-Cu, in removing determinants of antibiotic resistance and pathogenic bacteria was compared to a consolidated AOP (namely UV-C/H 2 O 2 ) in a secondary treated municipal WasteWater (WW). A re- ductionist experimental laboratory-based approach was applied on real WW and the parameters were collected by an alternative integrated approach using (i) flow cytometry to enumerate bacteria and test for the fitness of the bacterial communities and (ii) molecular analyses to define the community com- position (16S rRNA amplicon sequencing) and the abundances of Antibiotic Resistance Genes (ARGs) and of the class 1 integron ( int I1 gene) (by quantitative PCR). The same approach was applied also to post- treatment regrowth tests (24 h) to define the potential persistence of the tested parameters. These exper- iments were performed in both, human pathogens favorable conditions (HPC, in rich medium and 37 °C) and in environmental mimicking conditions (EMC, original WW and 20 °C). UV-C/H 2 O 2 /IDS-Cu process re- sulted to be more effective than the UV-C/H 2 O 2 in inactivating bacterial cells in the EMC post-treatment regrowth experiments. Both AOPs were efficiently abating potential human pathogenic bacteria and ARGs in the HPC regrowth experiments, although this trend could not be detected in the measurements taken immediately after the disinfection. In comparison with the UV-C/H 2 O 2 , the UV-C/H 2 O 2 /IDS-Cu process did not apparently offer significant improvements in the abatement of the tested parameters in the WW effluent but, by evaluating the results of the regrowth experiments it was possible to extrapolate more complex trends, suggesting contrasting efficiencies visible only after a few hours. This study offers a de- tailed view on the abatement efficiency of microbiological/genetic parameters for the UV-C/H 2 O 2 /IDS-Cu process, calling for technical adjustments for this very promising technology. At the same time, our re- sults clearly demonstrated the inadequacy of currently applied methodologies in the evaluation of specific parameters (e.g. determinants of antibiotic resistance and pathogenic bacteria) in WW.

A multi-barrier approach including advanced oxidation by Fenton (FO), air stripping (AS) and biological activated sludge (B-AS) processes was investigated as possible treatment of mature landfill leachate (MLL) in an urban wastewater treatment plant (UWTP). Three different conditions were compared to the control line (B-AS treatment of simulated urban wastewater (SWW)): MLL pre-treated with FO process and diluted to 17% with SWW; MLL pre-treated with AS and diluted to 17% with SWW; MLL pre-treated with FO, AS and diluted to 17% with SWW. Preliminary tests aimed to investigate the best operating conditions of FO for MLL (pH = 3, t = 120 min, H2O2/Fe2+ = 1, H2O2= Fe2+ = 3500 mg/L) were carried out with regard to COD removal (82%) and biodegradability (BOD5/COD = 0.32). FO and AS were very efficient to remove COD (82%) and NH3 (92%) respectively, before pre-treated MLL was mixed to SWW. The multi-barrier treatment (FO + AS + B-AS) was very efficient to remove COD (85%) and NH3 (79%). Furthermore, the absence of one of the two pre-treatments, FO or AS, adversely affected the biological process, by reducing COD (47%) and NH3 (14%) removal efficiency, respectively. The management cost analysis showed that the investigated multi barrier system is economically feasible only at low dilution ratio between FO-AS pre-treated MLL and real urban wastewater (

We carry out a mesocosms experiment to assess the impact of high-quality treated wastewater intended for agricultural reuse (HQWR) on freshwater bacteria seldom exposed to anthropogenic pollution. Effects were assessed by comparing the abundance and composition of bacterial communities as well as their resistance profile under control (source water from an unpolluted lake) and treatment conditions (source water mixed 1:1 with HQWR, with and without 5 μg L−1 of cefotaxime). We investigated the effect of the different conditions on the abundance of genes encoding resistance to β-lactams and carbapenems (blaTEM, blaCTX-M, blaOXA, and blaKPC), fluoroquinolones (qnrS), tetracyclines (tetA), sulfonamides (sul2), macrolides (ermB), arsenic and cadmium (arsB and czcA, respectively), and on the gene encoding the Class 1 integron integrase (intI1). Bacterial communities exposed to HQWR showed a significant higher abundance of tetA, arsB, czcA, and intI1 genes, whereas those exposed to Cefotaxime-amended HQWR did not. Genes conferring resistance to carbapenems, β-lactams, fluoroquinolones, and macrolides were below detection limit in all treatments. Besides, the higher availability of nutrients under treatment conditions favored bacterial growth in comparison to those exposed to control conditions. Particularly, Acinetobacter spp. and Pseudomonas spp. were significantly enriched after 22 days of treatment exposure. The presence of cefotaxime (a third generation cephalosporine) in the feeding medium caused an enrichment of bacterial communities in sequences affiliated to Acinetobacter thus suggesting that these resistant forms may possess resistance genes other than those studied here (blaCTX-M, blaOXA, and blaKPC). Although derived from a mesocosm experiment in continuous cultures, our results call attention to the need of refined regulations regarding the use of reclaimed water in agriculture since even high-quality treated wastewater may lead to undesired effects on receiving bacterial communities in terms of composition and dissemination of antibiotic resistance genes.

The fate of indigenous surface-water and wastewater antibiotic resistant bacteria in a mild slope stream simulated through a hydraulic channel was investigated in outdoor experiments. The effect of (i) natural (dark) decay, (ii) sunlight, (iii) cloudy cover, (iv) adsorption to the sediment, (v) hydraulic conditions, (vi) discharge of urban wastewater treatment plant (UWTP) effluent and (vii) bacterial species (presumptive Escherichia coli and enterococci) was evaluated. Half-life time ( T 1/2 ) of E. coli under sunlight was in the range 6.48–27.7 min (initial bacterial concentration of 10 5 CFU/mL) depending on hydraulic and sunlight conditions. E. coli inactivation was quite similar in sunny and cloudy day experiments in the early 2 hr, despite of the light intensity gradient was in the range of 15–59 W/m 2 ; but subsequently the inactivation rate decreased in the cloudy day experiment ( T 1/2 = 23.0 min) compared to sunny day ( T 1/2 = 17.4 min). The adsorption of bacterial cells to the sediment (biofilm) increased in the first hour and then was quite stable for the remaining experimental time. Finally, when the discharge of an UWTP effluent in the stream was simulated, the proportion of indigenous antibiotic resistant E. coli and enterococci was found to increase as the exposure time increased, thus showing a higher resistance to solar inactivation compared to the respective total populations.

Photo-Fenton process is among the most effective advanced oxidation processes (AOPs) in urban wastewater treatment and disinfection, but its application as tertiary treatment at full scale has not been a feasible/attractive option so far because optimum conditions are typically achieved under acidic pH. In this work a new photo Fenton like process (UV-C/H2O2/IDS-Cu) using iminodisuccinic acid (IDS)-Cu complex as catalyst, was compared to other processes (UV-C/H2O2/Cu, UV-C/H2O2/Fe, H2O2 and UV-C) in urban wastewater disinfection. Since this is the first time that IDS-Cu complex was isolated and used as catalyst, preliminary tests to evaluate the mineralization of a model compound (phenol, 25 mg L−1 initial concentration) in water by UV-C/H2O2/IDS-Cu were carried out. Almost complete mineralization of phenol (95%) was observed after 60 min treatment, being the process more effective than all other investigated AOPs (Fenton and photo-Fenton processes). This process was also proven to be more effective in the inactivation of E. coli (complete inactivation (3.5 log units) in 10 min) at natural pH (7.8 ± 0.5) in real wastewater, than the other processes investigated. Unlike of what observed for E. coli inactivation, the investigated processes only partially inactivated total bacterial population (from 18% for UV-C to 43% for UV-C/H2O2/Cu), according to flow cytometry measurements. In particular, Cu based photo-Fenton processes resulted in the higher percentage of inactivated total cells, thus being consistent with the results of E. coli inactivation. It is worthy to note that, as H2O2 was decreased, UV-C/H2O2/Cu-IDS was more effective than UV-C/H2O2/Cu process. Moreover, the formation of small and large clusters decreased in the presence of Cu and Cu-IDS complex, and process efficiency improved accordingly; these results show that Cu based AOPs can more effectively disaggregate clusters, thus making disinfection process more effective than Fe based AOPs.

The occurrence of antibiotics in urban wastewater treatment plants (UWTPs) may result in the development of antibiotic resistance and subsequently in the release of multidrug resistant bacteria (MDR) and genes into the effluent. Conventional disinfection processes are only partially effective in controlling ARB spread, so advanced oxidation processes (AOPs) have been investigated as alternative option in this work. In particular, the aim of this work was to comparatively assess the efficiency of solar disinfection and solar driven AOPs (namely H 2 O 2 /sunlight, TiO 2 /sunlight, H 2 O 2 /TiO 2 /sunlight, natural photo-Fenton) for the inactivation of a multidrug (namely ampicillin, ciprofloxacin and tetracycline) resistant E. coli strain isolated from the effluent of the biological process of an UWTP. Different concentrations of H 2 O 2 (0.588–1.470–2.205 mM), TiO 2 (50–100 mg L −1 ), H 2 O 2 /TiO 2 (0.147 mM/50 mg L −1 , 0.588 mM/100 mg L −1 ) and Fe 2+ /H 2 O 2 (0.090/0.294, 0.179/0.588, 0.358/1.176 mM) were evaluated at pilot-scale (in compound parabolic collector reactor) in real biologically treated wastewater. All investigated processes resulted in a complete inactivation (5-log decrease) of bacteria until detection limit, but the best disinfection efficiency in terms of treatment time (20 min to reach the detection limit) and required energy (0.98 kJ L −1 ) was observed for photo-Fenton at pH 4 (Fe 2+ /H 2 O 2 :0.090/0.294 mM). Antimicrobial susceptibility was tested by Kirby-Bauer disk diffusion method. Ampicillin and ciprofloxacin (to which the selected strain is resistant), cefuroxime and nitrofurantoin were chosen as tested antibiotics. None of the investigated processes affected antibiotic resistance of survived colonies.

Solar disinfection and solar-driven advanced oxidation processes (AOPs) (namely H2O2/sunlight, TiO2/sunlight, H2O2/TiO2/sunlight, solar photo-Fenton) were evaluated in the inactivation of indigenous antibiotic-resistant bacteria (ARB) in real urban wastewater. A multidrug resistant (MDR) Escherichia coli strain isolated from the effluent of the biological process of an urban wastewater treatment plant was the target ARB. The higher inactivation rates (residual density under detection limit, 2 CFU mL−1) were achieved with H2O2/TiO2/sunlight (cumulative energy per unit of volume (QUV) in the range 3–5 kJ L−1, depending on H2O2/TiO2 ratio) and H2O2/sunlight (QUV of 8 kJ L−1) processes. All investigated processes did not affect antibiotic resistance of survived colonies. Moreover, H2O2/sunlight was compared with conventional chlorination process to evaluate bacterial regrowth potential and particularly the proportion of indigenous MDR E. coli with respect to total indigenous E. coli population. Chlorination (1.0 mg Cl2 L−1) was more effective than H2O2/sunlight (50 mg H2O2 L−1) to achieve total inactivation of MDR E. coli (15 min Vs 90 min) but less effective in controlling their regrowth (24 h Vs 48 h). Interestingly, the percentage of MDR E. coli in H2O2/sunlight treated samples decreased as incubation time increased; the opposite was observed for chlorinated samples.

International audience; Salmonellosis is one of the most common causes of foodborne bacterial human disease worldwide, and the emergence of multidrug-resistant (MDR) strains of Salmonella enterica serovar Typhimurium (S. typhimurium) was associated to the incidence of invasive salmonellosis. The objective of the present work was to investigate the effects of the TiO2 photocatalysis process in terms of both bacteria inactivation and the emergence of mutants, on S. typhimurium TA102 water suspensions. The TiO2 photocatalysis was compared with a conventional disinfection process such as UV-C radiation. In spite of the faster bacterial inactivation obtained in UV-C disinfection experiments (45, 15, and 10 min for total inactivation for initial cell density 109, 108, and 107 CFU mL-1, respectively), photocatalytic disinfection (60, 30, and 15 min) was more energy efficient because of a lower energy requirement (2-20 mWs cm-2) compared to the UV-C disinfection process (5-30 mWs cm-2). During the photocatalytic experiments, the mutation frequency increased up to 1648-fold compared to background level for a 108 CFU mL-1 initial bacterial density, and mutants were inactivated after 1-10-min treatment, depending on initial bacterial cell density. In UV-C disinfection experiments, the mutation frequency increased up to 2181-fold for a 108 CFU mL-1 initial bacterial cell density, and UV-C doses in the range of 0.5-4.8 mWs cm-2 were necessary to decrease mutation frequency. In conclusion, both disinfection processes were effective in the inactivation of S. typhimurium cells, and mutants released into the environment can be avoided if cells are effectively inactivated.

The effect of TiO₂ photocatalysis on the inactivation of an antibiotic resistant Escherichia coli strain selected from an urban wastewater treatment plant (UWWTP) effluent was investigated. Different light sources including a 250 W wide spectrum lamp, a 125 W UV-A lamp and solar radiation, as well as, photocatalysts loadings (TiO₂ Degussa P25) in the range from 0.05 to 2.00 g TiO₂ L(-1) were evaluated. The higher efficiency (total bacterial inactivation after 10 min of irradiation) was observed in the absence of TiO₂ when the wastewater was irradiated using the 250 W lamp. In the presence of TiO₂ a decreasing inactivation trend was observed (99.76% and 72.22% inactivation after 10 min irradiation at 0.10 and 2.00 g TiO₂ L(-1) respectively). Under solar simulated conditions the highest inactivation efficiency (93.17%) after 10 min of irradiation was achieved at the lower photocatalyst loading (0.05 g TiO₂ L(-1)). The concept of "reactor optical thickness" was introduced to explain the rates of disinfection observed. The optimum photocatalyst loading estimated by radiation absorption-scattering modeling was found to be 0.1 g TiO₂ L(-1) for all lamps. The difference between experimental tests and modeling may be due to TiO₂ particles aggregation. Comparative kinetic tests between solar and solar simulated photocatalytic (SSP) processes using 0.05 g TiO₂ L(-1) in suspension showed a quite similar inactivation behavior up to 30 min of irradiation, but only the SSP process resulted in a total inactivation of bacteria after 60 min of exposure. Antibiotic resistant test (Kirby-Bauer) on survived colonies showed that the SSP and SP processes affected in different ways the resistance of E. coli strain to the target antibiotics.

Two solar driven Advanced Oxidation Processes (AOPs), namely sunlight/H2O2 and sunlight/peracetic acid (PAA), were investigated for the inactivation of two bacterial families (Escherichia coli and Enterococci) in real urban wastewater. Preliminary lab scale experiments were performed by using a solar simulator in order to evaluate the proper initial dose of H2O2 and PAA, respectively. According to the results achieved, 50 and 100âEUR...mgâEUR...Lâ^'1 of H2O2 and 4 and 8âEUR...mgâEUR...Lâ^'1 of PAA were chosen for the subsequent pilot scale experiments in a Compound Parabolic Collector (CPC) based reactor. The sunlight/PAA process resulted in a higher inactivation rate (3.52 log units of E. coli and 4.50 log units of Enterococci with an initial dose of 8âEUR...mg PAA Lâ^'1) compared to sunlight/H2O2 process (3.13 log units of E. coli and 2.45 log units of Enterococci with an initial dose of 100âEUR...mg H2O2 Lâ^'1) after 120âEUR...min of solar irradiation (7.42âEUR...kJâEUR...Lâ^'1 cumulative energy per unit of volume). It is noteworthy that significantly lower initial doses of PAA allowed to achieve a higher inactivation rate compared to H2O2, which makes sunlight/PAA an attractive option for wastewater disinfection in small communities.

Pharmaceuticals removal from urban wastewater by coupling conventional sand filtration with graphene adsorption reactor (GAR) was investigated. During GAR regime phase, the percentage removal of the four investigated pharmaceuticals, (namely caffeine, carbamazepine, ibuprofen and diclofenac) was higher than 95% (98.2, 97.0, 95.5 and 97.0%, respectively). In spite of the high initial concentrations of the target pharmaceuticals (10 mg/L each) and 4 months of experimentation (62 days of adsorption treatment), typical breakthrough adsorption curves were not observed. Graphene adsorption treatment effectively decreased toxicity to Daphnia magna (0–50% immobilization), but only a slight improvement in germination index (phyto-toxicity tests) was observed after GAR treatment. Finally, graphene performances were compared with conventional (granular activated carbon) adsorption process, and the best performance in the removal of pharmaceutical mixture was quite poor (62% in terms of UV absorbance) compared to GAR (96%).

Urban wastewater treatment plant (UWWTP) effluents are among the possible sources of antibiotics and antibiotic-resistant bacteria (ARB) spread into the environment. In this work, the effect of UV radiation on antibiotic-resistant Escherichia coli (E. coli) strains was compared with that of chlorination process. Under the investigated conditions, UV disinfection process resulted in a total inactivation after 60min of irradiation (1.25×10(4)μWscm(-2)) compared to 120min chlorine contact time (initial chlorine dose of 2mgL(-1)). Moreover, no change in E. coli strains' resistance to amoxicillin (AMX) (minimum inhibiting concentration (MIC)>256mgL(-1)) and sulfamethoxazole (SMZ) (MIC>1024mgL(-1)) could be observed after UV treatment, while the treatment affected resistance of the lower resistance strain to ciprofloxacin (CPX) (MIC decreased by 33% and 50% after 60 and 120min, respectively). Contrarily, chlorination process did not affect antibiotic resistance of the investigated E. coli strains. Finally, the effect of UV radiation on the mixture of three antibiotics was also investigated and photodegradation data fit quite well pseudo first order kinetic models with t1/2 values of 14, 20 and 25min for CPX, AMX and SMZ, respectively. According to these results, conventional disinfection processes may not be effective in the inactivation of ARB, and the simultaneous release of ARB and antibiotics at sub-lethal concentrations into UWWTP effluent may promote the development of resistance among bacteria in receiving water.

The effect of solar radiation on the inactivation of multidrug resistant Escherichia coli (MDR) strains selected from an urban wastewater treatment plant (UWWTP) effluent and the change of their resistance to a mixture of three antibiotics (evaluated in terms of minimum inhibit concentration (MIC)) in wastewater polluted stream were investigated. The solar photodegradation of the mixture of the three target antibiotics (amoxicillin (AMX), ciprofloxacin (CPX), and sulfamethoxazole (SMZ)) was also evaluated. Additionally, since UWWTP effluents are possible sources of antibiotics and antibiotic resistant bacteria, the disinfection by conventional chlorination process of the UWWTP effluent inoculated with MDR strains was investigated too. Solar radiation poorly affected the inactivation of the two selected antibiotic resistant E. coli strains (40 and 60% after 180 min irradiation). Moreover, solar radiation did not affect strain resistance to AMX (MIC > 256 μg/mL) and SMZ (MIC > 1024 μg/mL), but affected resistance of the lower resistance strain to CPX (MIC decreased by 33% but only after 180 min of irradiation). Chlorination of wastewater sample strongly decreased the number of the two selected antibiotic resistant E. coli strains (99.667 and 99.999%), after 60 min of contact time at 2.0 mg/L initial chlorine concentration, but the resistance of survived colonies to antibiotics was unchanged. Finally, the solar photodegradation rate of the antibiotic mixture (1 mg/L initial concentration respectively) resulted in the following order (half-life time): CPX (t 1/2 = 24 min) 1/2 = 99 min) 1/2 = 577 min). Accordingly, the risk of the development of resistance to SMZ in surface water is significantly higher compared to CPX and AMX.