Are hospital wastewater treatment plants a source of new resistant bacterial strains?

To understand which type of hospital waste may contain the highest amount of antibiotic resistant microorganisms that could be released into the environment, the bacterial strains entering and leaving a hospital wastewater treatment plant (HWTP) were identified and tested for their antibiotic susceptibility. To achieve this goal, samples were collected from three separate sites, inlet and outlet wastewater positions, and sludge generated in a septic tank. After microbiological characterization according to APHA, AWWA, and WEF protocols, the relative susceptibility of the bacterial strains to various antibiotic agents was assessed according to the Clinical and Laboratory Standards Institute guidelines, to determine whether there were higher numbers of resistant bacterial strains in the inlet wastewater sample than in the outlet wastewater and sludge samples. The results showed more antibiotic resistant bacteria in the sludge than in the inlet wastewater, and that the Enterobacteriaceae family was the predominant species in the collected samples. The most antibiotic-resistant families were found to be Streptococcacea and non-Enterobacteriaceae. Some bacterial strains were resistant to all the tested antibiotics. We conclude that the studied HWTP can be considered a source of resistant bacterial strains. It is suggested that outlet water and sludge generated in HWTPs should be monitored, and that efficient treatment to eliminate all bacteria from the different types of hospital waste released into the environment is adopted.

Degradation of cytostatics methotrexate and cytarabine through physico-chemical and advanced oxidative processes: influence of pH and combined processes on the treatment efficiency.

Environmental release of wastewater that contains cytostatic drugs can cause genotoxic impact, since these drugs act directly on the genetic material of aquatic organisms. Thus, the aim of this study was to evaluate the removal of the cytostatic drugs cytarabine (CTR) and methotrexate (MTX) using different physico-chemical methods individually (i.e. US, O3, H2O2 and UV) and combined (i.e. O3/US, US/H2O2, O3/H2O2 and O3/US/H2O2) under different pH conditions (4, 7 and 10). In the degradation tests, the efficiency of the methods applied was found to be dependent on the pH of the solution, with the degradation of CTR being better at pH 4 and MTX at pH 7 and pH 10. The US, H2O2 and US + H2O2 methods were the least efficient in degrading CTR and MTX under the pH conditions tested. The highest MTX degradation rate after 16 min of treatment at pH 7 was achieved by the O3 + H2O2 method (97.05% - C/C0 = 0.0295). For CTR, the highest degradation rate after 16 min of treatment was achieved by the O3 process (99.70% - C/C0 = 0.0030) at pH 4. In conclusion, most of the treatment methods tested for the degradation of CTR and MTX are effective. Notably, ozonolysis is an efficient process applied alone. Also, in combination with other methods (US + O3, O3 + H2O2 and O3 + H2O2 + US) it increases the degradation performance, showing a rapid removal rate of 70-94% in less than 4 min of treatment.

Beach-cast Sargassum cymosum macroalgae: biochar production and apply to adsorption of Acetaminophen in batch and fixed-bed adsorption processes.

In order to add value to the beach-cast Sargassum cymosum algae, its biomass was converted by pyrolysis process at 800°C into biochar, characterized and applied in the adsorption of Acetaminophen in batch and fixed-bed processes. Characterization by pH, Point of Zero Charge (pHPZC), Fourier-Transform Infrared Spectroscopy (FTIR), Thermogravimetric (TG), Scanning Electron Microscopy (SEM) and Surface area (BET) showed that the biochar presents properties favourable for the Acetaminophen adsorption. High surface area was obtained of 368.1 m². g-1, presenting the formation of pores, observed by SEM. The biochar showed basic characteristics (pH = 8.84 and pHPZC = 9.9), inferring an adsorption involving several different mechanisms such as dispersive interactions by π electrons, electrostatic attractions, and hydrophobic interactions. The adsorption mechanism is limited by chemisorption and governed by the formation of monolayer on the biochar surface, the Pseudo-second order kinetic and Langmuir-Freundlich isotherm model described the best behaviour of batch adsorption, with equilibrium and maximum adsorption capacity qe = 6.93 ± 0.07 mg. g-1 and qms = 12.34 ± 0.45 mg. g-1, respectively. Fixed-bed adsorption were performed varying adsorbent mass (0.3 and 0.6 g) and flow rate (2.5 and 5.0 mL. min-1), the best qy = 42.33 mg. g-1 found to adsorbent mass of 0.6 g and flow rate of 2.5 mL. min-1. Yan model described the best behaviour of the breakthrough curves data. Thus, the results provide insights into the development of adsorbents from beach-cast of Sargassum cymosum to adsorption of Acetaminophen, enhancing the use of environmental waste to obtain it.

Characterization of bacterial resistance in treated hospital wastewater.

This article seeks to characterize the bacterial profile of pediatric hospital wastewater samples collected at the outlet of a wastewater treatment plant, and to estimate their relative susceptibility to antimicrobial agents. A total of 64 strains were isolated in the wastewater samples, of which 49 were identified as belonging to different families: Enterobacteriaceae (e.g. Escherichia coli, Klebsiella sp., Citrobacter sp.) comprised 57.2% of the identified bacteria, non-Enterobacteriaceae (e.g. Aeromonas sp., Pseudomonas sp.) comprised 30.6%, and Streptococcaceae (e.g. Enterococcus sp.) comprised 12.2%. The tests of the susceptibility of the bacteria to the antimicrobial agents used in the hospital showed that 100% of the bacterial species found discharged in the hospital wastewater treatment system were resistant to one or more of the antimicrobial agents according to the criteria of the U.S. Clinical Laboratory Standards Institute/National Committee for Clinical Laboratory Standards. The antimicrobial agent tests showed that meropenem, norfloxacin, ciprofloxacin, levofloxacin, and cefepime were the most effective antimicrobials against bacteria of the Enterobacteriaceae family. For bacteria of the non-Enterobacteriaceae family, norfloxacin, ciprofloxacin, levofloxacin, and cefepime presented the most effective antimicrobial action, whereas for bacteria of the Streptococcaceae family, ampicillin, vancomycin, and gentamicin were the most effective antimicrobials. Hospital wastewater treatment plants could be considered as places of selection pressure for bacterial resistance because of the presence of antibiotic-resistant bacteria coming from sewers or created at the treatment plant.

Degradation of recalcitrant textile azo-dyes by fenton-based process followed by biochar polishing.

The use of advanced oxidative processes (AOPs) is an efficient alternative for the treatment of textile wastewaters. The aim of this study was to assess the dye removal efficiency of a Fenton-based degradation process followed by a polishing step using biochar prepared from rice husk. Six recalcitrant textile dyes - Reactive Red 195 (D1), Synolon Brown S2 (D2), Orange Remazol RGB (D3), Yellow Synozol K3 (D4), Reactive Orange (D5), and Reactive Black 5 (D6) - were treated with Fenton and photo-Fenton processes (with and without biochar polishing) under optimized conditions. The results showed a general efficiency ranking: photo-Fenton + biochar ≈ Fenton + biochar > photo-Fenton ≈ Fenton. The Fenton process was also efficient for the regeneration of the dye-saturated biochar. The photo-Fenton + biochar process achieved the following color removal percentages: D1 (98.8%), D2 (99.7%), D3 (98.9%), D4 (96.3%), D5 (94.2%) and D6 (94.8%). This process was applied to a real conventionally-treated textile wastewater and analysis showed a reduction in BOD (87.5% degradation), COD (62.5% degradation) and color (93.5% mean removal). These results reveal the possibility for the reuse of the treated water for non-potable industrial uses, for example, floor washing or the cleaning of machines and toilet areas.

Petroleum-contaminated soil: using sonolysis to improve mineralization and biodegradation potential of Fenton reaction and ozonolysis process.

The degradation efficiency of the Fenton reaction or ozonolysis (O3) to treat soil contaminated by crude petroleum was studied in association with the sonolysis process. To quantify oxidation efficiency, total organic carbon (TOC) and chemical oxygen demand (COD) were measured, while biochemical oxygen demand (BOD5) was measured to estimate biodegradation potential. TOC removal efficiency ranged from 9 to 52% to the Fenton reaction without sonolysis, and 18% and 78% with sonolysis for reagent concentrations of 1% H2O2-100 mM Fe2+ and 20% H2O2-1 mM Fe2+, respectively. For ozonolysis (after 10 and 60 min of treatment), the reduction in TOC ranged from 9 to 43% without sonolysis and 15 to 61% with sonolysis. The Fenton reaction without sonolysis increased the biodegradability in relation to the non-oxidized sample by 6% (1% H2O2-100 mM Fe2+) and 26% (20% H2O2-1 mM Fe2+), and with sonolysis the corresponding values were 13% and 42%, respectively. The biodegradation potential under ozonolysis without sonolysis increased from 0.18 (10 min of treatment) to 0.38 (30 min of treatment), and with sonolysis these values were 0.26 and 0.58, respectively. Optimization of the remediation processes is essential to determine sequential treatment order and efficiency.

Sensitivity of different parameters for selection of higher plants in urban afforestation: Exposure of Guabiroba (Campomanesia xanthocarpa O. Berg.) to diesel engine exhaust.

Urban afforestation can mitigate the effects of air pollution by acting as a sink for atmospheric emissions, but these emissions (e.g., combustion gases from diesel engines) can be a precursor of structural and physiological changes in higher plant species, which could compromise the success of afforestation projects. In this study, Guabiroba (Campomanesia xanthocarpa O. Berg.) plants were exposed in greenhouses to combustion gases emitted by a diesel engine over 120 days, with daily intermittent gas exposure. Every 30 days, leaf injury (chlorosis and necrosis), plant biomass and physiological/biochemical parameters (proteins, chlorophyll and peroxidase enzyme activity) were evaluated. The data obtained were used to construct a hierarchy of the sensitivity (and inversely, of the resistance or tolerance) of this higher plant species to the diesel oil combustion gases: peroxidase > biomass ≈ chlorophyll > protein > leaf injury. Variations in these parameters could be used for the early diagnosis of plant stress or as a marker for stress tolerance in trees. In the first case, a sensitive species could be used for the phytomonitoring of air quality and in the second case the lack of significant variations in these parameters would indicator tolerance of the plant species to air pollution. The results showed that Guabiroba, a plant native to the Atlantic forest, is sensitive to air pollution and could therefore be used for air quality monitoring, since all parameters analyzed were affected by the polluted air.