María Inmaculada Polo-López

Inactivation and regrowth of multidrug resistant bacteria in urban wastewater after disinfection by solar-driven and chlorination processes.

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 CFUm L(-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.

Cross-Contamination of Residual Emerging Contaminants and Antibiotic Resistant Bacteria in Lettuce Crops and Soil Irrigated with Wastewater Treated by Sunlight/H2O2

The sunlight/H2O2 process has recently been considered as a sustainable alternative option compared to other solar driven advanced oxidation processes (AOPs) in advanced treatment of municipal wastewater (WW) to be reused for crop irrigation. Accordingly, in this study sunlight/H2O2 was used as disinfection/oxidation treatment for urban WW treatment plant effluent in a compound parabolic collector photoreactor to assess subsequent cross-contamination of lettuce and soil by contaminants of emerging concern (CECs) (determined by QuEChERS extraction and LC-QqLIT-MS/MS analysis) and antibiotic resistant (AR) bacteria after irrigation with treated WW. Three CECs (carbamazepine (CBZ), flumequine (FLU), and thiabendazole (TBZ) at 100 μg L(-1)) and two AR bacterial strains (E. coli and E. faecalis, at 10(5) CFU mL(-1)) were spiked in real WW. A detection limit (DL) of 2 CFU mL(-1) was reached after 120 min of solar exposure for AR E. coli, while AR E. faecalis was more resistant to the disinfection process (240 min to reach DL). CBZ and TBZ were poorly removed after 90 min (12% and 50%, respectively) compared to FLU (94%). Lettuce was irrigated with treated WW for 5 weeks. CBZ and TBZ were accumulated in soil up to 472 ng g(-1) and 256 ng g(-1) and up-taken by lettuce up to 109 and 18 ng g(-1), respectively, when 90 min treated WW was used for irrigation; whereas no bacteria contamination was observed when the bacterial density in treated WW was below the DL. A proper treatment time (>90 min) should be guaranteed in order to avoid the transfer of pathogens from disinfected WW to irrigated crops and soil.

Intracellular mechanisms of solar water disinfection

Solar water disinfection (SODIS) is a zero-cost intervention measure to disinfect drinking water in areas of poor access to improved water sources, used by more than 6 million people in the world. The bactericidal action of solar radiation in water has been widely proven, nevertheless the causes for this remain still unclear. Scientific literature points out that generation of reactive oxygen species (ROS) inside microorganisms promoted by solar light absorption is the main reason. For the first time, this work reports on the experimental measurement of accumulated intracellular ROS in E. coli during solar irradiation. For this experimental achievement, a modified protocol based on the fluorescent probe dichlorodihydrofluorescein diacetate (DCFH-DA), widely used for oxidative stress in eukaryotic cells, has been tested and validated for E. coli. Our results demonstrate that ROS and their accumulated oxidative damages at intracellular level are key in solar water disinfection.

Assessing the validity of solar membrane distillation for disinfection of contaminated water

AbstractTogether with desalination, reuse of wastewater is considered as a solution to mitigate the water deficit in many areas. Membrane distillation (MD) is a technology increasingly proposed for desalination and water treatment. The process is supposed to produce pure distillate, and this is what this paper evaluates. Biologically contaminated water was used in a commercial prototype of spiral-wound liquid-gap MD coupled with solar thermal energy to assess the suitability of the process for removing pathogens. Tests were done during several hours for different operating conditions. The produced distillate, the rejected concentrated solution and the feed water were monitored through time and samples were taken for microbiological analysis. Results proved the efficiency of solar MD to produce a contaminant-free distillate when Escherichia coli, Fusarium solani and Clostridium sp spores were present in the feed water. Furthermore, in the first two cases the population of biological contaminants in the con...

Conventional and New Processes for Urban Wastewater Disinfection: Effect on Emerging and Resistant Microorganisms

The continuous release of chemical and microbiological pollutants into the environment and the increasing demand for safe water call for effective water and wastewater treatment processes. In particular, the detection of resistant microorganisms (e.g. antibiotic-resistant bacteria) in the effluents of urban wastewater treatment plants disposed into surface water or reused (e.g. in crop irrigation) shows that conventional treatments and disinfection processes do not effectively control the spread of pathogens into the environment. There is a need for new and more effective disinfection processes and technologies. The aim of this chapter is to briefly describe some of the emerging and antimicrobial-resistant microorganisms detected in wastewater, as well as the conventional and new advanced available technologies for wastewater disinfection, and to evaluate and discuss their effect on these microorganisms. Moreover, regulations and policies on wastewater reuse are also critically discussed and compared.

Solar photocatalytic disinfection of agricultural pathogenic fungi ( Curvularia sp.) in real urban wastewater

The interest in developing alternative water disinfection methods that increase the access to irrigation water free of pathogens for agricultural purposes is increasing in the last decades. Advanced Oxidation Processes (AOPs) have been demonstrated to be very efficient for the abatement of several kind of pathogens in contaminated water. The purpose of the current study was to evaluate and compare the capability of several solar AOPs for the inactivation of resistant spores of agricultural fungi. Solar photoassisted H2O2, solar photo-Fenton at acid and near-neutral pH, and solar heterogeneous photocatalysis using TiO2, with and without H2O2, have been studied for the inactivation of spores of Curvularia sp., a phytopathogenic fungi worldwide found in soils and crops. Different concentrations of reagents and catalysts were evaluated at bench scale (solar vessel reactors, 200mL) and at pilot plant scale (solar Compound Parabolic Collector-CPC reactor, 20L) under natural solar radiation using distilled water (DW) and real secondary effluents (SE) from a municipal wastewater treatment plant. Inactivation order of Curvularia sp. in distilled water was determined, i.e. TiO2/H2O2/sunlight (100/50mgL-1)>H2O2/sunlight (40mgL-1)>TiO2/sunlight (100mgL-1)>photo-Fenton with 5/10mgL-1 of Fe2+/H2O2 at pH3 and near-neutral pH. For the case of SE, at near neutral pH, the most efficient solar process was H2O2/Solar (60mgL-1); nevertheless, the best Curvularia sp. inactivation rate was obtained with photo-Fenton (10/20mgL-1 of Fe2+/H2O2) requiring a previous water adicification to pH3, within 300 and 210min of solar treatment, respectively. These results show the efficiency of solar AOPs as a feasible option for the inactivation of resistant pathogens in water for crops irrigation, even in the presence of organic matter (average Dissolved Organic Carbon (DOC): 24mgL-1), and open a window for future wastewater reclamation and irrigation use.

Integration of Membrane Distillation with solar photo-Fenton for purification of water contaminated with Bacillus sp. and Clostridium sp. spores

Although Membrane Distillation (MD) has been extensively studied for desalination, it has other applications like removing all kinds of solutes from water and concentrating non-volatile substances. MD offers the possibility of producing a clean stream while concentrating valuable compounds from waste streams towards their recovery, or emerging contaminants and pathogens present in wastewater in order to facilitate their chemical elimination. This paper analyses the elimination of bacterial spores from contaminated water with MD and the role of MD in the subsequent treatment of the concentrate with photo-Fenton process. The experiments were performed at Plataforma Solar de Almería (PSA) using a plate and frame bench module with a Permeate Gap Membrane Distillation (PGMD) configuration. Tests were done for two different kinds of spores in two different water matrixes: distilled water with 3.5wt% of sea salts contaminated with spores of Bacillus subtilis (B. subtilis) and wastewater after a secondary treatment and still contaminated with Clostridium sp. spores. An analysis of the permeate was performed in all cases to determine its purity, as well as the concentrated stream and its further treatment in order to assess the benefits of using MD. Results showed a permeate free of spores in all the cases, demonstrating the viability of MD to treat biological contaminated wastewater for further use in agriculture. Moreover, the results obtained after treating the concentrate with photo-Fenton showed a shorter treatment time for the reduction of the spore concentration in the water than that when only photo-Fenton was used.

Validation and application of a multiresidue method based on liquid chromatography-tandem mass spectrometry for evaluating the plant uptake of 74 microcontaminants in crops irrigated with treated municipal wastewater

Reuse of treated wastewater for agricultural purposes can mitigate water stress in some regions where the lack of water is an extended problem. However, the environmental long-term consequences of this practice are still unknown. It is demonstrated that using reclaimed water for irrigation lead to accumulation and translocation of some microcontaminants (MCs) in soil and crops. However, so far, only a small group of contaminants has been investigated. This study aims to develop and validate a simple and efficient multiresidue method based on QuEChERs (Quick, Easy, Cheap, Effective and Rugged) extraction coupled to liquid chromatography tandem mass spectrometry (LC-MS/MS). The novelty of the study relays in the large number of MCs analyzed (74), some of them not previously investigated, in three commodities (lettuce, radish and strawberry). Optimized conditions yielded good results for the three commodities under study. Up to 84% of the compounds were recovered within a 70-120% range, with good repeatability (relative standard deviations below 20% in most cases). Method detection (MDLs) and quantification limits (MQLs) ranged from 0.01 to 2 ng/g. The proposed method was successfully applied to assess the potential uptake of MCs by lettuce and radish crops irrigated with wastewater under controlled conditions for 3 and 1.5 months, respectively. 12 compounds were detected in the crops with concentrations ranging from 0.03 to 57.6 ng/g. N-Formyl-4-aminoantipyrine (4FAA) was the most concentrated compound. The application of this method demonstrated for the first time the accumulation of 5 contaminants of emerging concern (CECs) not previously reported: 4FAA, N-Acetyl-4-aminoantipyrine (4AAA), hydrochlorothiazide, mepivacaine and venlafaxine.

Advanced microbial analysis for wastewater quality monitoring: metagenomics trend

Urban Wastewater treatment plants (UWWTPs) have played an important and fundamental role in society for water purification of contaminated human wastewaters over the last decades. Microorganisms are very important in UWWTP as their metabolic activity significantly reduces the organic load of the UWW, although there is an uncertain gap in our knowledge regarding microbial consortium structure and their activity in UWWTP operation on a large scale. On the other hand, effluents of UWWTPs have come to be a new source of fresh water to ease water scarcity in many regions of the world, especially in intensive irrigation practices. Many concerns over health risks relating to the direct reuse of this water are very well known. However, if a proper disinfection treatment is applied, these are strongly reduced as conventional methodologies have demonstrated over the last decades. In line with this, the continuous development of new devices for analytical measurement that increase the sensitivities (limit of detection) are showing that other potential risks for both environmental and human health may be associated with UWW reuse. In this work, the most important aspects related to microorganisms in UWWTPs and UWW effluents are presented. Moreover, the new developments on genetic tools for detection of microorganisms are presented, with special emphasis on metagenomic methodology. A bibliometric analysis of what has been published so far is also carried out.

Homogeneous Fenton and Photo-Fenton Disinfection of Surface and Groundwater

Polluted surface water and groundwater represent a significant human health risk as it is a vehicle for a number of diseases derived from the exposition to untreated drinking water. Historically, chlorination became a great advance on reducing the impact of many pathogens associated with polluted drinking water in developed countries, with the consequent benefits to societies growing and welfare. Nevertheless, other treatments have been investigated during the last decades with the aim of increasing their capability for treating water and overcoming the limitations of chlorination and other conventional technologies including UVC radiation and ozone. Fenton and photo-Fenton process have been demonstrated to be a good option as alternative water disinfection process during the last years. The aim of this chapter is to briefly describe the fundamentals of this process with special focus on particular aspects related to pathogens inactivation in water. Moreover, the most recent scientific contributions on the application of Fenton and photo-Fenton for water disinfection are discussed.