Linking the use of reclaimed water to indicators of crop stress by metabolomic and transcriptomic analyses. A tool to compare water irrigation quality.

The occurrence of contaminants of emerging concern (CECs) or heavy metals in reclaimed water used for agricultural irrigation may affect crop morphology and physiology. Here, we analyzed lettuce (Lactuca sativa) grown in outdoor lysimeters and irrigated with either tap water, used as a control, or reclaimed water: CAS-reclaimed water, an effluent from a conventional activated sludge system (CAS) followed by chlorination and sand filtration, or MBR-reclaimed water, an effluent from a membrane biological reactor (MBR). Chemical analyses identified seven CECs in the reclaimed waters, but only two of them were detected in lettuce (carbamazepine and azithromycin). Metabolomic and transcriptomic analyses revealed that irrigation with reclaimed water increased the concentrations of several crop metabolites (5-oxoproline, leucine, isoleucine, and fumarate) and of transcripts codifying for the plant stress-related genes Heat-Shock Protein 70 (HSP70) and Manganese Superoxide Dismutase (MnSOD). In both cases, MBR-water elicited the strongest response in lettuce, perhaps related to its comparatively high sodium adsorption ratio (4.5), rather than to its content in CECs or heavy metals. Our study indicates that crop metabolomic and transcriptomic profiles depend on the composition of irrigating water and that they could be used for testing the impact of water quality in agriculture.

Looking into the effects of co-contamination by micro(nano)plastics in the presence of other pollutants on irrigated edible plants.

To address water shortage challenges, treated wastewater is used to meet the demand for irrigation water in several countries worldwide. Considering the presence of pollutants in treated wastewater, its use for land irrigation might have an impact in the environment. This review article focuses on the combined effects (or potential joint toxicity) of microplastics (MPs)/nanoplastics (NPs) and other environmental contaminants present in treated wastewater on edible plants after irrigation. Initially, the concentrations of MPs/NPs in wastewater treatment plant effluents and surface waters are summarized, indicating the presence of MPs/NPs in both water matrices (i.e., wastewater after receiving treatment and lakes/rivers). Then, the results of 19 studies related to joint toxicity of MPs/NPs and co-contaminants (e.g., heavy metals and pharmaceuticals) on edible plants, are reviewed and discussed. This concurrent presence may result in several combined effects on edible plants, e.g., rapid root growth, increase in antioxidant enzymes, decrease in photosynthetic rate and increased production of ROS. These effects, as discussed in the various studies on which this review is based, can generate antagonistic or even neutral impact on plants, depending on the size of MPs/NPs and their mixing ratio with the co-contaminants. However, a combined exposure of edible plants to MPs/NPs and co-contaminants can also lead to hormetic adaptive responses. The data reviewed and discussed herein may relieve overlooked environmental impacts of treated wastewater reuse and may be useful to address challenges related to the combined effects of MPs/NPs and co-contaminants on edible plants after irrigation. The conclusions drawn in this review article are relevant to both direct (i.e., treated wastewater irrigation) and indirect (i.e., discharging treated wastewater in surface waters used for irrigation purposes) reuse, and may contribute to the implementation of the European Regulation 2020/741 on the minimum requirements for water reuse.

Multiclass target analysis of contaminants of emerging concern including transformation products, soil bioavailability assessment and retrospective screening as tools to evaluate risks associated with reclaimed water reuse.

The occurrence of 200 multiclass contaminants of emerging concern (CECs) encompassing 168 medicinal products and transformation products (TPs), 5 artificial sweeteners, 12 industrial chemicals, and 15 other compounds was investigated in influent and effluent wastewater samples collected during 7 consecutive days from 5 wastewater treatment plants (WWTPs) located in Cyprus. The methodology included a generic solid-phase extraction protocol using mixed-bed cartridges followed by Ultra-High Performance Liquid Chromatography coupled with Quadrupole-Time of Flight Mass Spectrometry (UHPLC-QTOF-MS) analysis. A total of 63 CECs were detected at least in one sample, with 52 and 55 out of the 200 compounds detected in influents and effluents, respectively. Ten (10) out of the 24 families of parent compounds and associated TPs were found in the wastewater samples (influent or effluent). 1-H-benzotriazole, carbamazepine, citalopram, lamotrigine, sucralose, tramadol, and venlafaxine (>80 % frequency of appearance in effluents) were assessed with respect to their bioavailability in soil as part of different scenarios of irrigation with reclaimed water following a qualitative approach. A high score of 12 (high probability) was predicted for 2 scenarios, a low score of 3 (rare occasions) for 2 scenarios, while the rest 28 scenarios had scores 5-8 (unlikely or limited possibility) and 9-11 (possibly). Retrospective screening was performed with the use of a target database of 2466 compounds and led to the detection of 158 additional compounds (medicinal products (65), medicinal products TPs (15), illicit drugs (7), illicit drugs TPs (3), industrial chemicals (11), plant protection products (25), plant protection products TPs (10), and various other compounds (22). This work aspires to showcase how the presence of CECs in wastewater could be investigated and assessed at WWTP level, including an expert-based methodology for assessing the soil bioavailability of CECs, with the aim to develop sustainable practices and enhance reclaimed water reuse.

A chemical, microbiological and (eco)toxicological scheme to understand the efficiency of UV-C/H2O2 oxidation on antibiotic-related microcontaminants in treated urban wastewater.

An assessment comprising chemical, microbiological and (eco)toxicological parameters of antibiotic-related microcontaminants, during the application of UV-C/H2O2 oxidation in secondary-treated urban wastewater, is presented. The process was investigated at bench scale under different oxidant doses (0-50 mg L-1) with regard to its capacity to degrade a mixture of antibiotics (i.e. ampicillin, clarithromycin, erythromycin, ofloxacin, sulfamethoxazole, tetracycline and trimethoprim) with an initial individual concentration of 100 µg L-1. The process was optimized with respect to the oxidant dose. Under the optimum conditions, the inactivation of selected bacteria and antibiotic resistant bacteria (ARB) (i.e. faecal coliforms, Enterococcus spp., Pseudomonasaeruginosa and total heterotrophs), and the reduction of the abundance of selected antibiotic resistance genes (ARGs) (e.g. blaOXA, qnrS, sul1, tetM) were investigated. Also, phytotoxicity against three plant species, ecotoxicity against Daphnia magna, genotoxicity, oxidative stress and cytotoxicity were assessed. Apart from chemical actinometry, computational fluid dynamics (CFD) modelling was applied to estimate the fluence rate. For the given wastewater quality and photoreactor type used, 40 mg L-1 H2O2 were required for the complete degradation of the studied antibiotics after 18.9 J cm-2. Total bacteria and ARB inactivation was observed at UV doses <1.5 J cm-2 with no bacterial regrowth being observed after 24 h. The abundance of most ARGs was reduced at 16 J cm-2. The process produced a final effluent with lower phytotoxicity compared to the untreated wastewater. The toxicity against Daphnia magna was shown to increase during the chemical oxidation. Although genotoxicity and oxidative stress fluctuated during the treatment, the latter led to the removal of these effects. Overall, it was made apparent from the high UV fluence required, that the particular reactor although extensively used in similar studies, it does not utilize efficiently the incident radiation and thus, seems not to be suitable for this kind of studies.

Evaluation of chemical and biological contaminants of emerging concern in treated wastewater intended for agricultural reuse.

The occurrence of chemical and biological contaminants of emerging concern (CECs) was investigated in treated wastewater intended for reuse in agriculture. An agarose hydrogel diffusion-based passive sampler was exposed to the outlet of a wastewater treatment plant (WWTP) located in Cyprus, which is equipped with membrane bioreactor (MBR). Passive samplers in triplicate were exposed according to a time-series exposure plan with maximum exposure duration of 28 days. Composite flow-proportional wastewater samples were collected in parallel with the passive sampling exposure plan and were processed by solid phase extraction using HORIZON SPE-DEX 4790 and the same sorbent material (Oasis HLB) as in the passive sampler. The analysis of passive samplers and wastewater samples enabled (i) the field-scale calibration of the passive sampler prototype by the calculation of in situ sampling rates of target substances, and (ii) the investigation of in silico predicted transformation products of the four most ecotoxicologically hazardous antibiotics (azithromycin, clarithromycin, erythromycin, ofloxacin). Additionally, the wastewater samples were subjected to the analysis of seven preselected antibiotic resistant genes (ARGs) and one mobile resistant element (int1). All extracts were analyzed for chemicals in a single batch using a highly sensitive method for pharmaceuticals, antibiotics and illicit drugs by liquid chromatography tandem MS/MS (LC-QQQ) and for various other target compounds (2316 compounds in total) by liquid chromatography high-resolution mass spectrometry (LC-HRMS). 279 CECs and all investigated ARGs (except for blaCTX-M-32) were detected, highlighting potential chemical and biological hazards related to wastewater reuse practices. 16 CECs were prioritized following ecotoxicological risk assessment, whereas sul1 and the mobile resistant element (int1) showed the highest abundance. Comprehensive monitoring efforts using novel sampling methods such as passive sampling, wide-scope target screening and molecular analysis are required to assure safe application of wastewater reuse and avoid spread and crop uptake of potentially hazardous chemicals.

Consolidated vs new advanced treatment methods for the removal of contaminants of emerging concern from urban wastewater.

Urban wastewater treatment plants (WWTPs) are among the main anthropogenic sources for the release of contaminants of emerging concern (CECs) into the environment, which can result in toxic and adverse effects on aquatic organisms and consequently on humans. Unfortunately, WWTPs are not designed to remove CECs and secondary (e.g., conventional activated sludge process, CAS) and tertiary (such as filtration and disinfection) treatments are not effective in the removal of most CECs entering WWTP. Accordingly, several advanced treatment methods have been investigated for the removal of CECs from wastewater, including consolidated (namely, activated carbon (AC) adsorption, ozonation and membranes) and new (such as advanced oxidation processes (AOPs)) processes/technologies. This review paper gathers the efforts of a group of international experts, members of the NEREUS COST Action ES1403 who for three years have been constructively discussing the state of the art and the best available technologies for the advanced treatment of urban wastewater. In particular, this work critically reviews the papers available in scientific literature on consolidated (ozonation, AC and membranes) and new advanced treatment methods (mainly AOPs) to analyse: (i) their efficiency in the removal of CECs from wastewater, (ii) advantages and drawbacks, (iii) possible obstacles to the application of AOPs, (iv) technological limitations and mid to long-term perspectives for the application of heterogeneous processes, and (v) a technical and economic comparison among the different processes/technologies.

Identification of biotransformation products of citalopram formed in activated sludge.

Citalopram (CTR) is a worldwide highly consumed antidepressant which has demonstrated incomplete removal by conventional wastewater treatment. Despite its global ubiquitous presence in different environmental compartments, little is known about its behaviour and transformation processes during wastewater treatment. The present study aims to expand the knowledge on fate and transformation of CTR during the biological treatment process. For this purpose, batch reactors were set up to assess biotic, abiotic and sorption losses of this compound. One of the main objectives of the study was the identification of the formed transformation products (TPs) by applying suspect and non-target strategies based on liquid chromatography quadrupole-time-of-flight mass spectrometry (LC-QTOF-MS). The complementary use of reversed phase liquid chromatography (RPLC) and hydrophilic interaction liquid chromatography (HILIC) for the identification of polar TPs, and the application of in-house developed quantitative structure-retention relationship (QSRR) prediction models, in addition to the comprehensive evaluation of the obtained MS/MS spectra, provided valuable information to support identification. In total, fourteen TPs were detected and thirteen of them were tentatively identified. Four compounds were confirmed (N-desmethylCTR, CTR amide, CTR carboxylic acid and 3-oxo-CTR) through the purchase of the corresponding reference standard. Probable structures based on diagnostic evidence were proposed for the additional nine TPs. Eleven TPs are reported for the first time. A transformation pathway for the biotransformation of CTR was proposed. The presence of the identified TPs was assessed in real wastewater samples through retrospective analysis, resulting in the detection of five compounds. Finally, the potential ecotoxicological risk posed by CTR and its TPs to different trophic levels of aquatic organisms was evaluated by means of risk quotients.