Wastewater Treatment Plant Discharge Research Articles

Whole UVCB Tests Can Yield Biotic and Abiotic Degradation Kinetics of Known and Unknown Constituents for an Enhanced UVCB Degradation Profile

The green transition and move towards safe and sustainable-by-design chemicals entail the need for new methods to study the biodegradability of UVCBs (substances of Unknown or Variable composition, Complex reaction products and Biological materials). Standard simulation biodegradation tests have been developed for single substances and are generally not applicable for UVCBs. The aims of this study were (1) to combine a whole UVCB biodegradation test with a sensitive constituent specific analytical technique, (2) to measure biotic and abiotic degradation of known and unknown UVCB constituents and (3) to determine the impact of a WWTP discharge on the constituent specific biodegradation in stream water. Lavender oil and black pepper oil are of significance in the perfume and cosmetics industries and served as model UVCBs. Stream water sampled upstream and downstream of a wastewater treatment plant (WWTP) discharge point was used as inoculum (i.e., naturally and wastewater adapted bacterial consortia). Tests were conducted in gastight headspace vials and automated Arrow Solid Phase Microextraction GC-MS-scan was applied on unopened vials. Peak area ratios between biotic test systems and abiotic controls were used to determine primary biodegradation kinetics, and freshly spiked analytical references to separate biotic from abiotic degradation. Biodegradation half-times were below 20 days for all known (8-12) and unknown constituents (>78) in the essential oils. Dual column GC-MS analysis produced a level 2 identification of 16 unknown lavender constituents. Biodegradation kinetics were similar in inoculum taken before and after the WWTP outlet, confirming that native stream microorganisms were competent degraders.

Monitoring (micro-)pollutants in wastewater treatment plants: Comparing discharges in wet- and dry-weather

Municipal wastewater treatment plants (WWTPs) are crucial for maintaining good quality of surface water, limiting environmental pollution. However, during wet-weather events, WWTPs become an important point-source discharge due to the activation of the bypass, which releases a mix of untreated wastewater and stormwater. This work aims to assess how the WWTP discharges (effluent and bypass) impact on the receiving surface water body during dry- and wet-weather, monitoring 78 pollutants (7 conventional pollutants, 19 heavy metals, and 52 micropollutants) in each stream (effluent during dry-weather, effluent and bypass during wet-weather), including the influent in dry-weather for comparison. The occurrence, concentration levels and variability, and environmental risk were addressed, with a specific focus on high-resolution (up to 20-min) sampling of the bypass, based on the expected relevant temporal dynamicity. A wider range of pollutants occurred in the bypass, included undetected compounds in the dry-weather influent. Besides, a greater inter-events variability in bypass concentrations was observed, but smaller intra-event variability, with only some pollutants exhibiting a distinct first-flush effect. To address the challenge of a cost-effective bypass monitoring, we explored the applicability of readily measurable water quality parameters (total suspended solids and electrical conductivity) as proxies for micropollutants. Correlations between these parameters and specific pollutant groups suggest a promising path for further investigation and broader application. The magnitude of the rain event also affected concentration levels, with event volume clearly affecting pollutants dilution. The environmental risk assessment revealed a significantly higher risk associated to bypass discharge compared to the effluent, especially for conventional pollutants, metals, and terbutryn, highlighting the urgency of improved bypass management strategies. Overall, this study highlights the contribution of wet-weather discharges from WWTPs, emphasizing the importance of high-frequency bypass monitoring to capture peak pollutant concentrations and accurately assess the environmental risk.

Sustainable control of microplastics in wastewater using the electrochemically enhanced living membrane bioreactor

Wastewater treatment plant (WWTP) discharges are major contributors to the release of microplastics (MPs) into the environment. This research work aimed to assess the performance of the novel living membrane bioreactor (LMBR), which utilizes a biological layer as a membrane filter for the removal of polyethylene (PE) MPs from wastewater. The impact of an intermittently applied low current density (0.5 mA/cm2) on the reduction of MPs in the electrochemically enhanced LMBR (e-LMBR) has also been examined. The reactors were also compared to a conventional membrane bioreactor (MBR) and an electro-MBR (e-MBR). 1H nuclear magnetic resonance spectroscopy (1H NMR) was implemented for the MPs detection and quantification in terms of mass per volume of sample.The LMBR and MBR achieved comparable mean PE MPs reduction at 95% and 96%, respectively. The MPs mass reduction in the e-LMBR slightly decreased by 2% compared to that achieved in the LMBR. This potentially indicated the partial breakdown of the MPs due to electrochemical processes. Decreasing and inconsistent NH4-N and PO4-P removal efficiencies were observed over time due to the addition of PE MPs in the MBR and LMBR. In contrast, the integration of electric field in the e-MBR and e-LMBR resulted in consistently high values of conventional contaminant removals of COD (99.72–99.77 %), NH4-N (97.96–98.67%), and PO4-P (98.44–100.00%), despite the MPs accumulation.Integrating electrochemical processes in the e-LMBR led to the development of a stable living membrane (LM) layer, as manifested in the consistently low effluent turbidity 0.49 ± 0.33 NTU. Despite the increasing MPs concentration in the mixed liquor, applying electrochemical processes reduced the fouling rates in the e-LMBR. The e-LMBR achieved comparable efficiencies in contaminant reductions as those observed in the e-MBR, while using a low-cost membrane material.

Occurrence and fate of five representative neonicotinoid insecticides across different wastewater treatment plants and the impact on receiving water bodies

Neonicotinoids (NEOs), despite their widespread use as insecticides, exhibit a notable knowledge deficit in regards to their presence in wastewater treatment plants (WWTPs) and their surrounding environments. This study delves into the presence and disposition of 5 NEOs: Thiamethoxam (THM), Clothianidin (CLO), Imidacloprid (IMD), Acetamiprid (ACE), and Thiacloprid (THA) across 3 domestic WWTPs and their receiving waters. Notably, THM, CLO, and ACE were consistently detected in all water and sludge samples, with THM emerging as the most abundant compound in both influent and effluent. Among the 3 WWTPs, WWTP 2, employing a fine bubble oxidation process, achieved the highest removal efficiency, surpassing 68%, in contrast to WWTP 1 (CAST) at 37% and WWTP 3 (A/A/O) at 7%. Biodegradation played a pivotal role in NEO removal, accounting for 36.7% and 68.2% of the total removal in WWTP 1 and WWTP 2, respectively. Surprisingly, in WWTP 3, biotransformation process inadvertently increased ACE and CLO concentrations by approximately 4.1% and 4.5%, respectively. The total NEO concentration in the receiving surface waters ranged from 72.7 to 155.5 ng/L, while sediment concentrations were significantly lower, spanning between 0.10 and 1.53 ng/g. WWTPs serve as both a removal and concentration point for NEOs, thereby significantly influencing their transportation. Additionally, the concentration of most NEOs in the receiving waters progressively increased from upstream to downstream, highlighting the substantial impact of WWTP discharges on natural water environments. This research offers valuable insights into NEO pollution surrounding WWTPs in the Pearl River Delta, ultimately aiding in pollution control and environmental protection decisions.

Pharmaceuticals in biota: The impact of wastewater treatment plant effluents on fish in Australia

Globally, pharmaceuticals and personal care products (PPCPs) are detected in surface waters receiving wastewater, yet their presence in biota, remain largely understudied. To address this, we conducted a study that measured 46 PPCPs in spot water samples and fish caught up- and downstream from wastewater treatment plants (WWTPs) in Victoria, Australia. We sampled 15 sites located along four waterways following a 3-site design: WWTP-discharge(‘hotspot’), ‘upstream’(∼2 km) and ‘downstream’(∼2 km). Spot water and fish were also sampled at reference sites >100 km from WWTP discharge (n = 3). Additionally, spot water samples were taken from WWTP effluent outflows (n = 3). From each locality, we analysed 3–12 fish (n = 131 total). In waterways, passive samplers (POCIS; ∼28d, n = 19 PPCPs) were also deployed. Individual fish (axial muscle) and water were analysed with LC-MS-MS. We found that PPCP concentrations in environmental surface water ranged from<0.02–0.97 μg/L. In WWTP effluent, the range was <0.02–1.4 μg/L. Of the 46 PPCPs analysed, 12 were detected in spot water samples and five in fish. In water, the highest concentration detected was for antidepressant venlafaxine (3 μg/L). The most frequently detected PPCPs: venlafaxine (54.9%), metoprolol (41.2%), propranolol (29.4%), carbamazepine (29.4%), caffeine (17.6%) and sulfamethoxazole (17.6%). Out of 131 fish analysed, 35 fish had detectable levels of PPCPs in the muscle tissue. The highest muscle concentrations were: venlafaxine (150 μg/kg, redfin perch), and sertraline (100 μg/kg, eel). Bioaccumulation factors ranged from 104 to 341L/kg for venlafaxine in redfins, 21-1,260L/kg for carbamazepine in redfins and eels, and 367-3,333L/kg for sertraline in eels. Based on our human health risk calculations for venlafaxine, carbamazepine, sertraline, triclosan, and caffeine, consumption of fish does not pose a significant risk to human health. Despite this, most of the detected PPCPs in surface waters exceeded 10 ng/L trigger value, which has led to further investigations by EPA. Our study highlights the need for using multiple lines of evidence for estimating risks of PPCPs.

Optimising design and operation of sewage source heat pump: techno-economic and environmental assessment

ABSTRACT Heat pump can be used to recover abundant thermal energy contained in the discharge of municipal wastewater treatment plants. While there are some design standards for common heat pump systems, the design of a sewage source heat pump (SSHP) system is still often based on a fixed heat load and neglects the interdependencies between the equipment sizing and operating parameters. To address the issue that previous design methods have not balanced investment and operational costs well from a global optimisation perspective, this work formulates the simultaneous optimisation of SSHP design and operation as a non-linear programming problem. The proposed model features the consideration of multiple working conditions caused by the impact of ambient temperature variation on the heat load of the SSHP system. The feasibility and potential benefits of the optimised SSHP system are also evaluated by incorporating techno-economic performances and environmental impact analyses into the mathematical framework. A case study is carried out to demonstrate the effectiveness of the proposed methodology. The results show that the total annual cost of the optimally designed and operated SSHP in Harbin could be 9% lower than in Beijing and 39% lower than in Shanghai, suggesting that constructing and running the SSHP system in severe cold regions with great heating demands might be more economical than in less cold regions. The CO2, SO2, and NOx emissions of the SSHP could be approximately 50% less than that of coal-fired boiler heating, and 80% less than that of direct electric heating with coal-fired electricity.

Occurrence, removal, and fate of benzothiazoles (BTHs) and benzotriazoles (BTRs) in two wastewater treatment plants in New York State, USA

Benzothiazoles (BTHs) and benzotriazoles (BTRs) are widely used in various consumer products. However, their occurrence and fate in wastewater treatment plants (WWTPs) in the United States remain poorly understood. In this study, wastewater and sludge samples were collected from two WWTPs from the Albany area of New York State (WWTPA and WWTPB) and the concentrations of three BTH derivatives (BTH, 2-OH-BTH, and 2-Me-S-BTH) and five BTR derivatives (1-OH-BTR, XTR, 4-OH-BTR, TTR, and BTR) were determined. The geometric mean (GM) concentrations of Σ(BTHs) and Σ(BTRs) in influent were in the range of 7550–8690 and 4590–6240 ng/L, whereas those in effluent were 6650–7150 and 4620–6800 ng/L, respectively. In the influent of two WWTPs, BTH, BTR, and TTR were identified as the major chemicals at respective GM concentrations of 8440, 4200, and 1280 ng/L in WWTPA, and 7300, 1180, and 2090 ng/L in WWTPB. The removal efficiencies of BTHs and BTRs following activated sludge treatment were < 80 %, and Σ(BTRs) showed a negative removal in both WWTPs. The respective mass loadings of Σ(BTHs) and Σ(BTRs) were 7240 and 5200 mg/d/1000 individuals in WWTPA, and 3530 and 2140 mg/d/1000 individuals in WWTPB. The environmental emissions of Σ(BTHs) and Σ(BTRs) from WWTP discharges were estimated at 3110–6030 and 2160–5700 mg/d/1000 individuals, respectively. Overall, BTHs and BTRs are not efficiently removed in WWTP processes. This study provides baseline information regarding the loading, fate, and discharge of BTHs and BTRs from WWTPs in the USA.

Impact of wastewater treatment and drought in an Alpine region: a multidisciplinary case study

In the context of global climate change, drought occurrence in streams of alpine origin is a recent phenomenon, whose impact is still poorly investigated. In this study, we adopted a three-disciplinary approach to investigate the response of an Alpine river (NW Italy) to severe drought conditions occurred in the year 2022. We hypothesised that the considerable loss in the water flow could exacerbate wastewater treatment plant (WWTP) discharge effects, lowering dilution capacity of the stream system and then increasing chemical/microbial pollution and altering benthic community characteristics. To assess river response to drought conditions of the considered year, the concentration of the main chemical variables, faecal indicator bacteria, pathogen presence and structural/functional organisation of benthic macroinvertebrates and diatom communities were measured monthly in the reaches located upstream and downstream of a WWTP (January–December 2022). Main environmental variables, such as flow velocity, water depth, and flow regime, were also considered. A multivariate analysis approach was then applied to emphasise correlations between selected variables and flow regime.Comparing upstream and downstream sections over the considered year, a common behaviour of chemical/microbiological parameters was observed, with generally higher concentrations of nutrients and bacterial indicators downstream of the local WWTP. Moreover, a positive correlation between water scarcity and nutrients/bacterial concentrations was revealed. The macroinvertebrate communities responded accordingly, both in terms of density and biological metric shift.Interestingly, differences between the two sections were strictly associated with hydrological conditions, with higher dissimilarities found in low-flow conditions. As the magnitude and duration of drought events are projected to increase in the years to come in different parts of Europe, this work can serve as a first building block and as a hint for future studies aimed at improving our knowledge about the consequences of these events that is pivotal for planning effective management strategies.

Factors contributing to pesticide contamination in riverine systems: The role of wastewater and landscape sources

Wastewater treatment plant (WWTP) discharges can be a source of organic contaminants, including pesticides, to rivers. An integrated model was developed for the Potomac River watershed (PRW) to determine the amount of accumulated wastewater percentage of streamflow (ACCWW) and calculate predicted environmental concentrations (PECs) for 14 pesticides in non-tidal National Hydrography Dataset Plus Version 2.1 stream segments. Predicted environmental concentrations were compared to measured environmental concentrations (MECs) from 32 stream sites that represented a range of ACCWW and land use to evaluate model performance and to assess possible non-WWTP loading sources. Statistical agreement between PECs and MECs was strongest for insecticides, followed by fungicides and herbicides. Principal component analysis utilizing optical fluorescence and ancillary water quality data identified wastewater and urban runoff sources. Pesticides that indicated relatively larger sources from WWTPs included dinotefuran, fipronil, carbendazim, thiabendazole, and prometon whereas imidacloprid, azoxystrobin, propiconazole, tebuconazole, and diuron were more related to urban runoff. In addition, PECs generally comprised a low proportion of MECs, which indicates possible dominant loading sources beyond WWTP discharges. Cumulative potential toxicity was higher for sites with greater ACCWW and/or located in developed areas. Imidacloprid, fipronil, and carbendazim accounted for the largest portion of predicted potential toxicity across sites. The chronic aquatic life toxicity benchmarks for freshwater invertebrates were exceeded for 82 % of the imidacloprid detections (n = 28) and 47 % of the fipronil detections (n = 19). These results highlight the ecological implications of pesticide contamination from WWTP discharges and also the potential legacy effects from accumulated soil and groundwater sources. Pesticide management strategies that mitigate both current and historical impacts may improve the health of aquatic ecosystems.

Occurrence and environmental risk assessment of pharmaceuticals in the Mondego river (Portugal)

In this case study pharmaceuticals were analysed in the Mondego river (Portugal) and their environmental risk assessed by means of risk quotients based on an extensive retrieval of ecotoxicological data for freshwater and saltwater species. The Mondego river crosses Coimbra, the most populated city in the Portuguese Centro Region hosting a complex of regional hospitals. Environmentally relevant and prioritised pharmaceuticals were investigated in this study and their potential hazards were evaluated by conducting a separate risk assessment for the freshwater and estuary parts of the examined river section.A target analysis approach with method detection limits down to 0.01 ng L−1 was used to determine pharmaceuticals. Twenty-one prioritised target analytes out of seven therapeutical classes (antibiotics, iodinated X-ray contrast media (ICM), analgesics, lipid reducers, antiepileptics, anticonvulsants, beta-blockers) were investigated by applying ultra-high pressure liquid chromatography coupled to a triple quadrupole mass spectrometer equipped with an electrospray ionisation source.The relative pattern of pharmaceuticals along the middle to the lower Mondego showed a quite uniform picture while an approximately 40fold increase of absolute concentrations was observed downstream of the wastewater treatment plant (WWTP) discharge of Coimbra. The most frequently measured substance groups were the ICM, represented by the non-ionic ICM iopromide (βmin: 3.03 ng L−1 - βmax: 2,810 ng L−1). Environmentally more critical substances such as carbamazepine, diclofenac, and bezafibrate, with concentrations up to and 52.6 ng L−1, 59.8 ng L−1, and 10.2 ng L−1 respectively, may potentially affect aquatic wildlife. Carbamazepine revealed elevated risk quotients (RQs >1) along the middle and lower Mondego with a maximum RQ of 53 downstream of Coimbra. Especially for saltwater species, carbamazepine and clarithromycin pose high potential risks.Especially in periods of low water discharge of the Mondego river, other pharmaceuticals as diclofenac and bezafibrate may pose additional risks downstream of the WWTP.

Occurrence and potential hazard posed by pharmaceutically active compounds in coastal waters in Cape Town, South Africa

The occurrence of 58 pharmaceutically active compounds (PhACs) in surface water at 28 coastal and five river sites, and in two stormwater flows in Cape Town, South Africa, was investigated in winter and summer. After accounting for quality assurance and control data, 33 PhACs were considered in detail. In winter, 25 PhACs were found at one or more sites and 27 in summer. Salicylic acid was the most widespread PhAC in each season. At least one PhAC was found at each site in each survey. The largest number found at a site was 22 at Lifebox23 Beach in winter and 23 at Macassar Beach and in the Black and Diep Rivers in summer. These sites are strongly directly or indirectly affected by wastewater treatment plant discharges. The range in ΣPhAC concentrations was 41 ng L−1 to 9.3 μg L−1 in winter and 109 ng L−1 to 18.9 μg L−1 in summer. The hazard posed by PhACs was estimated using Predicted No Effect Concentrations (PNEC) from several sources. Hazard Quotients (HQs) for numerous PhACs were >1, and for several even >10, including azithromycin, cimetidine, clarithromycin, erythromycin, and ibuprofen. The highest hazards were at coastal sites strongly indirectly affected by wastewater treatment plant discharges. Azithromycin, trimethoprim, and sulfamethoxazole at some sites may have promoted antibiotic resistance in bacteria, while irbesartan at some sites might have posed a hazard to fish according to the fish plasma model. The concentrations of several PhACs at some coastal sites are higher than concentrations reported in estuarine, coastal, and marine waters in other parts of the world.

Microplastics and Endocrine Disruptors in Typical Wastewater Treatment Plants in Megacity Shanghai.

The fast development of China's urbanization has led to a notable release of emerging pollutants, including microplastics (MPs) and endocrine disruptors (EDCs). Generally, these pollutants enter the coastal environment through the discharge of wastewater treatment plants (WWTPs) and finally threaten the organisms in the receiving waterbody. The study investigated the environmental behavior of MPs and EDCs in two typical WWTPs in one of the megacities in China, Shanghai. The abundance of MPs in the influent ranged from 321 to 976 items/L. Four shapes (films, fragments, fibers, and microbead) were found, while fibers and films dominated. Transparent (31-63%) and white (20-47%) MPs were more frequently observed, while polyethylene terephthalate, cellulose, and cellophane were the main polymetric materials. The size of the MPs fell between 15.8 μm and 2220 μm, and the smaller one (<500 μm) dominated. The removal efficiencies of the two WWTPs for MPs ranged from 64% to 92%, and both WWTPs performed better for large pieces of MPs (>500 μm). For EDCs, total concentrations in the influent were detected, ranging from 113 to 2780 ng/L. Two groups, including phenolic estrogens (PEs) and steroid estrogens (SEs), were detected, and PEs, especially bisphenol A (BPA), were the predominant individuals among the studied EDCs. Specifically, PEs ranged from 82.8 to 2637 ng/L, while SEs ranged from 27.3 to 143 ng/L. The removal efficiencies of the WWTPs for EDCs varied (82.8-100%) as well, possibly due to the different treatment compartments and contamination load in the influent. Seasonal variations for both MPs and EDCs were observed. Specifically, concentrations of MPs and EDCs in WWTPs influent were higher in the wet season, as well as the removal efficiency. Furthermore, there was a correlation observed between the concentrations of MPs and EDCs, suggesting that MPs and EDCs may originate from the same source and that EDCs released by MPs cannot be ignored during treatment. Finally, the study evaluated the environmental risk of the effluents. MPs led to a minor risk (Level I), while EDCs might lead to an adverse impact on algae (RQs = 0.0014-0.024) and fish (RQs = 3.4-30.2). In summary, WWTPs received considerable amounts of MPs and EDCs. Although the WWTPs removed the contaminants efficiently, the environmental risk of the effluent needs to be noted.

Microplastic contamination in urban aquatic environments: Occurrence characteristics in urban streams and stormwater runoff from urban surfaces

This study investigates microplastics in urban environments, focusing on their abundance, types, and relationships with hydrological parameters. Microplastic analyses encompassed two steps: (1) examining urban streams including discharges from a wastewater treatment plant (WWTP) during non-rainy seasons, and (2) analyzing stormwater runoff from urban surfaces for microplastic content during rainy seasons. In urban streams, WWTP discharge exhibited higher microplastic concentrations compared to other streams, indicating WWTP discharge is a dominant source of microplastic pollution. The most prevalent microplastics detected were polypropylene, polyethylene, and their copolymer, although a variety of other types were also found. Concentrations of microplastics were notably influenced by specific urban land uses, as evidenced by a strong correlation (0.95) between microplastic concentrations and areas characterized by industrial and transportation activities. During rainy seasons, microplastics followed the pattern of stormwater runoff, but the highest concentrations, significantly exceeding those in urban streams, were observed before the peak runoff. These maximum concentrations and their timing of occurrence were linked to antecedent dry days, rain intensity, and runoff rate, showing significant statistical correlations. Regardless of their sizes, a diverse range of microplastic types was identified in these conditions, with no consistent pattern across different rain events. This highlights the complex nature of urban microplastic pollution. This study reveals that aquatic ecosystems are significantly affected by two primary factors: (1) the consistent contribution of microplastics from WWTP discharges, and (2) the short-term, but severe, impacts of microplastic pollution associated with stormwater runoff. Furthermore, it suggests the development of alternative strategies to mitigate microplastic pollution in aquatic ecosystems, informed by the findings on the characteristics of microplastics in urban environments. This research underscores the urgent need for integrated urban environmental management strategies, paving the way for future studies to further explore and address the multifaceted challenges posed by microplastic pollution in aquatic ecosystems.

Potential effects of the discharge of wastewater treatment plant (WWTP) effluents in benthic communities: evidence from three distinct WWTP systems

Wastewater treatment plant (WWTP) effluents can be sources of environmental contamination. In this study, we aimed to understand whether effluents of three different WWTPs may have ecological effects in riverine recipient ecosystems. To achieve this, we assessed benthic phytobenthos and macroinvertebrate communities at three different locations relative to the effluent discharge: immediately upstream, immediately downstream and 500-m downstream the effluent discharge. Two approaches were employed: the ecological status classification as defined in the Water Framework Directive (WFD) based on biological indicators; constrained multivariate analysis to disentangle the environmental drivers (physicochemical variables and contaminants, namely metals, polycyclic aromatic hydrocarbons, pharmaceuticals, and personal care products) of ecological changes across the study sites. The results showed inconsistencies between the WFD approach and the multivariate approach, as well as between the responses of macroinvertebrates and diatoms. The WWTP effluents impacted benthic communities in a single case: macroinvertebrates were negatively affected by one of the WWTP effluents, likely by the transported pharmaceuticals (other stressors are essentially homogeneous among sites). Given the findings and the scarcity of consistent evidence on ecological impacts that WWTP effluents may have in recipient ecosystems, further research is needed towards more sustainable regulation and linked environmental protection measures.

Coupling hydrological and sanitation datasets to simulate wastewater-derived contamination in European rivers: Model development and calibration

Wastewater treatment plant (WWTP) discharges of microcontaminants negatively impact freshwater streams, underscoring the need for accurately mapping wastewater-derived contamination in water bodies across Europe (EU). In this study, we present a fast and open-source code for a microcontaminants fate and transport (MFT) model, capable of simulating contamination at a high resolution (15 arc second scale) across the EU. The model was developed using the best publicly available hydrological (HydroSHEDS) and sanitation (UWWTD) datasets and was rigorously calibrated, with a goodness of fit of 77.5% as measured by the R2. Importantly, the model demonstrated the ability to predict wastewater-derived contamination in water bodies, making it a valuable tool for planning the upgrade of WWTPs and improving the ecological condition of freshwater streams in the EU.

Salty chemical cocktails as water quality signatures: Longitudinal trends and breakpoints along different U.S. streams

Along urban streams and rivers, various processes, including road salt application, sewage leaks, and weathering of the built environment, contribute to novel chemical cocktails made up of metals, salts, nutrients, and organic matter. In order to track the impacts of urbanization and management strategies on water quality, we conducted longitudinal stream synoptic (LSS) monitoring in nine watersheds in five major metropolitan areas of the U.S. During each LSS monitoring survey, 10–53 sites were sampled along the flowpath of streams as they flowed along rural to urban gradients. Results demonstrated that major ions derived from salts (Ca2+, Mg2+, Na+, and K+) and correlated elements (e.g. Sr2+, N, Cu) formed ‘salty chemical cocktails’ that increased along rural to urban flowpaths. Salty chemical cocktails explained 46.1% of the overall variability in geochemistry among streams and showed distinct typologies, trends, and transitions along flowpaths through metropolitan regions. Multiple linear regression predicted 62.9% of the variance in the salty chemical cocktails using the six following significant drivers (p < 0.05): percent urban land, wastewater treatment plant discharge, mean annual precipitation, percent silicic residual material, percent volcanic material, and percent carbonate residual material. Mean annual precipitation and percent urban area were the most important in the regression, explaining 29.6% and 13.0% of the variance. Different pollution sources (wastewater, road salt, urban runoff) in streams were tracked downstream based on salty chemical cocktails. Streams flowing through stream-floodplain restoration projects and conservation areas with extensive riparian forest buffers did not show longitudinal increases in salty chemical cocktails, suggesting that there could be attenuation via conservation and restoration. Salinization represents a common urban water quality signature and longitudinal patterns of distinct chemical cocktails and ionic mixtures have the potential to track the sources, fate, and transport of different point and nonpoint pollution sources along streams across different regions.

Evidence of deviations between experimental and empirical mixing lengths: Multi-discharge field tests in an arid river system

Despite advances in wastewater treatment plant (WWTP) efficiencies, multiple contaminants of concern, such as microplastics, pharmaceuticals, and per- and poly-fluoroalkyl substances (PFAS) remain largely untreated near discharge points and can be highly concentrated before they are fully mixed within the receiving river. Environmental agencies enforce mixing zone permits for the temporary exceedance of water quality parameters beyond targeted control levels under the assumption that contaminants are well-mixed and diluted downstream of mixing lengths, which are typically quantified using empirical equations derived from one-dimensional transport models. Most of these equations were developed in the 1970s and have been assumed to be standard practice since then. However, their development and validation lacked the technological advances required to test them in the field and under changing flow conditions. While new monitoring techniques such as remote sensing and infrared imaging have been employed to visualize mixing lengths and test the validity of empirical equations, those methods cannot be easily repeated due to high costs or flight restrictions. We investigated the application of Lagrangian and Eulerian monitoring approaches to experimentally quantify mixing lengths downstream of a WWTP discharging into the Rio Grande near Albuquerque, New Mexico (USA). Our data spans river to WWTP discharges ranging between 2-22x, thus providing a unique dataset to test long-standing empirical equations in the field. Our results consistently show empirical equations could not describe our experimental mixing lengths. Specifically, while our experimental data revealed “bell-shaped” mixing lengths as a function of increasing river discharges, all empirical equations predicted monotonically increasing mixing lengths. Those mismatches between experimental and empirical mixing lengths are likely due to the existence of threshold processes defining mixing at different flow regimes, i.e., jet diffusion at low flows, the Coanda effect at intermediate flows, and turbulent mixing at higher flows, which are unaccounted for by the one-dimensional empirical formulas. Our results call for a review of the use of empirical mixing lengths in streams and rivers to avoid widespread exposures to emerging contaminants.

Microparticles in Wild and Caged Biota, Sediments, and Water Relative to Large Municipal Wastewater Treatment Plant Discharges.

Anthropogenically modified microparticles including microplastics are present in municipal wastewater treatment plant (WWTP) effluents; however, it is unclear whether biotic exposures are elevated downstream of these outfalls. In the fall of 2019, the present study examined whether microparticle levels in resident fish, environmental samples, and caged organisms were elevated near the Waterloo and Kitchener WWTP outfalls along the Grand River, Ontario, Canada. Wild rainbow darters (Etheostoma caeruleum) were collected from a total of 10 sites upstream and downstream of both WWTPs, along with surface water and sediment samples to assess spatial patterns over an approximately 70-km river stretch. Amphipods (Hyalella azteca), fluted-shell mussels (Lasmigona costata), and rainbow trout (Oncorhynchus mykiss) were also caged upstream and downstream of one WWTP for 14 or 28 days. Whole amphipods, fish digestive tracts, and mussel tissues (hemolymph, digestive glands, gills) were digested with potassium hydroxide, whereas environmental samples were processed using filtration and density separation. Visual identification, measurement, and chemical confirmation (subset only) of microparticles were completed. Elevated abiotic microparticles were found at several upstream reference sites as well as at one or both wastewater-impacted sites. Microparticles in amphipods, all mussel tissues, and wild fish did not show patterns indicative of increased exposures downstream of effluent discharges. In contrast, elevated microparticle counts were found in trout caged directly downstream of the outfall. Across all samples, cellulose fibers (mainly blue and clear colors) were the most common. Overall, results suggest little influence of WWTP effluents on microparticles in biota but rather a ubiquitous presence across most sites that indicates the importance of other point and nonpoint sources to this system. Environ Toxicol Chem 2024;43:1047-1061. © 2024 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Hidden threats in the plastisphere: Carbapenemase-producing Enterobacterales colonizing microplastics in river water

Carbapenem resistance poses a significant burden on healthcare systems worldwide. Microplastics (MPs) have emerged as potential contributors to antibiotic resistance spread in the environment. However, the link between MPs and carbapenem resistance remains unexplored. We investigated the prevalence of carbapenem-resistant bacteria colonizing MPs placed in a river. Three replicates of a mixture of polypropylene (PP), polyethylene (PE) and polyethylene terephthalate (PET) and of PET alone were placed both upstream and downstream a wastewater treatment plant (WWTP) discharge. Carbapenem-resistant Enterobacterales (CRE) were further characterized by phenotypic tests and whole-genome sequencing. The abundance of carbapenem-resistant bacteria on MPs increased significantly downstream the WWTP. Their prevalence was higher in the MPs mixture compared to PET alone. CRE strains colonizing MPs included Klebsiella pneumoniae (n = 3), Klebsiella quasipneumoniae (n = 3), Raoultella ornithinolytica (n = 2), Enterobacter kobei (n = 1) and Citrobacter freundii (n = 1), most (n = 8) recovered after the WWTP discharge. All strains exhibited at least one of the tested virulence traits (biofilm formation at 37 °C, haemolytic activity and siderophore production), were multi-drug resistant and carried carbapenemase-encoding genes [blaKPC-3 (n = 5), blaGES-5 (n = 2) or blaKPC-3 + blaGES-5 (n = 3)]. Uncommon phenotypes of resistance to imipenem/relebactam (n = 3) and ceftazidime/avibactam (n = 2) were observed. Two blaKPC−3-positive K. pneumoniae successfully transfer this gene trough conjugation. Genome analysis predicted all strains as human pathogens. The blaKPC−3 was associated with the Tn4401d transposon on a pBK30683-like plasmid in most of the isolates (n = 7). The blaGES-5 was mostly linked to class 3 integrons. A K. pneumoniae strain belonging to the outbreak-causing high-risk clone ST15 carried both blaKPC-3 and blaCTX-M-15. Two K. quasipneumoniae isolates carried the plasmid-mediated colistin resistance gene mcr-9. Our results underscore the role of MPs as vectors for CRE dissemination, particularly following WWTPs discharges. MPs may act as carriers, facilitating the dissemination of carbapenemase-encoding genes and potentially contributing to increased CRE incidence in the environment.

The fate of antibiotic resistance genes in wastewater containing microalgae treated by chlorination, ultra-violet, and Fenton reaction

Antibiotic resistance genes (ARGs) and bacteria (ARBs) in the effluent of wastewater treatment plants (WWTPs) are of utmost importance for the dissemination of ARGs in natural aquatic environments. Therefore, there is an urgent need for effective technologies to eliminate WWTP ARGs/ARBs and mitigate the associated risks posed by the discharged ARG in aquatic environments. To test the effective technology for eliminating ARGs/ARBs, we compared the removal of ARGs and ARBs by three different tertiary treatments, namely ultra-violet (UV) disinfection, chlorination disinfection, and Fenton oxidation. Then, the treated wastewater was co-cultured with Chlorella vulgaris (representative of aquatic biota) to investigate the fate of discharged ARGs into the aquatic environment. The results demonstrated that chlorination (at a chlorine concentration of 15 mg/L) and Fenton (at pH 2.73, with 0.005 mol/L Fe2+ and 0.0025 mol/L H2O2) treatment showed higher efficacy in ARG removal (1.8 - 4.17 logs) than UV treatment (15 min) (1.29 - 3.87 logs). Moreover, chlorine at 15 mg/L and Fenton treatment effectively suppressed ARB regeneration while UV treatment for 15 min could not. Regardless of treatments tested in this study, the input of treated wastewater to the Chlorella system increased the number of ARGs and mobile genetic elements (MGEs), indicating the potential risk of ARG dissemination associated with WWTP discharge. Among the wastewater-Chlorella co-culture systems, chlorination resulted in less of an increase in the number of ARGs and MGEs compared to Fenton and UV treatment. When comparing the wastewater systems to the co-culture systems, it was observed that Chlorella vulgaris reduced the number of ARGs and MGEs in chlorination and UV-treated wastewater; however, Chlorella vulgaris promoted ARG survival in Fenton-treated water, suggesting that aquatic microalgae might act as a barrier to ARG dissemination. Overall, chlorination treatment not only effectively removes ARGs and inhibits ARB regeneration but also shows a lower risk of ARG dissemination. Therefore, chlorination is recommended for practical application in controlling the spread of discharged ARGs from WWTP effluent in natural aquatic environments.