Wastewater Treatment Plant Effluent Discharge Research Articles

Comparative analysis of hydrodynamic flowrate sources as drivers of water quality models for nitrogenous compounds in complex ungauged South African rivers

ABSTRACT Water quality modelling is a critical tool for managing the health of river ecosystems, particularly in regions impacted by point source pollution activities. This study investigates the influence of different hydrodynamic data sources on the performance of two river water quality models, the Basic Model (BM) and the Water Quality Analysis Simulation Programme (WASP) for modelling nitrogenous compounds in a complex river system including wastewater treatment plant effluent discharges. Four diverse hydrodynamic data input types were considered. These included measured station data, altered station data, rainfall-generated flow, and the WRSM/Pitman model estimate. Findings revealed trends, analysis of variance (ANOVA), and t-test analyses consistently demonstrated significant disparities between model predictions and measured data in specific river segments, indicating a need for segment-specific modelling approaches. An increase in Root Mean Square Error (RMSE) and Mean Square Error (MSE) values in certain segments pointed to a decline in model accuracy when confronted with distinct hydrodynamic conditions. Additionally, application of four diverse hydrodynamic data input sources yielded similar performance for BM and WASP against measured data. The research findings indicated a complex interplay between river hydrodynamics and water quality modelling, resulting in a recommendation for tailored modelling strategies that account for unique characteristics of river segments.

Antibiotic, Heavy Metal, and Biocide Concentrations in a Wastewater Treatment Plant and Its Receiving Water Body Exceed PNEC Limits: Potential for Antimicrobial Resistance Selective Pressure.

Although the rise in antimicrobial resistance has been attributed mainly to the extensive and indiscriminate use of antimicrobials such as antibiotics and biocides in humans, animals and on plants, studies investigating the impact of this use on water environments in Africa are minimal. This study quantified selected antibiotics, heavy metals, and biocides in an urban wastewater treatment plant (WWTP) and its receiving water body in Kwazulu-Natal, South Africa, in the context of the predicted no-effect concentrations (PNEC) for the selection of antimicrobial resistance (AMR). Water samples were collected from the WWTP effluent discharge point and upstream and downstream from this point. Heavy metals were identified and quantified using the United States Environmental Protection Agency (US EPA) method 200.7. Biocides and antibiotic residues were determined using validated ultra-high-performance liquid chromatography with tandem mass spectrometry-based methods. The overall highest mean antibiotic, metal and biocide concentrations were observed for sulfamethoxazole (286.180 µg/L), neodymium (Nd; 27.734 mg/L), and benzalkonium chloride (BAC 12) (7.805 µg/L), respectively. In decreasing order per sampling site, the pollutant concentrations were effluent > downstream > upstream. This implies that the WWTP significantly contributed to the observed pollution in the receiving water. Furthermore, most of the pollutants measured recorded values exceeding the recommended predicted no-effect concentration (PNEC) values, suggesting that the microbes in such water environments were at risk of developing resistance due to the selection pressure exerted by these antimicrobials. Further studies are required to establish such a relationship.

Dominance of species sorting over dispersal at microgeographical scales in polluted lotic ecosystems

Global rivers, particularly those in populated urban areas, are challenged by multiple stressors such as pollution from anthropogenic activities. Dissecting the relative role of each ecological process involved in structuring biotic communities is fundamental in both theoretical and applied ecology. The ecological niche-based species sorting and stochastic dynamics-based dispersal are two major competing processes in determining community structure. Studies have reached a common realization on the environmental gradient-geographical scale relationship (EGGSR), resulting in species sorting over dispersal in determining community structure at large geographical scales where significant environmental gradients often exist. However, this relationship has been recently challenged at fine geographical scales when significant environmental gradients are formed by local anthropogenic activities. Here, we used three receiving rivers of wastewater treatment plants (WWTPs) as the promising system to test the hypothesis that species sorting plays a dominant role over dispersal in structuring zooplankton communities at microgeographical scales (∼1.2 km). After WWTP effluent discharge, we consistently detected significant environmental changes in all three receiving rivers, leading to significant variation in both community structure and taxonomic co-occurrence networks. Variation partitioning showed that environmental variables explained higher proportions of community variation than spatial ones, supporting that species sorting played a dominant role over dispersal in structuring zooplankton communities. Thus, our findings here reject EGGSR, illustrating that the effect of species sorting has been overlooked in disturbed aquatic ecosystems at fine spatial scales. More importantly, all analyses in multiple rivers here validate the “microscale species sorting” hypothesis. The validation of such hypothesis provides a novel methodology for point source pollution management by assessing environment-community interactions and functional changes of biological communities. The differed variables underlying species sorting among three rivers illustrate that ecological management should be case-specific, with the full consideration of local water quality background and pollutant composition of each point pollution source.

Tracing the fate of microplastic in wastewater treatment plant: A multi-stage analysis of treatment units and sludge

Microplastic (MP) pollution is ubiquitous in the environment presenting a global problem for both scientists and the general public. One of the major pathways of MPs entering the natural environment is through wastewater treatment plants (WWTPs). Once MPs reach the natural environment, they are posing threat to aquatic ecosystems and public health. The aim of this study is to investigate the concentration, morphology, and composition of MPs in different treatment units of a WWTP. Sampling included different points across WWTP in the water and sludge lines. Pre-treatment of the samples consists of advanced Fenton oxidation, and alkaline and enzymatic digestion followed by density separation. Once the particles were isolated, their morphology and size were studied using a stereoscopic and optical microscope followed by final confirmation with ATR-FTIR and micro-FTIR spectroscopy. Microplastic particle concentrations exhibit significant reductions as water undergoes treatment in the WWTP. For summer sampling, concentrations decreased from 351 MP/L (influent) to 35 MP/L (primary clarifier), 32 MP/L (biological reactor), and 13 MP/L (2.3 MP/L) (secondary clarifier). Similarly, winter sampling showed reductions from 403 MP/L (influent) to 159 MP/L (primary clarifier), 178 MP/L (biological reactor), and 26 MP/L (5.6 MP/L) (secondary clarifier). Removal efficiency of WWTP is high and exceeds 96%. The most abundant morphology is fibers followed by fragments and films. Polymers such as PE, synthetic cellulose, PP, PVC, PE-PP, PEEA, PA, acrylamide, and PES are widely detected in different units of WWTP. The number of MPs that are avoided from being emitted into the environment through direct water discharge was estimated to be 9.1 × 1012 MP/year. Removed MPs tend to accumulate in the sludge that is used for agricultural purposes although it should be managed as waste properly, avoiding the transition of MPs pollutants to terrestrial ecosystems adding to the number of MPs that will inevitably end up in receiving water bodies through direct WWTP effluent discharge that was set in 5.1 × 1010 MP/year in the studied WWTP.

Dynamics of antibiotic resistance markers and Escherichia coli invasion in riverine heterotrophic biofilms facing increasing heat and flow stagnation

As motivation to address environmental dissemination of antimicrobial resistance (AMR) is mounting, there is a need to characterize mechanisms by which AMR can propagate under environmental conditions. Here we investigated the effect of temperature and stagnation on the persistence of wastewater-associated antibiotic resistance markers in riverine biofilms and the invasion success of genetically-tagged Escherichia coli. Biofilms grown on glass slides incubated in-situ downstream of a wastewater treatment plant effluent discharge point were transferred to laboratory-scale flumes fed with filtered river water under potentially stressful temperature and flow conditions: recirculation flow at 20 °C, stagnation at 20 °C, and stagnation at 30 °C. After 14 days, quantitative PCR and amplicon sequencing were used to quantify bacteria, biofilms diversity, resistance markers (sul1, sul2, ermB, tetW, tetM, tetB, blaCTX-M-1, intI1) and E. coli. Resistance markers significantly decreased over time regardless of the treatment applied. Although invading E. coli were initially able to colonize the biofilms, its abundance subsequently declined. Stagnation was associated with a shift in biofilm taxonomic composition, but there was no apparent effect of flow conditions or the simulated river-pool warming (30 °C) on AMR persistence or invasion success of E. coli. Results however indicated that antibiotic resistance markers in the riverine biofilms decreased under the experimental conditions in the absence of exposure to external inputs of antibiotics and AMR.

Wastewater treatment plant effluent discharge decreases bacterial community diversity and network complexity in urbanized coastal sediment

The wastewater treatment plant (WWTP) effluent discharge affects the microorganisms in the receiving water bodies. Despite the ecological significance of microbial communities in pollutant degradation and element cycling, how the community diversity is affected by effluent remains obscure. Here, we compared the sediment bacterial communities exposed to different intensities of WWTP effluent discharge in Hangzhou Bay, China: i) a severely polluted area that receives effluent from an industrial WWTP, ii) a moderately polluted area that receives effluent from a municipal WWTP, and iii) less affected area that inner the bay. We found that the sediment bacterial diversity decreased dramatically with pollution levels of inorganic nutrients, heavy metals, and organic halogens. Microbial community assembly model analysis revealed increased environmental selection and decreased species migration rate in the severely polluted area, resulting in high phylogenetic clustering of the bacterial communities. The ecological networks were less complex in the two WWTP effluent receiving areas than in the inner bay area, as suggested by the smaller network size and lower modularity. Fewer negative network associations were detected in the severely (6.7%) and moderately (8.3%) polluted areas than in the less affected area (16.7%), indicating more collaborative inter-species behaviors are required under stressful environmental conditions. Overall, our results reveal the fundamental impacts of WWTP effluents on the ecological processes shaping coastal microbial communities and point to the potential adverse effects of diversity loss on ecosystem functions.

Spatio-seasonal patterns of the impact of wastewater treatment plant effluents on antibiotic resistance in river sediments

There is a growing concern about the risk of antibiotic resistance emergence and dissemination in the environment. Here, we evaluated the spatio-seasonal patterns of the impact of wastewater treatment plant (WWTP) effluents on antibiotic resistance in river sediments. To this purpose, sediment samples were collected in three river basins affected by WWTP effluents in wet (high-water period) and dry (low-water period) hydrological conditions at three locations: (i) upstream the WWTPs; (ii) WWTP effluent discharge points (effluent outfall); and (iii) downstream the WWTPs (500 m downriver from the effluent outfall). The absolute and relative abundances of 9 antibiotic resistance genes (ARGs), 3 mobile genetic element (MGE) genes, and 4 metal resistance genes (MRGs) were quantified in sediment samples, as well as a variety of physicochemical parameters, metal contents, and antibiotic concentrations in both sediment and water samples. In sediments, significantly higher relative abundances of most genes were observed in downstream vs. upstream sampling points. Seasonal changes (higher values in low-water vs. high-water period) were observed for both ARG absolute and relative abundances in sediment samples. Chemical data revealed the contribution of effluents from WWTPs as a source of antibiotic and metal contamination in river ecosystems. The observed positive correlations between ARG and MGE genes relative abundances point out to the role of horizontal gene transfer in antibiotic resistance dissemination. Monitoring plans that take into consideration spatio-temporal patterns must be implemented to properly assess the environmental fate of WWTP-related emerging contaminants in river ecosystems.

Application of Coagulation and Foam Concentration Method to Quantify Waterborne Pathogens in River Water Samples

One of the major challenges in detecting waterborne pathogens is the low concentration of the target bacteria in water. In this study, we applied the coagulation and foam concentration method to obtain DNA from water samples collected from upstream, near an estuary. The DNA samples were analyzed using 16S rRNA gene sequencing to clarify the microbial community shifts and to identify potentially pathogenic bacteria. Bacterial communities changed as the river flowed downstream, most likely influenced by land use and human activities such as the discharge of wastewater-treatment plant effluent. Based on the 16S rRNA gene amplicon sequencing, potentially pathogenic bacteria were detected with greater than 0.1% of their relative abundances. Among these, Yersinia ruckeri and Pseudomonas alcaligenes were widely detected in the river water. In addition, digital PCR (dPCR) was used to quantify major waterborne pathogens. Shiga toxin-producing Escherichia coli (STEC), Shigella spp., and Campylobacter jejuni were all below the limit of detection. In contrast, general E. coli, which has the beta-D-glucuronidase gene (uidA) were detected by dPCR (copies/100 mL) at similar levels to those measured using the culture-based method (as colony forming units/100 mL). These results suggest that the coagulation and foam concentration method is useful for concentrating microbes and obtaining DNA from river water samples for environmental monitoring.

Elemental composition and microbial community differences between wastewater treatment plant effluent and local natural surface water: A Zhengzhou city study

Wastewater treatment plant (WWTP) effluent is discharged into rivers as supplemental water, which may result in ecological risk. This study compares the element composition and microbial community of WWTP effluent and natural surface water (NSW) and reveals the potential ecological risk of WWTP effluent discharge. Twenty recently upgraded WWTPs and three relatively large reservoirs in Zhengzhou city, China, were selected. The contents of N, P, S, K, Ca, Mg, B, Si, Na, Fe, Mn, Co, Ni and Sn were significantly higher in WWTP effluent than in NSW, while those of Mo, V, Pb and Cd were significantly lower. There was no significant difference between WWTP effluent and NSW in terms of the element imbalance index (IMI) (representing the extent of imbalance of element proportions) relative to the class IV surface water quality standard (the control standard for most Chinese rivers). The macronutrient IMI relative to the Hoagland formula was significantly lower in WWTP effluent than in NSW, and WWTP effluent discharge could significantly lower this index in NSW; this may be an important cause of primary productivity explosion. The microbial diversity was significantly higher in WWTP effluent than in NSW. The predicted relative abundances of mobile genetic elements and oxidative-stress-tolerant phenotypes were significantly higher in WWTP effluent than in NSW, whereas the abundance of gram-negative phenotypes was significantly lower, and that of potential pathogenic phenotypes was slightly lower. The effluent from upgraded WWTPs exhibited a low risk of pathogen diffusion but a high risk of antibiotic resistance gene diffusion. The element composition and microbial community should be considered when evaluating the ecological risk of WWTP effluent discharge.

The potential role of sediments in nutrients (N, P) cycle in Marchica lagoon (Mediterranean Sea, Morocco)

The aim of this study is to present the distribution of nutrients in water and sediment of Marchica lagoon, a post-restorated lagoon located in Mediterranean Sea (NE Morocco), to estimate the impact of bottom sediments on the water quality of this lagoon, and to identify the areas more affected by eutrophication risk. Nutrient concentrations in the water column and sediments were determined in thirteen samples taken from different station of the lagoon in October 2019. Nutrient concentrations in sediment were found higher than those in surface water; very high levels of nitrogenous elements showed in all sediments samples and mainly nitrogenous components (averages of 43.58 mg of N-NH4; 0.827 mg of N-NO3; 0.054 mg of N-NO2 and 773 mg of TN per kg of dry sediment) and high levels of phosphorus with average of 620 mg P/kg of dry sediment. A strong positive correlation showed between sediment and water parameters in 0.01 and 0.05 levels. High concentrations were recorded near the nutrient-rich wastewater treatment plant effluent discharges, watershed and groundwater input. The lowest concentrations are near the new pass, this is due to the low continental inputs and the renewal of the lagoon waters by the Mediterranean Sea. Generally, the distribution of nutrient levels is influenced by continental inputs, hydrodynamics, and organic matter content in the sediment. These sediments are considered as a reservoir of nutrient pollutants, which will influence water quality by releasing sedimentary materials in the water.

Modeling the Dynamics of Mixture Toxicity and Effects of Organic Micropollutants in a Small River under Unsteady Flow Conditions.

The presence of anthropogenic organic micropollutants in rivers poses a long-term threat to surface water quality. To describe and quantify the in-stream fate of single micropollutants, the advection-dispersion-reaction (ADR) equation has been used previously. Understanding the dynamics of the mixture effects and cytotoxicity that are cumulatively caused by micropollutant mixtures along their flow path in rivers requires a new concept. Thus, we extended the ADR equation from single micropollutants to defined mixtures and then to the measured mixture effects of micropollutants extracted from the same river water samples. Effects (single and mixture) are expressed as effect units and toxic units, the inverse of effect concentrations and inhibitory concentrations, respectively, quantified using a panel of in vitro bioassays. We performed a Lagrangian sampling campaign under unsteady flow, collecting river water that was impacted by a wastewater treatment plant (WWTP) effluent. To reduce the computational time, the solution of the ADR equation was expressed by a convolution-based reactive transport approach, which was used to simulate the dynamics of the effects. The dissipation dynamics of the individual micropollutants were reproduced by the deterministic model following first-order kinetics. The dynamics of experimental mixture effects without known compositions were captured by the model ensemble obtained through Bayesian calibration. The highly fluctuating WWTP effluent discharge dominated the temporal patterns of the effect fluxes in the river. Minor inputs likely from surface runoff and pesticide diffusion might contribute to the general effect and cytotoxicity pattern but could not be confirmed by the model-based analysis of the available effect and chemical data.

Effects of Wastewater Discharge on Antibiotic Resistance Genes and Microbial Community in a Coastal Area

Wastewater treatment plants (WWTPs) are important sources of antibiotic resistance genes (ARGs) in aquatic environments. Mobile genetic elements (MGEs) and microbial communities are key factors that affect the proliferation of ARGs. To reveal the effects of WWTPs effluent discharge on the ARGs and microbial community in a coastal area, the structure and distribution of ARGs, MGEs, and microbial community in Shangyu (SY) and Jiaxing (JX) effluent receiving areas (ERAs) and the offshore area of Hangzhou Bay (HB) were investigated via high-throughput quantitative PCR and 16S rRNA high-throughput sequencing. The results showed that multidrug resistance genes were the most abundant ARGs across all the sampling sites. The diversity and abundance of ARGs and MGEs in the ERAs were much higher than those in the HB. Additionally, the diversities of the microbial community in the JX-ERA were higher than those in the SY-ERA and HB. PCoA showed that the distribution of ARGs, MGEs, and microbial communities in the ERAs and HB were significantly different, indicating that the long-term wastewater discharge could alter the distribution of ARGs, MGEs, and microbial communities in the coastal area. The co-occurrence pattern among ARGs, MGEs, and microbial communities revealed that 12 bacterial genera, such as Psychrobacter, Pseudomonas, Sulfitobacter, Pseudoalteromonas, and Bacillus, showed strong positive correlations with ARGs and MGEs. Most potential hosts carried multidrug and β-lactamase resistance genes.

Chemical characterization of riverine sediments affected by wastewater treatment plant effluent discharge

This study was aimed at assessing the contribution of wastewater treatment effluents to the contamination profile of the sediments of receiving waterways. Three wastewater treatment plants (WWTP) were addressed, encompassing different population equivalent sizes, urbanization degrees and treatment methods translating differences in expected contamination patterns. Within each WWTP system, the assessment targeted the effluent and sediment samples collected upstream and downstream the effluent discharge point; contaminants belonging to several concerning chemical classes (metals and metalloids; pesticides; pharmaceuticals and personal care products, PPCPs; and polycyclic aromatic hydrocarbons, PAHs) were quantified both in effluent and sediment samples. Clear associations between contaminants present in the effluent and corresponding sediment samples were not always verified. In fact, a noticeable difference between the number or abundance of contaminants detected in effluents and in sediments, suggesting that effluents are not always the most likely source (e.g. PAHs). However, sediment contaminants that were likely sourced by the effluents were also identified (e.g. PPCPs). Sediment analysis offers an important historical view of contamination, especially in flowing recipient ecosystems where any characterization over the water matrix is ephemeral and linking exclusively to the moment of sampling. Hence, sediments should be considered for the establishment of WWTP operational benchmarks regulating the emission of contaminants, which is currently focused mostly on effluent composition thus potentially over/underestimating the longer-term impact of effluent discharge in the recipient waterways.

Insights into the microbial community of treated wastewater, its year-round variability and impact on the receiver, using cultivation, microscopy and amplicon-based methods

Apart from chemical constituents, wastewater treatment plant (WWTP) effluents also release microorganisms that can be important to the receiving water bodies either from a sanitary point of view, or taking to the account the biogeochemical potential of the recipients. However, little is known about the treated wastewater microbial community, its composition, seasonal changes, functions and fate in the waters of the receiver. Thus, this study presents a synergistic approach coupling new and traditional methods: analytical chemistry, classical microbiology (cultivation- and microscopy-based methods), as well as Next Generation Sequencing and a quantitative real-time polymerase chain reaction (qPCR). The results show that in terms of bacterial community composition, treated wastewater differed from the environmental samples, irrespectively if they were related or unrelated to the WWTP effluent discharge. The canonical correspondence analysis (CCA) taking into account chemical parameters and taxonomical biodiversity indirectly confirmed the seasonal deterioration of the treated wastewater quality as a result of temperature-driven change of activated sludge community structure and biomass washout (observed also by DAPI staining). Despite seasonal fluctuations of total suspended solids and inter-related parameters (such as COD, BOD, TN, TP), the treated wastewater quality remained within current discharge limits. It was due to treatment processes intensively adjusted by WWTP operators, particularly those necessary to maintain an appropriate rate of autotrophic processes of nitrification and to support biological phosphorus removal. This can explain the observed microbiome composition similarity among WWTP effluents at high taxonomic levels. Obtained data also suggest that besides wastewater treatment efficiency, WWTP effluents are still sources of both human-related microorganisms as well as bacteria equipped in genes involved in N-cycling. Their potential of participation in nutrients cycling in the receivers is widely unknown and require critical attention and better understanding.

Distribution and characteristics of wastewater treatment plants within the global river network

Abstract. The main objective of wastewater treatment plants (WWTPs) is to remove pathogens, nutrients, organics, and other pollutants from wastewater. After these contaminants are partially or fully removed through physical, biological, and/or chemical processes, the treated effluents are discharged into receiving waterbodies. However, since WWTPs cannot remove all contaminants, especially those of emerging concern, they inevitably represent concentrated point sources of residual contaminant loads into surface waters. To understand the severity and extent of the impact of treated-wastewater discharges from such facilities into rivers and lakes, as well as to identify opportunities of improved management, detailed information about WWTPs is required, including (1) their explicit geospatial locations to identify the waterbodies affected and (2) individual plant characteristics such as the population served, flow rate of effluents, and level of treatment of processed wastewater. These characteristics are especially important for contaminant fate models that are designed to assess the distribution of substances that are not typically included in environmental monitoring programs. Although there are several regional datasets that provide information on WWTP locations and characteristics, data are still lacking at a global scale, especially in developing countries. Here we introduce a spatially explicit global database, termed HydroWASTE, containing 58 502 WWTPs and their characteristics. This database was developed by combining national and regional datasets with auxiliary information to derive or complete missing WWTP characteristics, including the number of people served. A high-resolution river network with streamflow estimates was used to georeference WWTP outfall locations and calculate each plant's dilution factor (i.e., the ratio of the natural discharge of the receiving waterbody to the WWTP effluent discharge). The utility of this information was demonstrated in an assessment of the distribution of treated wastewater at a global scale. Results show that 1 200 000 km of the global river network receives wastewater input from upstream WWTPs, of which more than 90 000 km is downstream of WWTPs that offer only primary treatment. Wastewater ratios originating from WWTPs exceed 10 % in over 72 000 km of rivers, mostly in areas of high population densities in Europe, the USA, China, India, and South Africa. In addition, 2533 plants show a dilution factor of less than 10, which represents a common threshold for environmental concern. HydroWASTE can be accessed at https://doi.org/10.6084/m9.figshare.14847786.v1 (Ehalt Macedo et al., 2021).

Quantitative Determination and Environmental Risk Assessment of 102 Chemicals of Emerging Concern in Wastewater-Impacted Rivers Using Rapid Direct-Injection Liquid Chromatography-Tandem Mass Spectrometry.

The rapid source identification and environmental risk assessment (ERA) of hundreds of chemicals of emerging concern (CECs) in river water represent a significant analytical challenge. Herein, a potential solution involving a rapid direct-injection liquid chromatography–tandem mass spectrometry method for the quantitative determination of 102 CECs (151 qualitatively) in river water is presented and applied across six rivers in Germany and Switzerland at high spatial resolution. The method required an injection volume of only 10 µL of filtered sample, with a runtime of 5.5 min including re-equilibration with >10 datapoints per peak per transition (mostly 2 per compound), and 36 stable isotope-labelled standards. Performance was excellent from the low ng/L to µg/L concentration level, with 260 injections possible in any 24 h period. The method was applied in three separate campaigns focusing on the ERA of rivers impacted by wastewater effluent discharges (1 urban area in the Basel city region with 4 rivers, as well as 1 semi-rural and 1 rural area, each focusing on 1 river). Between 25 and 40 compounds were quantified directly in each campaign, and in all cases small tributary rivers showed higher CEC concentrations (e.g., up to ~4000 ng/L in total in the R. Schwarzach, Bavaria, Germany). The source of selected CECs could also be identified and differentiated from other sources at pre- and post- wastewater treatment plant effluent discharge points, as well as the effect of dilution downstream, which occurred over very short distances in all cases. Lastly, ERA for 41 CECs was performed at specific impacted sites, with risk quotients (RQs) at 1 or more sites estimated as high risk (RQ > 10) for 1 pharmaceutical (diclofenac), medium risk (RQ of 1–10) for 3 CECs (carbamazepine, venlafaxine, and sulfamethoxazole), and low risk (RQ = 0.1–1.0) for 7 CECs (i.e., RQ > 0.1 for 11 CECs in total). The application of high-throughput methods like this could enable a better understanding of the risks of CECs, especially in low flow/volume tributary rivers at scale and with high resolution.

Effects-based monitoring of bioactive compounds associated with municipal wastewater treatment plant effluent discharge to the South Platte River, Colorado, USA

Previous studies have detected numerous organic contaminants and in vitro bioactivities in surface water from the South Platte River near Denver, Colorado, USA. To evaluate the temporal and spatial distribution of selected contaminants of emerging concern, water samples were collected throughout 2018 and 2019 at 11 sites within the S. Platte River and surrounding tributaries with varying proximities to a major wastewater treatment plant (WWTP). Water samples were analyzed for pharmaceuticals, pesticides, steroid hormones, and wastewater indicators and screened for in vitro biological activities. Multiplexed, in vitro assays that simultaneously screen for agonistic activity against 24 human nuclear receptors detected estrogen receptor (ER), peroxisome proliferator activated receptor-gamma (PPARγ), and glucocorticoid receptor (GR) bioactivities in water samples near the WWTP outflow. Targeted in vitro bioassays assessing ER, GR, and PPARγ agonism corroborated bioactivities for ER (up to 55 ± 9.7 ng/L 17β-estradiol equivalents) and GR (up to 156 ± 28 ng/L dexamethasone equivalents), while PPARγ activity was not confirmed. To evaluate the potential in vivo significance of the bioactive contaminants, sexually-mature fathead minnows were caged at six locations upstream and downstream of the WWTP for 5 days after which targeted gene expression analyses were performed. Significant up-regulation of male hepatic vitellogenin was observed at sites with corresponding in vitro ER activity. No site-related differences in GR-related transcript abundance were detected in female adipose or male livers, suggesting observed environmental concentrations of GR-active contaminants do not induce a detectable in vivo response. In line with the lack of detectable targeted in vitro PPARɣ activity, there were no significant effects on PPARɣ-related gene expression. Although the chemicals responsible for GR and PPAR-mediated bioactivities are unknown, results from the present study provide insights into the significance (or lack thereof) of these bioactivities relative to short-term in situ fish exposures.

Corbicula fluminea rapidly accumulate pharmaceuticals from an effluent dependent urban stream

Freshwater bivalve populations are stressed by watershed development at the global scale. Though pharmaceuticals released from wastewater treatment plant effluent discharges are increasingly reported to bioaccumulate in fish, an understanding of bioaccumulation in bivalves is less defined. In the present study, we examined accumulation of 12 target pharmaceuticals in C. fluminea during a 42 day in situ study in Pecan Creek, an effluent dependent wadeable stream in north central Texas, USA. Caged clams were placed at increasing distances (5 m, 643 m, 1762 m) downstream from a municipal effluent discharge and then subsampled on study days 7, 14, 28 and 42. Acetaminophen, caffeine, carbamazepine, diltiazem, diphenhydramine, fluoxetine, norfluoxetine, sertraline, desmethylsertraline, and methylphenidate were identified in C. fluminea whole body tissue homogenates via isotope dilution liquid chromatography-tandem mass spectrometry. Tissue concentrations ranged from low μg/kg (methylphenidate) to 341 μg/kg (sertraline). By study day 7, rapid and apparent pseudo-steady state accumulation of study compounds was observed in clams; this observation continued throughout the 42 d study. Notably, elevated bioaccumulation factors (L/kg) for sertraline were observed between 3361 and 6845, which highlights the importance of developing predictive bioaccumulation models for ionizable contaminants with bivalves. Future research is also necessary to understand different routes of exposure and elimination kinetics for pharmaceutical accumulation in bivalves.

Prevalence of antibiotics and antibiotic resistance genes in a wastewater effluent-receiving river in the Netherlands

Antibiotics are being used intensively for humans and livestock worldwide and have led to the presence of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment. Wastewater treatment plants (WWTPs) have been identified as a point source for ARB&Gs, and water catchments consequently are potential receptors of ARB&Gs. The objective of this study was to investigate the occurrence of antibiotics (macrolides, sulfonamides, tetracyclines), ARGs (ermB, sul1, sul2, tetW), and class 1 integron (targeting the integrase gene), in a Dutch river that receives wastewater treatment plant effluent. Sediment and water samples were collected during one year along the river. The WWTP significantly increased the amounts of antibiotics and ARGs in the river as compared to the upstream samples, of which the antibiotics decreased once they entered the river. ARGs were persistent in the water and sediment from the WWTP effluent discharge point until 20 km downstream. This study provides insight in the prevalence of antibiotics and ARGs in a wastewater effluent-receiving river system in the Netherlands. Even though human antibiotic usage is low in the Netherlands, antibiotics, residues of antibiotics, and ARGs are detected in the river surface water-sediment system, which shows that a river has the potential to act as a reservoir of ARGs.

Occurrence and fate of antibiotics in a wastewater treatment plant and their biological effects on receiving waters in Guizhou

Abstract Wastewater treatment plants (WWTPs) are not designed for the removal of antibiotics. Thus, several studies have been conducted to evaluate the fate of antibiotics in wastewater treatment processes. However, most of these investigations did not consider the antibiotic contamination in the receiving waters. This study investigated the occurrence and fate of antibiotics in a wastewater treatment plant and the ecological risks posed by surface water receiving the effluent discharge. The results indicated that the levels of 18 antibiotics in the influent ranged from 37.21 ng L−1 to 2935.40 ng L−1, and sulfamethizole (SMZ) was the major component among the 18 antibiotics; SMZ occurred most frequently and at the highest concentrations. Mass balance analysis was performed to explore the mechanisms of antibiotic removal, and the findings indicated that biotic and abiotic degradation are the major removal mechanisms; however, removal of quinolones is primarily ascribed to sludge adsorption. Because activated sludge consists of negatively charged colloidal particles, it is more inclined to adsorb quinolones, which contain positively charged nitrogen atoms. The resulting loading of antibiotics from WWTP effluent discharge into the receiving water of the Yangjie River may result in their uptake by aquatic organisms and thus poses a risk to human health.