STP Effluents Research Articles

Evaluation of FEAST for metagenomics-based source tracking of antibiotic resistance genes.

A metagenomics-based technological framework has been proposed for evaluating the potential and utility of FEAST as an ARG profile-based source apportionment tool. To this end, a large panel of metagenomic data sets was analyzed, associating with eight source types of ARGs in environments. Totally, 1089 different ARGs were found in the 604 source metagenomes, and 396 ARG indicators were identified as the source-specific fingerprints to characterize each of the source types. With the source fingerprints, predictive performance of FEAST was checked using "leave-one-out" cross-validation strategy. Furthermore, artificial sink communities were simulated to evaluate the FEAST for source apportionment of ARGs. The prediction of FEAST showed high accuracy values (0.933±0.046) and specificity values (0.959±0.041), confirming its suitability to discriminate samples from different source types. The apportionment results reflected well the expected output of artificial communities which were generated with different ratios of source types to simulate various contamination levels. Finally, the validated FEAST was applied to track the sources of ARGs in river sediments. Results showed STP effluents were the main contributor of ARGs, with an average contribution of 76 %, followed by sludge (10 %) and aquaculture effluent (2.7 %), which were basically consistent with the actual environment in the area.

Metagenomic insights into resistome coalescence in an urban sewage treatment plant-river system

The effluents of sewage treatment plants (eSTP) are one of the critical contributors of antibiotic resistiome in rivers. Recently, community coalescence has been focused as the entire microbiome interchanges with one another. While works have reported the prevalence of antibiotic resistance genes (ARGs) in eSTP and their effects on river resistome, little research has investigated the extent of resistome coalescence in the environment. In the study, we have addressed the issue and focused on the resistome coalescence of eSTP in an urban river with a typical effluent/river coalescence model, by utilizing high-throughput sequencing (HTS)-based metagenomic assembly analysis. In all, a total of 609 ARGs were found in the eSTP-river system, conferring resistance to 30 antibiotic classes and including some emerging ARGs such as mcr-type, tetX and carbapenemase genes. Statistical analyses including linear discriminant analysis effect size (LEfSe) showed the coalescence of STP effluents increased the diversity and abundance of river resistome, indicating its low resistance to disturb the invasion of resistome community in eSTP. After coalescence in the river, the imprints of STP-derived ARGs presented a temporary increase and gradually decreased trend along the flow path. Further, an innovative fast expectation-maximization microbial source tracking (FEAST) method was used to quantitatively apportion the coalescence event, and demonstrated the contribution of eSTP on river resistome and its attenuation dynamics in the downstream. Notably, correlation-based network analysis and contig-based co-occurrence analysis showed the coalesced resistome in the downstream river co-occurred with human bacterial pathogens, mobile genetic elements and virulence factor genes, indicating potential resistome dissemination risk in the environment. This study provides more profound understanding of resistome coalescence between engineered and natural contexts, which is helpful for optimizing strategies to prevent and control resistome risk in aquatic environment.

Antibiotics in sewage treatment plants, receiving water bodies and groundwater of Chennai city and the suburb, South India: Occurrence, removal efficiencies, and risk assessment

The presence of antibiotics in the aqueous environment can alter the water microbiome, inducing antimicrobial resistance genes. Hence, the occurrence of 18 antibiotics belonging to sulfonamides, fluoroquinolones, tetracyclines, phenicols, and macrolides classes were investigated in surface water, groundwater, and sewage treatment plants in Chennai city and the suburbs. Fluoroquinolones had the maximum detection frequency in both influent and effluent samples of urban and suburban STPs, with ofloxacin and ciprofloxacin showing the highest influent concentrations. Erythromycin was the predominant antibiotic in surface water samples with an average concentration of 194.4 ng/L. All the detected antibiotic concentrations were higher in the Buckingham Canal compared to those in Adyar and Cooum rivers, possibly due to direct sewer outfalls in the canal. In groundwater samples, ciprofloxacin showed the highest levels with an average of 20.48 ng/L and the concentrations were comparable to those of surface water. The average sulfamethazine concentration in groundwater (5.2 ng/L) was found to be slightly higher than that of the surface water and much higher than the STP influent concentrations. High levels of ciprofloxacin and sulfamethazine in groundwater may be because of their high solubility and wide use. Moreover, erythromycin was completely removed after treatment in urban STPs; FQs showed relatively lesser removal efficiency (2.4–54%) in urban STPs and (8–44%) in suburban STP. Tetracyclines and phenicols were not detected in any of the samples. Ciprofloxacin and azithromycin in surface water pose a high risk in terms of estimated antibiotic resistance. This study revealed that the measured surface water concentration of antibiotics were 500 times higher for some compounds than the predicted calculated concentrations from STP effluents. Therefore, we suspect the direct sewage outlets or open drains might play an important role in contaminating surface water bodies in Chennai city.

Effects of the synthetic estrogen 17α-ethinylestradiol on Heterandria formosa populations: Does matrotrophy circumvent population collapse?

Feminization responses have been observed in some wild populations of fish living in rivers and streams, some of which have been shown to arise as a consequence of exposure to sewage treatment (STP) effluent discharges and the endocrine disrupting chemicals (EDCs) they contain which mimic or antagonize the actions of steroid hormones. The synthetic estrogen, 17α-ethinylestradiol (EE2), commonly used in oral contraceptives, is present in surface waters receiving STP effluents at concentrations ranging from non-detectable to 5 ng/L. Despite extensive evidence that EE2 negatively affects the reproductive health of fishes, relatively little is known about effects at the population level – and especially so for live-bearing fishes. To investigate the potential for such impacts, populations of the least killifish (Heterandria formosa) were exposed to 0 or 5 ng/L EE2. Exposures were started with newborn fish and continued for seven months. Chronic exposure to 5 ng/L EE2 caused significant reductions in population size, in abundances of newborns and males, and in population growth rates. The exposure also resulted in a female-biased sex ratio. However, individuals’ survival rates were not affected. This study showed that chronic exposure to 5 ng/L EE2 negatively affected population dynamics in a live-bearing fish, demonstrating that the levels of EE2 detected near STPs have the potential to impact wild populations of these fish.

Screening level mixture risk assessment of pharmaceuticals in STP effluents

We modeled the ecotoxicological risks of the pharmaceutical mixtures emitted from STP effluents into the environment. The classic mixture toxicity concept of Concentration Addition was used to calculate the total expected risk of the analytically determined mixtures, compare the expected impact of seven effluent streams and pinpoint the most sensitive group of species. The risk quotient of a single, randomly selected pharmaceutical is often more than a factor of 1000 lower than the mixture risk, clearly indicating the need to systematically analyse the overall risk of all pharmaceuticals present. The MCR, which is the ratio between the most risky compound and the total mixture risk, varies between 1.2 and 4.2, depending on the actual scenario and species group under consideration. The mixture risk quotients, based on acute data and an assessment factor of 1000, regularly exceed 1, indicating a potential risk for the environment, depending on the dilution in the recipient stream. The top 10 mixture components explain more than 95% of the mixture risk in all cases.A mixture toxicity assessment cannot go beyond the underlying single substance data. The lack of data on the chronic toxicity of most pharmaceuticals as well as the very few data available for in vivo fish toxicity has to be regarded as a major knowledge gap in this context. On the other hand, ignoring Independent Action or even using the sum of individual risk quotients as a rough approximation of Concentration Addition does not have a major impact on the final risk estimate.

CuO/SBA-15 catalyst for the catalytic ozonation of mesoxalic and oxalic acids. Water matrix effects

The depletion of mesoxalic and oxalic acids, two of the main by-products of wastewater ozone treatment, was studied in non-catalytic and catalytic ozonation using copper oxide supported on mesoporous silica SBA-15 as catalyst. The influence of the main inorganic anions present in natural and STP effluents (bicarbonates, sulphates, chlorides and phosphates) was also studied. The non-catalytic reaction rate was strongly dependent on the presence of inorganic anions and it was also almost inhibited by the presence of particulate material. Catalysed ozonation not only accelerates organic acid depletion, but was almost unaffected by the presence of these inorganic anions, or by the presence of suspended solids. The efficiency of catalytic and non-catalytic ozonation for depletion of both acids was studied in a real STP effluent. The depletion of mesoxalic acid was considerably slowed down in non-catalysed reactions, whereas under catalysed conditions it was not affected. Oxalate depletion was dominated by the formation with calcium of an insoluble salt, the precipitation equilibrium of which reversed only in the presence of a catalyst.

Occurrence and risks of antibiotics in the coastal aquatic environment of the Yellow Sea, North China

Eleven antibiotics in three different categories were investigated in two types of coastal bays (a semi-enclosed bay and an open bay) of the Yellow Sea and in fresh water (rivers and sewage treatment plants [STP] effluents) that discharged into the bays. The results revealed the presence of three predominant antibiotics: dehydration erythromycin, sulfamethoxazole and trimethoprim. These antibiotics were detected in the seawater and fresh water with concentrations of <0.23–50.4ngL−1 and <0.25–663.1ngL−1, respectively. In terms of the regional distribution of the compounds within the two types of bays, higher concentrations (<0.23–50.4ngL−1) and higher spatial variations (coefficients of variation: 98%–124%) were found in the semi-enclosed Jiaozhou Bay due to the poor water-exchange ability and to fresh-water inputs through rivers and/or STP effluents. In contrast, lower concentrations (<0.23–3.0ngL−1) and lower spatial variations (coefficients of variation: 36%–75%) were present in the open Yantai Bays due to the strong water-exchange with the open sea. The source apportionment suggested that 1) fresh-water inputs were the primary source of macrolides in the coastal water, and 2) mariculture affected the relative pollution levels of trimethoprim, sulfamethoxazole and sulfathiazole in the bays. In addition, a risk assessment based on the calculated risk quotient (RQ) showed that the dehydrated erythromycin, sulfamethoxazole and clarithromycin detected at most of the sampling sites in Jiaozhou Bay could pose high (RQ>1) risks to the most sensitive aquatic microorganisms, such as Synechococcus leopoliensis and Pseudokirchneriella subcapitata, whilst in the Yantai Bays, the compounds could pose medium risks (1≥RQ>0.1) to the same aquatic microorganisms.

Effect studies of human pharmaceuticals on Fucus vesiculosus and Gammarus spp

In two experiments, the human pharmaceutical propranolol negatively affected the physiology of two test organisms, Fucus vesiculosus and Gammarus spp. from a Baltic Sea littoral community in a concentration of 1000 μg l −1. Some effects were also observed for the lower, more ecologically relevant concentrations (10 μg l −1 and 100 μg l −1). The effects on F. vesiculosus not only increased with increasing concentration, but also with exposure time; while the effects on Gammarus spp. were more inconsistent over time. No clear effects of the pharmaceuticals diclofenac and ibuprofen were observed for any of the organisms. Physiological parameters measured were GP:R-ratio, chlorophyll fluorescence and release of coloured dissolved organic matter, respiration and ammonium excretion. Pharmaceutical substances are repeatedly detected in the Baltic Sea which is the recipient for STP effluents from more than 85 million people living in the catchment area, but the knowledge of their effects on non-target organisms is still very limited.

Intersex and reproductive impairment of wild fish exposed to multiple municipal wastewater discharges

The Grand River watershed in Ontario, Canada, receives and assimilates the outflow of 29 Municipal Wastewater Effluent (MWWE) discharges which is a mixture of domestic and industrial wastes. The purpose of this study was to investigate the cumulative impact of multiple sewage discharges on populations of wild fish. In field studies, responses of fish populations and individual fish responses in terms of growth (condition factor), reproduction (in vitro sex steroid production, gonadosomatic indices, histology [cellular development and intersex]) were assessed upstream and downstream of two municipal discharges. Fish [Greenside Darters Etheostoma blennioides and Rainbow Darters E. caeruleum] collected downstream of two municipal wastewater plants had the potential to have greater growth (longer and heavier) when compared to reference fish collections regardless of sex. Fish were not assimilating additional anthropogenic resources into energy storage (increased condition, liver somatic index). Impacts on ovarian development appeared to be minor with no differences in growth, steroid production or cellular development. Sewage exposed male fish were experiencing impairment in the capacity to produce testosterone and 11-ketotestosterone in vitro, and in cellular development (GSI, intersex). Male darters of both species collected in the upstream agricultural region demonstrated no evidence of intersex whereas our urban reference sites had incidence of intersex of up to 20%. Rates of intersex were elevated downstream of both sewage discharges studied (33% and>60%, respectively). Lower rates of intersex at the intermediate sites, and then increases downstream of second sewage discharge suggests that fish populations have to potential to recover prior to exposure to the second sewage effluent. Pre-spawning darters demonstrated dramatically higher incidence of intersex in the spring at both urban reference sites (33% and 50%, respectively), and increased more so downstream of the near-field and far-field exposure sites (60% and 100%, respectively). These findings suggest that the compounds released in STP effluents have a tendency to act on the male reproductive system. These effects may become more pronounced as projected human population growth will require the aquatic environment to assimilate an increasing amount of sewage waste.

Multi-residue analytical method for human pharmaceuticals and synthetic hormones in river water and sewage effluents by solid-phase extraction and liquid chromatography–tandem mass spectrometry

Pollutants such as human pharmaceuticals and synthetic hormones that are not covered by environmental legislation have increasingly become important emerging aquatic contaminants. This paper reports the development of a sensitive and selective multi-residue method for simultaneous determination and quantification of 23 pharmaceuticals and synthetic hormones from different therapeutic classes in water samples. Target pharmaceuticals include anti-diabetic, antihypertensive, hypolipidemic agents, β2-adrenergic receptor agonist, antihistamine, analgesic and sex hormones. The developed method is based on solid phase extraction (SPE) followed by instrumental analysis using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC–ESI-MS/MS) with 30 min total run time. River water samples (150 mL) and (sewage treatment plant) STP effluents (100 mL) adjusted to pH 2, were loaded into MCX (3 cm 3, 60 mg) cartridge and eluted with four different reagents for maximum recovery. Quantification was achieved by using eight isotopically labeled internal standards (I.S.) that effectively correct for losses during sample preparation and matrix effects during LC–ESI-MS/MS analysis. Good recoveries higher than 70% were obtained for most of target analytes in all matrices. Method detection limit (MDL) ranged from 0.2 to 281 ng/L. The developed method was applied to determine the levels of target analytes in various samples, including river water and STP effluents. Among the tested emerging pollutants, chlorothiazide was found at the highest level, with concentrations reaching up to 865 ng/L in STP effluent, and 182 ng/L in river water.

Prediction of carbamazepine in sewage treatment plant effluents and its implications for control strategies of pharmaceutical aquatic contamination

Carbamazepine (CBZ) is one of the most frequently detected pharmaceutical active compounds (PhACs) in water bodies. In this study, its concentrations in the STP effluents in 68 countries/regions are predicted with a model based on the sale volume, the water consumption, the disposal rate, the excretion rate, and the removal efficiency by the sewage system. The prediction results demonstrate a global aquatic contamination of CBZ. However, the contamination is unbalanced: most of developed economics have a concentration above 500 ng L −1. The prediction model also provides some implications on the control strategies of pharmaceutical aquatic contamination, including upgrading STPs, urine separation, waste pharmaceuticals collection, environmentally labeling pharmaceuticals, and green pharmacy. Those strategies are discussed in the context of currently available literature information.

Photolysis of β-blockers in environmental waters

Many drugs such as β-blockers have been shown to occur in aquatic environments. Even if adequate ecotoxicity data are not available, it is of primary importance to get informations about their fate in environmental waters, particularly about their photofate in sewage treatment plant effluents (STP). The main difficulties when studying pharmaceutical photochemical behaviour in environmental waters, are linked to the very low environmentally relevant concentrations (ng L −1 to μg L −1) which can generate problems in terms of analytical sensitivity. Moreover, the complexity of environmental matrices can modify micropollutants degradation kinetics. The photodegradation of β-blockers has been compared at two concentration levels (10 μg L −1 and 10 mg L −1) and in two different matrices (pure water and STP effluent). It has been shown that the concentration does not influence β-blockers degradation pathways, thus allowing the identification of degradation compounds using the 10 mg L −1 solutions. Although environmental waters speed up the degradation process, the same photoproducts were appeared in both matrices. Using LC–MS/MS, hydroxyl radical additions have been identified as an important degradation pathway for especially pindolol, propranolol and timolol, leading to several positional isomers, corresponding to mono-, di- or tri-hydroxylations. Kinetics of appearance/disappearance of these photoproducts have been studied in STP effluents.

Combining passive sampling and toxicity testing for evaluation of mixtures of polar organic chemicals in sewage treatment plant effluent

Effluent from sewage treatment plants has been associated with a range of pollutant effects. Depending on the influent composition and treatment processes the effluent may contain a myriad of different chemicals which makes monitoring very complex. In this study we aimed to monitor relatively polar organic pollutant mixtures using a combination of passive sampling techniques and a set of biochemistry based assays covering acute bacterial toxicity (Microtox), phytotoxicity (Max-I-PAM assay) and genotoxicity (umuC assay). The study showed that all of the assays were able to detect effects in the samples and allowed a comparison of the two plants as well as a comparison between the two sampling periods. Distinct improvements in water quality were observed in one of the plants as result of an upgrade to a UV disinfection system, which improved from 24x sample enrichment required to induce a 50% response in the Microtox assay to 84x, from 30x sample enrichment to induce a 50% reduction in photosynthetic yield to 125x, and the genotoxicity observed in the first sampling period was eliminated. Thus we propose that biochemical assay techniques in combination with time integrated passive sampling can substantially contribute to the monitoring of polar organic toxicants in STP effluents.

Estrogenicity of solid phase-extracted water samples from two municipal sewage treatment plant effluents and river Rhine water using the yeast estrogen screen

In the present study, the yeast estrogen screen (YES) was used to estimate the estrogenic potential of solid phase-extracted water samples from the effluents of two municipal sewage treatment plants (STPs 1 + 2) and from four lanes (left to right) of the river Rhine at Worms, Germany, i.e. downstream the STPs. Estrogenic activities of extracted water samples were expressed as 17β-estradiol equivalents (E 2-EQs). Estrogenic activity was detected in the effluents of both STPs with values of 0.242±0.038 n m (65.96±10.4 ng/l) and 0.125±0.026 nM E 2-EQs (34.1±7.18 ng/l) at STP 1 and 2, respectively. In river Rhine water, estrogenic activity was lower, however, displaying significant differences between the left and right bank of the river (0.044±0.003 n m E 2-EQs [11.97±0.7 ng/l] for lanes 1–3; 0.071±0.01 n m E 2-EQs [19.42±2.8 ng/l] for lane 4). Chemical analysis of corresponding water samples resulted in a potential estrogenic response in the YES, expressed as E 2-EQs for the known estrogens and phytoestrogens in the STP effluents with values up to 0.0662 n m E 2-EQs (18.04 ng/l). In Rhine water from lane 4, however, total estrogenic activity of steroidal estrogens was equal to 0.014 nM E 2-EQs (3.8 ng/l). Furthermore, total concentrations of flavonoids, fecal- and phytosteroids and resorcyclic lactones were about 1.2 μg/l at STP 1, 0.62 μg/l at STP 2 and 0.25 μg/l at the river Rhine, lane 4. Results indicate that estrogenic activity can clearly be measured in SPT effluents as well as in river Rhine water using the YES in combination with chemical analysis. Results from the bioassay, however, indicated a higher estrogenic potential (expressed as E 2-EQs) than that obtained by chemical analysis.

Combined in situ and in vitro assessment of the estrogenic activity of sewage and surface water samples.

In order to investigate the estrogenic activities of two municipal sewage treatment plant (STP; sites A and B) effluents and of Rhine water sampled at Worms (site C; Rhine-Neckar triangle, Germany), data from in situ experiments measuring hepatic vitellogenin expression from caged rainbow trout (Oncorhynchus mykiss) were compared with data from in vitro bioassays (yeast estrogen screen [YES], ER luciferase assay with HEK 293 cells [HEK], primary rainbow trout hepatocytes [PH]) and chemical analysis. Three sampling campaigns were carried out at each site between November 2000 and September 2001. Vitellogenin (VTG)-mRNA expression in male rainbow trout exposed for two weeks ranged from 3 +/- 5 to 619 +/- 188 and from 226 +/- 38 to 3373 +/- 1958 pg/microg total RNA at sites A and B, respectively. E2-equivalents obtained from the in vitro bioassays gave values up to 0.21 +/- 0.04 nM (57.3 +/- 10.2 ng/l, PH), 0.07 +/- 0.03 nM (20.2 +/- 6.9 ng/l; YES) and 0.008 +/- 0.002 nM (2.1 +/- 0.7 ng/l; HEK). In contrast, in one-year-old rainbow trout exposed at site C, no VTG-mRNA induction could be observed after two weeks of exposure. In vitro bioassays (YES, HEK, PH) indicated estrogenic activity at site C, which, however, was lower than at the investigated STP effluents. Chemical analysis of representative water samples from site A identified steroidal estrogens up to 5.6 ng/l 17beta-estradiol (E2), 19 ng/l estrone as well as 1.5 ng/l 17alpha-ethinylestradiol. Furthermore, the sum of fecal- and phytosteroids, resorcyclic lactones, and flavonoid concentrations were 280 (A) and 1.200 ng/l (B). In addition, site C (river Rhine) contained 3.9 ng/l E2 and 250 ng/l of fecal- and phytosteroids, respectively. Thus, STP effluents and Rhine water contain biologically relevant concentrations of estrogenic compounds, the activity of which can be detected by means of various bioassays.