Influence of seasonality and vegetation on the attenuation of emerging contaminants in wastewater effluent-dominated streams. A preliminary study

Occurrence of antibiotics in hospital wastewater effluents discharged into the Niger River in Bamako, Mali. Risk assessment and solutions

Hospital wastewater effluents are a significant source of antibiotics (ABs) contamination in aquatic environments, contributing to antimicrobial resistance (AMR). This study examines 30 pharmaceutical compounds, including 22 ABs, in wastewater effluents from four hospitals in Bamako, Mali, at exit points (Po) and discharge sites (Pf) into the Niger River. The ABs belong to nine classes, mainly fluoroquinolones, macrolides, and sulfonamides. While half of the ABs were undetected, concentrations of detected ABs ranged from 0.1 to nearly 40 μg/L. Acetyl-sulfamethoxazole (ASMX) and ciprofloxacin (CIP) recorded the highest concentrations at 38.9 ± 25.7 μg/L and 32.0 ± 4.3 μg/L, respectively. Low concentrations (<1 μg/L) were observed for azithromycin, clarithromycin, and sulfadiazine. Significant variations in concentrations between Po and Pf were noted, with some ABs, like ASMX, achieving 100% abatement due to natural attenuation, while others, such as CIP and lincomycin, showed increases of up to 102% and 400%, respectively, possibly due to downstream accumulation or degradation of conjugates. Ecotoxicological and the potential microbial risk selection values revealed high risks (RQ > 1) at all sites although three of the hospitals reduced risks by over 50% for most of them. These findings underscore the need for effective wastewater treatment systems to mitigate ABs contamination. The study also provides critical baseline data and advocates for cost-effective, nature-based solutions like constructed wetlands and regulatory measures to reduce antibiotic pollution and curb risks for AMR proliferation in the Niger River.

Impact of riverbed renaturalization on the attenuation of antibiotics and antimicrobial resistance in wastewater effluent-dominated streams

Mediterranean streams contain substantial proportions of wastewater treatment plant effluent, occasionally constituting the entire water flow. Here, we analysed the seasonal occurrence of 23 antibiotics (AB) and antimicrobial resistance (AMR) by tracking 3 marker genes and bacterial community dynamics in two wastewater effluent-dominated streams. One stream was renaturalized with meanders and vegetation, while the other was linear and had a low vegetation density. The concentration of ABs in the effluents ranged from 33 to 1313 ng·L-1 during summer and 4 to 2337 ng·L-1 during winter. The attenuation of ABs 3.5 km downstream varied depending on the compound, ranging from 42 to 88%. The half-lives of ABs obtained for the streams were 0.2-4.1 h in summer and 0.6-12.6 h in winter. Most ABs had a half-life of <5 h, except sulfamethoxazole, acetyl-sulfamethoxazole, and trimethoprim. The vegetated stream exhibited a higher attenuation of ABs than the unaltered stream (88% vs. 67% on average), while also showing lower half-life values (on average 1.3 vs. 3.8 h). The bacterial community profiles in both streams were typical of effluents, with greater longitudinal dynamics in the vegetated stream during summer than in the other samplings. Similarly, AMR indicator genes decreased most in the vegetated stream during summer (0.8-1.1 log units). The ecotoxicological risk and the potential microbial risk selection values downstream at 3.5 km were reduced by > 45%. Overall, the results suggest that vegetation and meanders play an important role in the in-stream attenuation of ABs and AMRs.

Holistic assessment of chemical and biological pollutants in a Mediterranean wastewater effluent-dominated stream: Interactions and ecological impacts

The discharge of treated wastewater from wastewater treatment plants (WWTPs) into river systems is a significant source of pollution, introducing a range of chemical and biological pollutants that impact the chemical and ecological quality status of rivers. This study evaluates the effect of a secondary treated wastewater effluent on the Onyar River, in the northeast of Spain. Water and biofilm samples were collected at one upstream and four downstream sampling points (up to 2.8 km from the discharge point) across four seasons. A wide array of pollutants, including metals, pharmaceuticals, microplastics (MPs), per- and polyfluoroalkyl substances (PFAS), antibiotic resistance genes (ARGs), among other emerging pollutants, were detected downstream, with significant differences between upstream and downstream concentrations. Our results show that WWTP discharge also altered biofilm microbiome composition and ARGs presence, being these changes distinguishable from seasonal variations. Nevertheless, a partial recovery further downstream (525 m) was observed for biofilm microbiome and ARGs composition. These findings highlight the value of microbiome analysis in assessing wastewater impacts on river ecosystems and emphasize the need for further research to improve pollutant attenuation and biofilm recovery strategies in river streams.

Behavior space-temporal of biofilters based on hazelnut shells/sawdust treating pharmaceutical and personal care products from domestic wastewater

Nature-based solutions (NBS) such as biofiltration are an efficient, eco-friendly, and economical alternative for wastewater treatment under decentralized contexts. However, the influence on removing emerging contaminants (pharmaceuticals and personal care products or PPCPs), considering different typologies and seasonality fate, has been little studied. In this work, four lab-scale biofiltration typologies (BM: Biofilter + microorganisms, BEM: Biofilter + earthworms + microorganisms, BH: Biofilter + microorganisms + plants + earthworms or Biofilter hybrid, BPM: Biofilter + plants + microorganisms) were monitored seasonally (April-December, 250 days), being fed with rural domestic wastewater. Zantedeschia aethiopica (L.) and Eisenia foetida Savigny were used as biotic components, interacting with organic support components (hazelnut shells and sawdust) for removal of organic matter, nutrients, and 4 PPCPs (caffeine, ibuprofen, losartan, and triclosan). The mass balance of PPCPs was carried out considering the input (influent), output (effluent), support (soil), and plant (root and stem/leaf). The results showed that the different evaluated typologies removed close to 100 % COD, up to 89 % NH4+-N, and up to 99 % coliforms. Meanwhile, caffeine, ibuprofen, losartan, and triclosan were removed between 34 and 100 %. Seasonality or biofiltration typology was non-significantly influential (p > 0.05). However, biofilter hybrid and the warm season were the most efficient for removing organic matter, nutrients, coliforms, and PPCPs. The PPCPs' fate was plants/substrate/effluent with values up to 36, 95, and 64 %, respectively. The effluent was caffeine's main fate. Substrate was the main fate of ibuprofen, losartan, and triclosan. Plants uptake caffeine as a carbon source.

Potential of nature-based solutions to reduce antibiotics, antimicrobial resistance, and pathogens in aquatic ecosystems. a critical review

This comprehensive scientific review evaluates the effectiveness of nature-based solutions (NBS) in reducing antibiotics (ABs), combating antimicrobial resistance (AMR), and controlling pathogens in various aquatic environments at different river catchment levels. It covers conventional and innovative treatment wetland configurations for wastewater treatment to reduce pollutant discharge into the aquatic ecosystems as well as exploring how river restoration and saltmarshes can enhance pollutant removal. Through the analysis of experimental studies and case examples, the review shows NBS's potential for providing sustainable and cost-effective solutions to improve the health of aquatic ecosystems. It also evaluates the use of diagnostic indicators to predict NBS effectiveness in removing specific pollutants such as ABs and AMR. The review concludes that NBS are feasible for addressing the new challenges stemming from human activities such as the presence of ABs, AMR and pathogens, contributing to a better understanding of NBS, highlighting success stories, addressing knowledge gaps, and providing recommendations for future research and implementation.

Nature-based solutions for antibiotics and antimicrobial resistance removal in tertiary wastewater treatment: Microbiological composition and risk assessment

This field-scale study evaluates the seasonal effectiveness of employing nature-based solutions (NBSs), particularly surface flow and horizontal subsurface flow constructed wetland configurations, as tertiary treatment technologies for the removal of antibiotics (ABs) and antibiotic resistance genes (ARGs) compared to a conventional treatment involving UV and chlorination. Out of the 21 monitored ABs, 13 were detected in the influent of three tertiary wastewater treatments, with concentrations ranging from 2 to 1218 ng·L-1. The ARGs sul1 and dfrA1 exhibited concentrations ranging from 1 × 105 to 9 × 106 copies/100 mL. NBSs were better at reducing ABs (average 69 to 88 %) and ARGs (2-3 log units) compared to the conventional tertiary system (average 36 to 39 % and no removal to 2 log units) in both seasons. Taxonomic compositions in influent water samples shifted from wastewater-impacted communities (Actinomycetota and Firmicutes) to a combination of plant rhizosphere-associated and river communities in NBS effluents (Alphaproteobacteria). In contrast, the conventional technology showed no substantial differences in community composition. Moreover, NBSs substantially reduced the ecotoxicological risk assessment (cumulative RQs). Furthermore, NBSs reduced the ecotoxicological risk (cumulative RQs) by an average of over 70 % across seasons, whereas the benchmark technology only achieved a 6 % reduction. In conclusion, NBSs present a robust alternative for minimizing the discharge of ABs and ARGs into surface water bodies.

Flushing away the future: The effects of wastewater treatment plants on aquatic invertebrates

Wastewater treatment plants (WWTP) are essential infrastructure in our developing world. However, with the development and release of novel entities and without modern upgrades, they are ineffective at fully removing micropollutants before treated effluents are released back into aquatic environments. Thus, WWTPs may represent additional point source impacts to freshwater environments, further pressuring aquatic fauna and already vulnerable insect communities. Previous studies - mostly focusing on single WWTPs - have shown general trends of freshwater invertebrate communities becoming dominated by pollution tolerant taxa. To expand on these findings, the current study is the first to comprehensively investigate data on the effects of 170 WWTPs on invertebrate taxonomic composition. We compared data for several diversity and pollution indices, as well as the taxonomic composition both upstream and downstream of the WWTPs (366 sampling sites). In terms of abundance, the three most frequent and negatively impacted orders were the Plecoptera, Trichoptera and Gastropoda, while the Turbellaria, Hirudinea and Crustacea increased in abundance. Although strong changes in community composition were observed between upstream and downstream sites (mean species turnover of 61%), commonly used diversity indices were not sensitive to these changes, highlighting their potential inadequacy in accurately assessing ecological health. Our results indicate that WWTPs change downstream conditions in favour of pollution tolerant taxa to the detriment of sensitive taxa. Order-level taxonomic responses can be informative but should be interpreted with caution, since they can be driven by a few taxa, or opposing responses of species in the same group can result in an overall low order-level response. Upgrading WWTPs via additional treatment steps or merging may be beneficial, provided upstream sections are unimpacted and/or are in a good chemical and structural condition.

Analysis on the attenuation characteristics of PPCPs in surface water and their influencing factors based on a compilation of literature data

The attenuation characteristics of PPCPs play an important part in predicting their environmental concentrations. However, considerable uncertainty remains in reported laboratory data on the attenuation characteristics of PPCPs. In this analysis, we compile information on laboratory-observed photodegradation half-lives (t1/2), biodegradation t1/2, the organic carbon normalized adsorption constant (KOC) and field-observed overall attenuation t1/2 for PPCPs in water bodies from more than 200 peer-reviewed studies. To mitigate the effects of such uncertainty, we derive representative values (RV) for PPCP degradability from these records to better compare the characteristics of different PPCPs. We further examine the influence of experimental conditions and environmental drivers on the determination of t1/2 using difference analysis and correlation analysis. The results indicate that for laboratory photodegradation tests, different light sources, initial concentration and volume significantly affect t1/2, whereas there is no significant difference between values obtained from tests conducted in pure water and natural water. For biodegradation, laboratory-measured t1/2 values in batch, flume and column studies gradually decrease, marking the controlling role of experimental setup. Redox condition, initial concentration and volume are also recognized as important influencing factors. For adsorption, water-sediment ratio is the primary reaction parameter. As two frequently investigated factors, however, pH and temperature are not significant factors in almost all cases. In field observations, the persistence of carbamazepine, typically used as a tracer, is in doubt. Water depth and latitude are the most correlated drivers of t1/2, indicating the predominant status of photodegradation in the overall attenuation rates. These findings call for caution when selecting experimental parameters and environmental drivers in determining PPCP's attenuation rates and establishing PPCP fate models in the field.

Seasonal and longitudinal water quality dynamics in three effluent-dependent rivers in Arizona

Effluent-fed streams, which receive inputs from wastewater treatment plants, are becoming increasingly common across the globe as urbanization intensifies. In semi-arid and arid regions, where many natural streams have dried up due to over extraction of water, many streams rely completely on treated effluent to sustain baseflow during dry seasons. These systems are often thought of as ‘second-class’ or highly disturbed stream ecosystems, but they have the potential to serve as refuges for native aquatic biota if water quality is high, especially in areas where few natural habitats remain. In this study, we investigated seasonal and longitudinal water quality dynamics at multiple sites across six reaches of three effluent-dependent rivers in Arizona (USA) with the objective (1) to quantify changes in effluent water quality due to distance traveled and season/climate and (2) to qualify whether water quality conditions in these systems are sufficient to support native aquatic species. Study reaches ranged in length from 3 to 31 km and in geographic setting from low desert to montane conifer forest. We observed the lowest water quality conditions (e.g., elevated temperature and low dissolved oxygen) during the summer in low desert reaches, and significantly greater natural remediation of water quality in longer vs. shorter reaches for several factors, including temperature, dissolved oxygen and ammonia. Nearly all sites met or exceeded water quality conditions needed to support robust assemblages of native species across multiple seasons. However, our results also indicated that temperature (max 34.2 °C), oxygen levels (min 2.7 mg/L) and ammonia concentrations (max 5.36 mg/L N) may occasionally be stressful for sensitive taxa at sites closest to effluent outfalls. Water quality conditions may be a concern during the summer. Overall, effluent-dependent streams have the capacity to serve as refuges for native biota in Arizona, and they may become the only aquatic habitat available in many urbanizing arid and semi-arid regions.

Attenuation of organic pollutants and the effects of salinity and seasonality in a Mediterranean micro-estuary

Micro-estuaries are small ubiquitous transitional water bodies that are often located in semi-arid zones. Unlike the vastly studied large estuaries, micro-estuaries lack the ability to dilute and contain pollution from point and non-point sources due to low natural water discharges. Therefore, these diverse ecological systems are susceptible to pollutant loads due to prolonged water residence time and complex geochemical dynamics. Although this elevated anthropogenic stress limits their potential to provide ecological and recreational services, micro-estuaries have some traits similar to those found in wetlands, which provide a natural potential to retain and mitigate organic pollutants. A two consecutive years study conducted at the Alexander micro-estuary tracked the influx and outflux of a large organic pollutant mixture during base-flow and flood events. During the research period, 165 kg of active ingredients entered the micro-estuary and 160 kg flowed out to the Mediterranean Sea, suggesting negligible net attenuation. However, this broad picture conceals inner shifts in pollutant mixture loads, which contained 46 pesticides and 19 pharmaceuticals. Only a handful of pollutants were actually balanced, whereas most compounds were either removed or added to the flow, with no observed correlation to chemical properties. A prominent observation was the load increase along the flow for some pollutants during base-flow conditions. This trend, which was correlated with salinity elevation and was verified in lab experiments, suggests that seawater intrusion to the bottom of the estuary may increase desorption rates of pollutants from the estuary bed, creating an estuarine desorption magnification effect. The combination of strong anthropogenic stress with increased desorption rates severely limits the estuary's potential to mitigate pollutants, frequently transforming it into a pollution source rather than a sink.

Removal of pharmaceutical active compounds in wastewater by constructed wetlands: Performance and mechanisms

The occurrence of pharmaceutical active compounds (PhACs) in aquatic environments is a cause for concern due to potential adverse effects on human and ecosystem health. Constructed wetlands (CWs) are cost-efficient and sustainable wastewater treatment systems for the removal of these PhACs. The removal processes and mechanisms comprise a complex interplay of photodegradation, biodegradation, phytoremediation, and sorption. This review synthesized the current knowledge on CWs for the removal of 20 widely detected PhACs in wastewater. In addition, the major removal mechanisms and influencing factors are discussed, enabling comprehensive and critical understanding for optimizing the removal of PhACs in CWs. Consequently, potential strategies for intensifying CWs system performance for PhACs removal are discussed. Overall, the results of this review showed that CWs performance in the elimination of some pharmaceuticals was on a par with conventional wastewater treatment plants (WWTPs) and, for others, it was above par. Furthermore, the findings indicated that system design, operational, and environmental factors played important but highly variable roles in the removal of pharmaceuticals. Nonetheless, although CWs were proven to be a more cost-efficient and sustainable technology for pharmaceuticals removal than other engineered treatment systems, there were still several research gaps to be addressed, mainly including the fate of a broad range of emerging contaminants in CWs, identification of specific functional microorganisms, transformation pathways of specific pharmaceuticals, assessment of transformation products and the ecotoxicity evaluation of CWs effluents.

Modeling in-stream attenuation of N-nitrosodimethylamine and formaldehyde during urban river transportation based on seasonal and diurnal variation

Disinfection by-products (DBPs) discharged from sewage treatment plants (STPs) could harm downstream receiving waters and drinking water resources. In-stream attenuation of photo- and non-photodegradable DBPs during river transportation is currently not well understood. Here we sought to fill this knowledge gap by meta-data-analysis for modeling in-stream attenuation of DBPs. Data were collected along a treated-wastewater-dominated 1.6-km stretch of a river channel for 3 years and incorporated seasonal and diurnal patterns. Photo-irradiation and water temperature were the main factors responsible for in-stream attenuation of photodegradable N-nitrosodimethylamine (NDMA), and water temperature for that of non-photodegradable formaldehyde (FAH). The factors were incorporated into photo-dependent and -independent models to account for temporal variations in NDMA and FAH, respectively. Estimated mass recoveries of NDMA and FAH agreed well with observed values along the stretch. The models developed here offer a novel and useful tool for estimating levels of NDMA and FAH during river transportation.

Substituted diphenylamine antioxidants (SDPAs) in typical domestic wastewater treatment plants and Songhua River in the northeast of China

Limited studies focus on the occurrence, removal rate and seasonal variation of substituted diphenylamine antioxidants (SDPAs) in surface water and wastewater in China. In this paper, the detection method of SDPAs was established by the ultra-performance liquid chromatography-tandem mass spectrometry. Daily variations suggested that significant variations were found for the concentrations of some SDPAs in the influent. It was found that the SDPAs could be detected in all the effluent samples and C8/C8-DPA was the predominant compound in two WWTPs. The levels of most SDPAs in the effluent were much lower than that of influent, with the removal efficiencies of total SDPAs ranged from 57.9% to 84.2%. There were significant differences with the SDPA concentrations in the influent between different seasons. Higher concentrations of SDPAs were found at downstream than those of upstream. The results of this study provide more environmental occurrence data and new insights into the research on the environmental fate of these compounds.

Risk assessment of contaminants of emerging concern in the context of wastewater reuse for irrigation: An integrated modelling approach

Direct reuse of reclaimed wastewater (RWW) in agriculture has recently received increasing attention as a possible solution to water scarcity. The presence of contaminants of emerging concern (CECs) in RWW can be critical, as these chemicals can be uptaken in irrigated crops and eventually ingested during food consumption. In the present study, an integrated model was developed to predict the fate of CECs in water reuse systems where RWW is used for edible crops irrigation. The model was applied to a case study where RWW (originating from a municipal wastewater treatment plant) is discharged into a water channel, with subsequent irrigation of silage maize, rice, wheat and ryegrass. Environmental and human health risks were assessed for 13 CECs, selected based on their chemical and hazard characteristics. Predicted CEC concentrations in the channel showed good agreement with available measurements, indicating potential ecotoxicity of some CECs (estrogens and biocides) due to their limited attenuation. Plant uptake predictions were in good agreement with existing literature data, indicating higher uptake in leaves and roots than fruits. Notably, high uncertainties were shown for weakly acidic CECs, possibly due to degradation in soil and pH variations inside plants. The human health risk due to the ingestion of wheat and rice was assessed using the threshold of toxicological concern and the hazard quotient. Both approaches predicted negligible risk for most CECs, while sulfamethoxazole and 17α-ethinylestradiol exhibited the highest risk for consumers. Alternative scenarios were evaluated to identify possible risk minimization strategies (e.g., adoption of a more efficient irrigation system).

Unravelling the role of vegetation in the attenuation of contaminants of emerging concern from wetland systems: Preliminary results from column studies

Water pollution with contaminants of emerging concern (CECs) is widespread in water bodies due to the low effectiveness of industrial and urban wastewater treatment systems. In recent decades, the implementation of vegetation-based wastewater treatment systems such as wetlands has been observed to help solve this issue. However, there is a lack of knowledge regarding the removal percentage attributable to plants and how plants affect this removal improvement. In this study, we monitored planted (Phragmites australis) and unplanted sand columns to assess the effect of vegetation on the attenuation of 5 well-known CECs (benzotriazole, sulfamethoxazole, carbamazepine, bisphenol A, and diclofenac) and link it to the presence of different root exudates. The columns were operated in a continuous feeding mode for more than 6 months at 3 hydraulic loading rates (HLRs) (70, 140, and 280 mm d^-1). We found that the presence of vegetation increased CEC attenuation from no effect to more than 200% compared to the unplanted columns. The highest effect was observed for carbamazepine (94-200%), followed by diclofenac (22-171%), benzotriazole (48-127%), and sulfamethoxazole (no effect to 43%), depending on the tested HLR. Furthermore, the greater CEC attenuation in planted columns was linked to the release of certain root exudates that may shape the root microbiome. We expect our assay to be a starting point for exploring the role of root exudates in enhancing CEC removal efficiency in wastewater.

Designing field-based investigations of organic micropollutant fate in rivers

Organic micropollutants in rivers are emitted via diffuse and point sources like from agricultural practice or wastewater treatment plants (WWTP). Extensive laboratory and field experiments have been conducted to understand emissions and fate of these pollutants in freshwaters. Nevertheless, data is often difficult to compare since common protocols for appropriate approaches are largely missing. Thus, interpretation of the observed changes in substance concentrations and of the underlying fate of these compounds downstream of the chemical input into the river is still challenging. To narrow this research gap, (1) process understanding and (2) measurement approaches for field-based investigations are critically reviewed in this article. The review includes, on the one hand, processes that change the volume of the water (hydrological processes) and, on the other hand, processes that affect the substance mass within the water (distribution and transformation). Environmental boundary conditions for the purpose of better comparability of different attenuation studies, as well as promising state-of-the-art measurement approaches from different disciplines, are presented. This overview helps to develop a tailored procedure to assess turnover mechanisms of organic micropollutants under field conditions. In this respect, further research needs to standardize interdisciplinary approaches to increase the informative value of collected data.

Fate of wastewater contaminants in rivers: Using conservative-tracer based transfer functions to assess reactive transport

Interpreting the fate of wastewater contaminants in streams is difficult because their inputs vary in time and several processes synchronously affect reactive transport. We present a method to disentangle the various influences by performing a conservative-tracer test while sampling a stream section at various locations for chemical analysis of micropollutants. By comparing the outflow concentrations of contaminants with the tracer signal convoluted by the inflow time series, we estimated reaction rate coefficients and calculated the contaminant removal along a river section. The method was tested at River Steinlach, Germany, where 38 contaminants were monitored. Comparing day-time and night-time experiments allowed distinguishing photo-dependent degradation from other elimination processes. While photo-dependent degradation showed to be highly efficient for the removal of metroprolol, bisoprolol, and venlafaxine, its impact on contaminant removal was on a similar scale to the photo-independent processes when averaged over 24 h. For a selection of compounds analyzed in the present study, bio- and photodegradation were higher than in previous field studies. In the Steinlach study, we observed extraordinarily effective removal processes that may be due to the higher proportion of treated wastewater, temperature, DOC and nitrate concentrations, but also a higher surface to volume ratio from low flow conditions that favorizes photodegradation through the shallow water column and a larger transient storage than observed in comparable studies.

Contamination patterns and attenuation of pharmaceuticals in a temporary Mediterranean river

The contamination patterns and fate of pharmaceutically active compounds (PhACs) were investigated in the Evrotas River (Southern Greece). This is a temporary river with differing levels of water stress and water quality impairment in a number of its reaches. Three sampling campaigns were conducted in order to capture different levels of water stress and water quality. Four sampling sites located on the main channel of the Evrotas River were sampled in July 2015 (moderate stream flow), and June and September 2016 (low stream flow). Discharge of urban wastewater has been determined as the main source of pollution, with PhACs, nutrients and other physicochemical parameters considerably increasing downstream the wastewater treatment plant (WWTP) of Sparta city. Due to the pronounced hydrological variation of the Evrotas River, generally, the highest concentrations of PhACs have been detected during low flow conditions. Simultaneously, low flow resulted in an increased water travel time and consequently longer residence time that accounted for the higher attenuation of most PhACs. The average decrease in total concentration of PhACs within the studied waterbody segment (downstream of Sparta city) increased from 22% in July 2015 to 25% in June 2016 and 77% in September 2016. The PhACs with the highest average concentration decrease throughout the sampling campaigns were hydrochlorothiazide, followed by sotalol, carbamazepine, valsartan, and naproxen.

A Constructed Wetland for Treatment of an Impacted Waterway and the Influence of Native Waterfowl on its Perceived Effectiveness

A constructed, variable-flow treatment wetland was evaluated for its ability to reduce microbial loads from the Banklick Creek, an impacted recreational waterway in Northern Kentucky. For this study, levels of traditional (Escherichia coli and enterococci measured by culture and molecular techniques) and alternative fecal indicators (infectious somatic and F+ coliphage, Clostridium spp. and Clostridium perfringens by culture), potential pathogens (molecular signal of Campylobacter spp.) as well as various microbial source tracking (MST) markers (human fecal marker HF183 and avian fecal marker GFD) were monitored during the summer and early fall through five treatment stages within the Banklick Creek Wetland. No difference in concentrations of traditional or alternative fecal indicators were observed in any of the sites monitored. Microbial source tracking markers were employed to identify sources of fecal contamination within the wetland. Human marker HF183 concentrations at beginning stages of treatment were found to be significantly higher (P value range: 0.0016-0.0003) than levels at later stages. Conversely, at later stages of treatment where frequent bird activity was observed, Campylobacter and avian marker (GFD) signals were detected at significantly higher frequencies (P value range: 0.024 to <0.0001), and both signals were strongly correlated (P = 0.0001). Our study suggests constructed wetlands are an effective means for removal of microbial contamination in ambient waters, but reliance on general fecal indicators is not ideal for determining system efficacy or assessing appropriate remediation efforts.