Wastewater Inputs Research Articles

Developing nutrient criteria for the Grijalva basin, Mexico

Excess nutrient inputs are a major cause of aquatic ecosystem impairment worldwide. Increased total phosphorus (TP) and total nitrogen (TN) concentrations can lead to eutrophication affecting ecosystem functioning and environmental services provided by streams and rivers. Establishing numeric nutrient criteria is a strategy to reduce nutrient inputs into freshwater ecosystems. Our objective was to estimate nutrient concentrations that could be used as guides to establish nutrient criteria for TP and TN in the Grijalva basin, Mexico. We applied the frequency distribution method to water quality monitoring data for subregions (upper, middle, and lower Grijalva) and for the whole basin, considering two stream size categories. Nutrients were also compared among subregions, land uses, and stream sizes. Agriculture and urban areas showed higher nutrient concentrations than other land uses, probably due to the use of fertilizers and inputs of domestic and industrial wastewater. Higher nutrient concentrations were found in the middle Grijalva and in low-order streams. Nutrient concentrations at the 75th percentile for the reference sites were higher than those obtained at the 5th, 16.7th, and 25th percentiles for the general nutrient data, probably due to the high level of human disturbance in the Grijalva basin. Nutrient concentrations at the 25th percentile are probably too high to protect the aquatic ecosystems in the basin, while concentrations at the 5th percentile can be too restrictive for the basin. Based on our results, nutrient concentrations at the 16.7th percentile are proposed as a first approximation for nutrient criteria to protect river systems in the Grijalva basin.

Evaluation of benthic quality status and ecosystem functioning of soft bottom macrobenthos in the intertidal region with reference to Gulf of Khambhat, India

The Gulf of Khambhat is a dynamic intertidal regime influenced by variety of factors such as multiple water runoff from different rivers, wastewater input from industries and urban areas and natural phenomenon like tidal influence. Hence, it is necessary to evaluate the quality status of the intertidal areas along the gulf of Khambhat. Present study is a baseline study for the monitoring of ecosystem health of macrobenthos along the gulf of Khambhat coast. Macrobenthos are known as indicators for the organic enrichment, hence macrobenthos were used to assess the benthic quality status. BIOENV identified sediment quality parameters as most influential parameters and segregated the locations as sandy and sandy muddy habitat. Two robustly use biotic indices AMBI and BOPA were used to assess the ecological quality status of macrobenthos. From the biotic indices Alang was identified as most polluted location where as Diu as pristine habitat. Biological trait analysis (BTA) and Functional diversity indices (FD) explained the functioning of ecosystem along the Gulf of Khambhat where habitat heterogeneity was playing a major role in the species as well as functional diversity. Though biotic indices were showing positive results with functional diversity, no significant relationship was recorded.

Improving environmental monitoring of Vibrionaceae in coastal ecosystems through 16S rRNA gene amplicon sequencing

The Vibrionaceae family groups genetically and metabolically diverse bacteria thriving in all marine environments. Despite often representing a minor fraction of bacterial assemblages, members of this family can exploit a wide variety of nutritional sources, which makes them important players in biogeochemical dynamics. Furthermore, several Vibrionaceae species are well-known pathogens, posing a threat to human and animal health. Here, we applied the phylogenetic placement coupled with a consensus-based approach using 16S rRNA gene amplicon sequencing, aiming to reach a reliable and fine-level Vibrionaceae characterization and identify the dynamics of blooming, ecologically important, and potentially pathogenic species in different sites of the northern Adriatic Sea. Water samples were collected monthly at a Long-Term Ecological Research network site from 2018 to 2021, and in spring and summer of 2019 and 2020 at two sites affected by depurated sewage discharge. The 41 identified Vibrionaceae species represented generally below 1% of the sampled communities; blooms (up to ~ 11%) mainly formed by Vibrio chagasii and Vibrio owensii occurred in summer, linked to increasing temperature and particulate matter concentration. Pathogenic species such as Vibrio anguilllarum, Vibrio tapetis, and Photobacterium damselae were found in low abundance. Depuration plant samples were characterized by a lower abundance and diversity of Vibrionaceae species compared to seawater, highlighting that Vibrionaceae dynamics at sea are unlikely to be related to wastewater inputs. Our work represents a further step to improve the molecular approach based on short reads, toward a shared, updated, and curated phylogeny of the Vibrionaceae family.

Estimation of chemical oxygen demand in different water systems by near-infrared spectroscopy

To monitor environmental water pollution effectively and meet human water needs, it is crucial to develop a fast, simple, and accurate method for monitoring chemical oxygen demand (COD) in various water systems. In this study, COD prediction models for different water systems were developed by combining near-infrared (NIR) spectroscopy with partial least squares regression (PLSR). Samples of wastewater, surface water, and seawater were collected from Guangzhou, Guangdong Province, China. Three pretreatment methods were used to preprocess the spectra in order to improve the accuracy and minimalism of the model. We investigate the performance of two variable selection algorithms, namely, binary gray wolf optimization (BGWO) and competitive adaptive reweighting sampling (CARS). The results show that both BGWO and CARS improved the performance of the model in terms of higher accuracy and less wavelength input; both of the combined model performances were better than that of PLSR alone, and CARS-PLSR achieved the best results. Using CARS-PLSR, surface water, wastewater, and seawater model inputs were reduced by 96 %, 96 %, and 82 % as compared to the PLSR results, respectively, and the testing sets R2 reached 0.860, 0.815, and 0.692, respectively. The spectral variable selection algorithm could identify the important spectral variables between COD content and NIR spectra in three water systems, thereby improving the accuracy and simplicity of the PLSR model for COD prediction. Our results have important practical value for predicting COD content in different water systems by NIR spectroscopy.

Significant riverine inputs of typical plastic additives-phthalate esters from the Pearl River Delta to the northern South China Sea

Phthalate esters (PAEs) are representative additives used extensively in plastics. In this study, 15 PAEs were investigated at the eight riverine outlets of the Pearl River Delta (PRD). The total concentrations of Σ15PAEs, including both the dissolved and particulate phases, ranged from 562 to 1460 ng/L and 679 ng/L-2830 ng/L in the surface and bottom layers, respectively. Dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) dominated in the dissolved and suspended particulate matter (SPM) phases, respectively, accounting for >50 % and > 80 % of Σ15PAEs. Riverine input of wastewater from the PRD was possibly the primary source of the contamination. Higher levels of PAEs occurred at the eastern outlets than at the western ones. The dissolved and particulate PAEs varied seasonally, with significantly higher concentrations observed in the dry season than in the wet season. However, no significant differences of PAE levels in both phases were observed among low, medium, and high tides. The partitioning results demonstrated that SPM is important in the transportation of pollutants in estuaries, where more hydrophobic DEHP was predominantly transported by the SPM phase, while those more hydrophilic ones were regularly transported by the dissolved phase. The total annual flux of Σ15PAEs through the eight outlets to the SCS reached 1390 tons.

Detecting the sources of chemicals in the Black Sea using non-target screening and deep learning convolutional neural networks

The Black Sea is an important ecosystem, which is affected by various anthropogenic pressures, such as shipping activities and wastewater inputs from large coastal cities. Significant loads of chemical pollutants are being continuously brought in by major European rivers. This study investigated the spatial distribution of chemicals in the Ukrainian shelf (the northwestern part of the Black Sea) and their main sources. Chemical occurrence data used in the study was generated within the Joint Black Sea Surveys (JBSS), which took place in 2016 and 2017 as a part of the EU/UNDP EMBLAS II project (www.emblasproject.org). During the JBSS, seawater samples were analyzed by a non-target screening workflow using liquid chromatography high-resolution mass spectrometry (LC-HRMS). Open-source algorithms were applied to generate a combined dataset of 30,489 detected chemical signals and their intensities. Out of these, 35 compounds were tentatively identified by the application of a non-target screening identification workflow based on automated matching of their mass spectra against those in available mass spectral libraries. The dataset was used to generate images, representing spatial distribution of each of the signals. These images were then used as an input to a deep learning convolutional neural network classification model. The study resulted in the development of an open-source end-to-end workflow for the estimation of the pollution load by chemicals contributed by the two major inflowing rivers (Danube and Dnieper) and other, so far unidentified, sources. A dedicated dashboard was built to facilitate data visualization per detected signal/compound. The presented model proved to be especially useful at the prioritization of signals of unknown compounds, which is of key importance for the follow up structure elucidation efforts of bulky non-target screening data. The deep learning approach for peak prioritization of unknown chemicals in the environment has been used for the first time.

Linkages Between Optical and Molecular Signatures of Dissolved Organic Matter Along the Yangtze River Estuary-to-East China Sea Continuum

Changes in the molecular composition of dissolved organic matter (DOM) and its light-absorbing component (CDOM) along the river–coastal ocean continuum are crucial for better understanding the source and fate of DOM in coastal oceans. Both optical (absorbance and fluorescence) techniques and ultrahigh-resolution mass spectrometry have been widely used to trace DOM cycling. However, to the best of our knowledge, the linkage between these two techniques is rarely investigated along the river–coastal ocean continuum. In this regard, bulk characterization, optical techniques, and ultrahigh-resolution mass spectrometry [Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS)] were applied to determine the DOM chemistry along a spatial transect from the Yangtze River Estuary (YRE) to the East China Sea. The results showed that DOM in the YRE was mainly controlled by the mixing of freshwater and seawater. Besides terrestrial input, multiple sources (tributary input from the Huangpu River, wastewater input, and sediment resuspension and subsequent release at the turbidity maximum zone) have been identified. In addition, the linkages between CDOM and thousands of formulas were developed based on Spearman’s rank correlations between optical parameters and FT-ICR MS peaks. The linkages showed that the molecular groups associated with the optical parameters generally agreed with conventional biogeochemical interpretations. Nevertheless, each technique has its unique advantage and weakness in interpreting DOM composition. Therefore, the combination of the untargeted FT-ICR MS approach and optical techniques could be valuable for studying the DOM sources and transformation in large river estuarine systems.

Assessing the environmental performance of a novel coal mine brine treatment technique: A case in Poland

Although the energy transition results in decreased use of coal for power production, hard coal extraction will continue due to its importance in steel production and coal mine wastewater will continue generating after mines closure. The coal mining sector produces wastewater which results in environmental burdens and often contains valuable materials that can be treated to eliminate effluent discharge and recover contained materials. The aim of this study is to determine whether the implementation of a novel wastewater treatment technique in an existing coal wastewater treatment plant (WWTP) can improve both environmental performance and resource recovery potential. Our study assesses for the first time the environmental performance of the WWTP of Dębieńsko at the Upper Silesian Coal Basin, in Poland because coal mine effluents need to be treated to eliminate current environmental impacts on surface water bodies (rivers). The existing wastewater treatment system comprises reverse osmosis, evaporation and crystallization technologies. In the case of the novel ZERO BRINE technique, lab performance data is scaled-up and used for nanofiltration, reverse osmosis, electrodialysis and crystallization technologies. The environmental impacts analysis is performed with life cycle assessment (LCA) by considering mid-point impact categories (climate change, terrestrial acidification and fossil resource scarcity) and end-point damages (human health, ecosystems and resources). The functional unit is 1 m3 of coal mine wastewater input and a scenario is developed where the plant functionality concerns salt production. Results show that the implementation of the ZERO BRINE technique can improve the environmental performance of the WWTP for all considered impact categories due to a reduction in electricity consumption by 13% in the entire plant. Climate change, acidification, fossil resources scarcity, human health, ecosystems, and resources were improved by 16%, 13%, 12%, 25%, 21% and 13%, respectively. A sensitivity analysis is performed on the electricity consumption of electrodialysis which shows an additional improvement by 7% on all impacts. The ZERO BRINE technique produces both water and different types of salts. In this case, the multi-functionality of the system is addressed through substitution, while sensitivity analyses are carried out using mass and economic allocation methods.

Impacts of Human Activities and Environmental Changes on Spatial-Seasonal Variations of Metals in Surface Sediments of Zhanjiang Bay, China

This study investigated the total concentrations and geochemical compositions of metals (Cd, Cr, Cu, Ni, Pb, Zn, Fe and Mn) in surface sediments of Zhanjiang Bay (ZJB) in spring and summer, to assess the contamination status, mobility and influencing factors of spatial-seasonal changes of these metals. The average total concentration for each studied metal in the surface sediments of ZJB was 0.173 μg/g for Cd, 58.25 μg/g for Cr, 17.11 μg/g for Cu, 16.89 μg/g for Ni, 28.70 μg/g for Pb, 67.91 μg/g for Zn, 30.18 mg/g for Fe, and 275.5 μg/g for Mn during the investigation period. Generally higher total concentrations of metals were found in the channel and coastal sediments of ZJB compared with those in the central ZJB, which may be probably resulted by the input of Suixi river, domestic sewage and industrial wastewater. The grain size compositions and TOC contents also had influences on the distributions of metals in ZJB. In the channel, total metals and reducible and bioavailable fractions of metals generally showed decreased concentrations in summer compared with those in spring, suggesting the release of metals from sediments. Organic matter degradation and Fe and Mn (hydr)oxides reduction processes may contribute much to this phenomenon. Relatively high proportions of Cd and Zn (average of 21.7% and 14.6%, respectively) were associated with the acid soluble fraction, indicating their high risk to the environment. The combined assessment results of enrichment factor, contaminated factor and the percentages of acid soluble fraction indicated that Cd and Zn in the surface sediments of ZJB were generally contaminated and they had medium to high risk to the environment. The average values of pollution load index in the channel, coastal and central ZJB were 1.28, 0.93 and 0.81, respectively, indicating the deterioration of surface sediments in the channel of ZJB. More attention should be paid on the metals in surface sediments of the channel of ZJB.

Review of Thermochemical Technologies for Water and Energy Integration Systems: Energy Storage and Recovery

Thermochemical technologies (TCT) enable the promotion of the sustainability and the operation of energy systems, as well as in industrial sites. The thermochemical operations can be applied for energy storage and energy recovery (alternative fuel production from water/wastewater, in particular green hydrogen). TCTs are proven to have a higher energy density and long-term storage compared to standard thermal storage technologies (sensible and latent). Nonetheless, these require further research on their development for the increasing of the technology readiness level (TRL). Since TCTs operate with the same input/outputs streams as other thermal storages (for instance, wastewater and waste heat streams), these may be conceptually analyzed in terms of the integration in Water and Energy Integration System (WEIS). This work is set to review the techno-economic and environmental aspects related to thermochemical energy storage (sorption and reaction-based) and wastewater-to-energy (particular focus on thermochemical water splitting technology), aiming also to assess their potential into WEIS. The exploited technologies are, in general, proved to be suitable to be installed within the conceptualization of WEIS. In the case of TCES technologies, these are proven to be significantly more potential analogues to standard TES technologies on the scope of the conceptualization of WEIS. In the case of energy recovery technologies, although a conceptualization of a pathway to produce usable heat with an input of wastewater, further study has to be performed to fully understand the use of additional fuel in combustion-based processes.

Saline lakes as barriers against pollution: a multidisciplinary overview

Saline lakes are subject to numerous environmental impacts closely related to human activities, including mining, desiccation and pollution. These lakes are mostly located in arid and semi-arid regions located in endorheic basins, which combined with the low precipitation and high evaporation rates typical for these regions, may lead to the accumulation of pollutants. Saline lakes are polluted mainly through inputs of agricultural wastewater along with organic and inorganic wastes from domestic and industrial sources. The excessive anthropogenic loading of nutrients, especially nitrogen (N), can result in eutrophication of these ecosystems. Here, the importance of pollution in saline lakes was assessed, placing special emphasis on N pollution and its attenuation in aquatic interfaces. Two main interfaces are present in saline lakes: (1) the sediment-water interface; (2) the freshwater-saltwater interface. While the former is the most important one for microbial turnover, the latter plays also a key role in pollution attenuation based on solute transport by density-driven flows. The study of how saline lakes can attenuate N pollutants (e.g. nitrate) is a step forward in preserving the good ecological status of these ecosystems. This work highlights the need of integrating a wide range of techniques from different disciplines such as limnology, hydrogeology, geochemistry or microbial ecology for such studies. The effective application of conservation policies by managers will depend on the degree of knowledge of these systems.

Huge quantities of microplastics are “hidden” in the sediment of China's largest urban lake—Tangxun Lake

Microplastics (MPs) pollution in Tangxun Lake, the largest urban lake in China, was investigated. The average MPs pollution in sediment (1.81 ± 1.75 × 104 items kg−1) is at a high level, while the MPs in lakeshore water (917.77 ± 742.17 items m−3) is in the middle to low level compared with existing studies, which is related to the government's protection. Fragments and fibers are the most common shapes in sediment and water, respectively. MPs size <1 mm dominates in the sediment, while the MPs in water has a larger size. The distribution of MPs in the inner lake shows that pellets tend to “hidden” in sediments. Suspected MPs are randomly selected for polymer detection by Micro-Raman microscopy. Polypropylene (PP), polyethylene (PE) and polyethylene terephthalate (PET) are the most common polymer types in water, sediment and atmospheric deposition MPs samples. The input of wastewater, fishery and surrounding human activities are the main sources of MPs in sediment. Atmospheric deposition has a great impact on the distribution of MPs, while the contribution of surface runoff to lake MPs is not remarkable. In addition, MPs in sediments have exceeded the environmental carrying capacity. More attention should be focused on the sediment, where huge amounts of MPs are “hidden”.

Fungal Diversity in Two Wastewater Treatment Plants in North Italy.

In urban wastewater treatment plants, bacteria lead the biological component of the depuration process, but the microbial community is also rich in fungi (mainly molds, yeasts and pseudo-yeasts), whose taxonomical diversity and relative frequency depend on several factors, e.g., quality of wastewater input, climate, seasonality, and depuration stage. By joining morphological and molecular identification, we investigated the fungal diversity in two different plants for the urban wastewater treatment in the suburbs of the two major cities in Lombardia, the core of industrial and commercial activities in Italy. This study presents a comparison of the fungal diversity across the depuration stages by applying the concepts of α-, β- and ζ-diversity. Eurotiales (mainly with Aspergillus and Penicillium), Trichosporonales (Trichosporon sensu lato), Saccharomycetales (mainly with Geotrichum) and Hypocreales (mainly with Fusarium and Trichoderma) are the most represented fungal orders and genera in all the stages and both the plants. The two plants show different trends in α-, β- and ζ-diversity, despite the fact that they all share a crash during the secondary sedimentation and turnover across the depuration stages. This study provides an insight on which taxa potentially contribute to each depuration stage and/or keep viable propagules in sludges after the collection from the external environment.

Traffic-related sources may dominate urban water contamination for many organic contaminants

Urban runoff and wastewater/sewage input are majorly responsible for the contamination of urban streams. In streams where wastewater input is not a considerable input, the importance of urban runoff as a mechanism of contaminant transport and delivery from urban surfaces to receiving waters is even more apparent. Extensive studies on two such streams in Southern Ontario, Canada yielded data on the occurrence and levels of multiple contaminant groups (polycyclic aromatic hydrocarbons and quinones, benzotriazoles (BTs), BT ultraviolet stabilizers, organophosphate esters, herbicides) and the influence of factors such as temperature, rainfall characteristics, and land use. Here, we collectively examined the data from these studies to identify any trends and further insights. Using concentration-discharge relationships, we found that the transport dynamics of many particle-bound compounds are strikingly similar to each other, and to that of suspended solids in which they were quantified, suggesting a single, predominant source. Similar urban to rural ratios across compound groups and strong correlations with road density further support the existence of a dominant source and point to traffic as this source, respectively. Although road traffic had not previously been implicated as a major source of many of the investigated compound groups, their uses suggest that traffic-related sources are very plausible. Overall, this work highlights that traffic is a major source of a surprisingly wide array of organic contaminants to urban surfaces, and subsequently to nearby streams.

The Human Health Implications of Antibiotic Resistance in Environmental Isolates from Two Nebraska Watersheds.

ABSTRACTOne Health field-based approaches are needed to connect the occurrence of antibiotics present in the environment with the presence of antibiotic resistance genes (ARGs) in Gram-negative bacteria that confer resistance to antibiotics important in for both veterinary and human health. Water samples from two Nebraska watersheds influenced by wastewater effluent and agricultural runoff were tested for the presence of antibiotics used in veterinary and human medicine. The water samples were also cultured to identify the bacteria present. Of those bacteria isolated, the Gram-negative rods capable of causing human infections had antimicrobial susceptibility testing and whole-genome sequencing (WGS) performed to identify ARGs present. Of the 211 bacterial isolates identified, 37 belonged to pathogenic genera known to cause human infections. Genes conferring resistance to beta-lactams, aminoglycosides, fosfomycins, and quinolones were the most frequently detected ARGs associated with horizontal gene transfer (HGT) in the watersheds. WGS also suggest recent HGT events involving ARGs transferred between watershed isolates and bacteria of human and animal origins. The results of this study demonstrate the linkage of antibiotics and bacterial ARGs present in the environment with potential human and/or veterinary health impacts.IMPORTANCE One health is a transdisciplinary approach to achieve optimal health for humans, animals, plants and their shared environment, recognizing the interconnected nature of health in these domains. Field based research is needed to connect the occurrence of antibiotics used in veterinary medicine and human health with the presence of antibiotic resistance genes (ARGs). In this study, the presence of antibiotics, bacteria and ARGs was determined in two watersheds in Nebraska, one with agricultural inputs and the other with both agricultural and wastewater inputs. The results presented in this study provide evidence of transfer of highly mobile ARG between environment, clinical, and animal-associated bacteria.

Saltmarsh sediments with wastewater input emit more carbon greenhouse gases but less N2O than mangrove sediments

Wastewater discharge and salt marsh invasion are two main disturbances in global mangrove wetland ecosystems, but their combined effects on greenhouse gas (GHG) emissions remain unclear. Here, we performed a laboratory incubation experiment by adding wastewater (aquaculture and domestic wastewater) to mangrove and salt marsh sediments. Dissolved GHGs (CO2, CH4 and N2O) and environmental parameters were measured over a time series of 50 days. The nitrification and denitrification rates and corresponding functional gene abundances (AOA, AOB, nirS, and narG) were also quantified. The results show that wastewater addition significantly increased GHG emissions and global warming potential (GWP) in wetland sediments (p < 0.05 for both). Compared with mangroves, salt marsh sediments produced more carbon GHGs (CO2 and CH4) but less N2O after wastewater input. These different stimulatory effects could be explained by the nitrogen and carbon substrate availability, organic matter quality, and functional gene abundances in sediments. Assessing GHG emissions as CO2 equivalents, future scenarios of increasing salt marsh invasion with wastewater addition would increase the GWP caused by CO2 and CH4, decrease blue carbon sequestration potential in wetlands, and decrease the GWP caused by N2O and total GWP, indicating a great impact on global climate change and important implications for managing coastal wetlands.

Land Use Change to Reduce Freshwater Nitrogen and Phosphorus will Be Effective Even with Projected Climate Change

Recent studies have demonstrated that projected climate change will likely enhance nitrogen (N) and phosphorus (P) loss from farms and farmland, with the potential to worsen freshwater eutrophication. Here, we investigate the relative importance of the climate and land use drivers of nutrient loss in nine study catchments in Europe and a neighboring country (Turkey), ranging in area from 50 to 12,000 km2. The aim was to quantify whether planned large-scale, land use change aimed at N and P loss reduction would be effective given projected climate change. To this end, catchment-scale biophysical models were applied within a common framework to quantify the integrated effects of projected changes in climate, land use (including wastewater inputs), N deposition, and water use on river and lake water quantity and quality for the mid-21st century. The proposed land use changes were derived from catchment stakeholder workshops, and the assessment quantified changes in mean annual N and P concentrations and loads. At most of the sites, the projected effects of climate change alone on nutrient concentrations and loads were small, whilst land use changes had a larger effect and were of sufficient magnitude that, overall, a move to more environmentally focused farming achieved a reduction in N and P concentrations and loads despite projected climate change. However, at Beyşehir lake in Turkey, increased temperatures and lower precipitation reduced water flows considerably, making climate change, rather than more intensive nutrient usage, the greatest threat to the freshwater ecosystem. Individual site responses did however vary and were dependent on the balance of diffuse and point source inputs. Simulated lake chlorophyll-a changes were not generally proportional to changes in nutrient loading. Further work is required to accurately simulate the flow and water quality extremes and determine how reductions in freshwater N and P translate into an aquatic ecosystem response.

Mercury concentrations and stable isotopes (δ15N and δ13C) in fish muscle indicate human impacts in tropical coastal lagoons

Coastal lagoons are essential nursery habitats of many marine fishes, but they are often sites of intense human activities that impact water quality and potentially the fish using these habitats. We compared the variability in nutrient uptake (using δ15N and δ13C) and total mercury (THg) levels in juveniles and adults of three common species in two lagoons on the central Mexican coast of the Pacific Ocean during the wet and dry seasons. One of three species, Achirus mazatlanus had higher THg, δ15N, and δ13C levels in the lagoon with the greatest wastewater inputs (Barra de Navidad). Delta13C varied seasonally for all three species and THg was higher in the dry season for Lutjanus argentiventris and in males of A. mazatlanus. Our results demonstrate that mercury and stable isotopes can identify impacts of human activities on estuarine ichthyofauna and the importance of understanding seasonal and spatial variability of measures that could impact monitoring and predictions of impacts in these lagoons.

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).

Caffeine and Paraxanthine as Tracers of Anthropogenic Wastewater in Coastal Lagoons in Yucatan, Mexico.

Due to karstic bedrock geology and poor wastewater management practices, anthropogenic activities are impacting water quality in Yucatan's aquatic systems. Specifically, raw wastewater inputs to the aquifer subsequently flow to coastal lagoons through groundwater fluxes. This study establishes the presence of anthropogenic wastewater by measuring caffeine and its metabolite, paraxanthine, in four of Yucatan's major coastal lagoons: Celestun, Chelem, Dzilam de Bravo, and Ria Lagartos. Concentrations of caffeine ranged from non-detected (ND) to 2390ng L-1 and paraxanthine from ND to 212ng L-1, which correspond with pollution threats from anthropogenic wastewater inputs. The potential sources are: (1) direct in situ discharges from nearby urban settlements; and (2) contribution from submerged groundwater discharges. Overall, results indicate the potential of caffeine as an environmental tracer of anthropogenic wastewater contamination for the region.