Comparative whole effluent toxicity assessment of wastewater treatment plant effluents using Daphnia magna

Ecotoxicological evaluation of surface waters in Northern Namibia

The increasing pressure on freshwater systems due to intensive anthropogenic use is a big challenge in central-northern Namibia and its catchment areas, the Kunene and the Kavango Rivers, and the Cuvelai-Etosha Basin, that provide water for more than 1 million people. So far, there is no comprehensive knowledge about the ecological status and only few knowledge about the water quality. Therefore, it is crucial to learn about the state of the ecosystem and the ecological effects of pollutants to ensure the safe use of these resources. The surface waters of the three systems were sampled, and three bioassays were applied on three trophic levels: algae, daphnia, and zebrafish embryos. Additionally, in vitro assays were performed to analyze mutagenicity (Ames fluctuation), dioxin-like potential (micro-EROD), and estrogenicity (YES) by mechanism-specific effects. The results show that acute toxicity to fish embryos and daphnia has mainly been detected at all sites in the three catchment areas. The systems differ significantly from each other, with the sites in the Iishana system showing the highest acute toxicity. At the cellular level, only weak effects were identified, although these were stronger in the Iishana system than in the two perennial systems. Algae growth was not inhibited, and no cytotoxic effects could be detected in any of the samples. Mutagenic effects and an estrogenic potential were detected at three sites in the Iishana system. These findings are critical in water resource management as the effects can adversely impact the health of aquatic ecosystems and the organisms within them.

Toxicity and chemical characterization of shale gas wastewater discharged to the receiving water: Evidence from toxicity identification evaluation

Flowback and produced water (FPW) generated from shale gas extraction is a complex mixture consisting of injected drilling fluid, deep formation water, and byproducts of downhole reactions. Limited knowledge is available regarding the impact of discharged FPW on surface water in China. With the development of shale gas exploitation, this emphasizes an urgent need for comprehensive assessments and stringent regulations to ensure the safe disposal of shale gas extraction-related wastewater. Herein, we explored potential impacts of treated shale gas wastewater discharged into a local river in southwest China through toxicity identification evaluation (TIE). Results revealed that organics and particulates significantly contributed to the overall toxicity of the treated FPW wastewater. Through target and suspect chemical analyses, various categories of organic contaminants were detected, including alkanes, aromatic hydrocarbons, biocides, phenols, and phthalates. Furthermore, non-target analysis uncovered the presence of surfactant-related contaminants in tissues of exposed organisms, but their contribution to the observed toxicity was unclear due to the lack of effect data for these compounds. Higher toxicity was found at the discharge point compared with upstream sites; however, the toxicity was rapidly mitigated due to dilution in the receiving river, posing little impact on downstream areas. Our study highlighted the importance of monitoring toxicity and water quality of FPW effluent even though dilution could be a viable approach when the water volume in the discharge was small.

Metabolomics revealed disruptions in amino acid and antioxidant biochemistry in Daphnia magna exposed to industrial effluents associated with plastic and polymer production

Industrial wastewater effluents are a major source of chemicals in aquatic environments, and many of these chemicals may negatively impact aquatic life. In this study, the crustacean Daphnia magna, a common model organism in ecotoxicity studies, was exposed for 48 h to nine different industrial effluent samples from manufacturing facilities associated with the production of plastics, polymers, and coating products at a range of dilutions: 10, 25, 50, 100% (undiluted). A targeted metabolomic-based approach using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to quantify polar metabolites from individual daphnids that survived the 48 h exposure. Multivariate analyses and metabolite changes revealed metabolic perturbations across all effluent samples studied, with non-monotonic responses and both up and downregulation relative to the unexposed control. Pathway analyses indicated the disruption of similar and distinct pathways, mostly connected to protein synthesis, amino acid metabolism, and antioxidant processes. Overall, we observed disruptions in Daphnia biochemistry that were similar across the effluent samples, but with unique features for each effluent sample. Additionally, non-monotonic heightened responses suggested additive and/or synergistic interactions between the chemicals within the industrial effluents. These findings demonstrate that targeted metabolomic approaches are a powerful tool for the biomonitoring of aquatic ecosystems in the context of complex mixtures, such as industrial wastewater effluents.

Pharmaceuticals, hazard and ecotoxicity in surface and wastewater in a tropical dairy production area in Latin America

Pharmaceuticals comprise a complex group of emerging pollutants. Despite the significant number of pharmaceuticals used in veterinary medicine, the input of these compounds into the environment due to livestock activities has been scarcely described. This work assays for the first time in Central America the occurrence of pharmaceuticals in farm wastewater in an area devoted to dairy production, and in the surrounding surface waters. Among 69 monitored pharmaceuticals, a total of eight compounds were detected in wastewater samples collected from seven dairy farms after three sampling campaigns. Six pharmaceuticals were considered either of high (albendazole, lovastatin and caffeine) or intermediate estimated hazard (ciprofloxacin, acetaminophen and ketoprofen) based on the HQ approach, while 26% of the samples were considered of high estimated hazard according to the cumulative ∑HQ approach. Similarly, when ecotoxicological tests were applied, all the samples showed some level of toxicity towards Daphnia magna, and most samples towards Vibrio fischeri and Lactuca sativa. Fourteen pharmaceuticals were detected in surface water samples collected in the surroundings of the dairy production farms, including rural and urban areas. Seven out of these compounds showed high estimated risk (risperidone, diphenhydramine, trimethoprim, fluoxetine, ofloxacin, caffeine and ibuprofen), while three (gemfibrozil, ciprofloxacin and cephalexin) exhibited intermediate estimated risk. In a similar worrisome way, 27% of these samples were estimated to pose high environmental risk according to the pharmaceutical content. Despite being nontoxic for D. magna or V. fischeri, frequent inhibition (>20%) of GI in L. sativa was determined in 34% of surface water samples; such findings raise concern on the apparent inceptive environmental pollution and risk within the area. According to the pharmaceutical content patterns in both kinds of studied matrices, no clear evidence of significant contamination in surface water due to livestock activities could be retrieved, suggesting a main role of urban influence.

A critical review on quantitative evaluation of aqueous toxicity in water quality assessment

Conventional chemical techniques have inherent limitations in detecting unknown chemical substances in water. As a result, effect-based methods have emerged as a viable alternative to overcome these limitations. These methods provide more accurate and intuitive evaluations of the toxic effects of water. While numerous studies have been conducted, only a few have been applied to national water quality monitoring. Therefore, it is crucial to develop toxicity evaluation methods and establish thresholds based on quantifying toxicity. This article provides an overview of the development and application of bioanalytical tools, including in vitro and in vivo bioassays. The available methods for quantifying toxicity are then summarized. These methods include aquatic life criteria for assessing the toxicity of a single compound, comprehensive wastewater toxicity testing for all contaminants in a water sample (toxicity units, whole effluent toxicity, the potential ecotoxic effects probe, the potential toxicology method, and the lowest ineffective dilution), methods based on mechanisms and relative toxicity ratios for substances with the same mode of action (the toxicity equivalency factors, toxic equivalents, bioanalytical equivalents), and effect-based trigger values for micropollutants. The article also highlights the advantages and disadvantages of each method. Finally, it proposes potential areas for applying toxicity quantification methods and offers insights into future research directions. This review emphasizes the significance of enhancing the evaluation methods for assessing aqueous toxicity in water quality assessment.

Environmental metabolomics uncovers oxidative stress, amino acid dysregulation, and energy impairment in Daphnia magna with exposure to industrial effluents

Anthropogenic activities are regarded as point sources of pollution entering freshwater bodies worldwide. With over 350,000 chemicals used in manufacturing, wastewater treatment and industrial effluents are comprised of complex mixtures of organic and inorganic pollutants of known and unknown origins. Consequently, their combined toxicity and mode of action are not well understood in aquatic organisms such as Daphnia magna. In this study, effluent samples from wastewater treatment and industrial sectors were used to examine molecular-level perturbations to the polar metabolic profile of D. magna. To determine if the industrial sector and/or the effluent chemistries played a role in the observed biochemical responses, Daphnia were acutely (48 h) exposed to undiluted (100%) and diluted (10, 25, and 50%) effluent samples. Endogenous metabolites were extracted from single daphnids and analyzed using targeted mass spectrometry-based metabolomics. The metabolic profile of Daphnia exposed to effluent samples resulted in significant separation compared to the unexposed controls. Linear regression analysis determined that no single pollutant detected in the effluents was significantly correlated with the responses of metabolites. Significant perturbations were uncovered across many classes of metabolites (amino acids, nucleosides, nucleotides, polyamines, and their derivatives) which serve as intermediates in keystone biochemical processes. The combined metabolic responses are consistent with oxidative stress, disruptions to energy metabolism, and protein dysregulation which were identified through biochemical pathway analysis. These results provide insight into the molecular processes driving stress responses in D. magna. Overall, we determined that the metabolic profile of Daphnia could not be predicted by the chemical composition of environmentally relevant mixtures. The findings of this study demonstrate the advantage of metabolomics in conjunction with chemical analyses to assess the interactions of industrial effluents. This work further demonstrates the ability of environmental metabolomics to characterize molecular-level perturbations in aquatic organisms exposed to complex chemical mixtures directly.

On-farm Occurrence of Pharmaceuticals and Their Environmental Hazard: Case Study of a Tropical Dairy farm

Animal husbandry wastewaters represent an important source of pharmaceuticals into the environment. This work aimed to evaluate the occurrence of pharmaceuticals and their hazard in wastewater from a model dairy farm from Costa Rica. Among the seven pharmaceuticals detected (acetaminophen, caffeine, carbamazepine, ibuprofen, ketoprofen, risperidone, sulfamethazine), caffeine, ibuprofen and acetaminophen showed the highest concentrations, while caffeine, carbamazepine and risperidone were the most frequently detected compounds. High (HQ ≥ 1) or medium (0.1 ≤ HQ < 1) hazard were estimated for three (caffeine, ibuprofen, risperidone) and two (acetaminophen, ketoprofen) pharmaceuticals, respectively; similarly, high overall hazard (∑HQ) and significant ecotoxicity were determined in samples from all sampling points. According to our results, the release of these aqueous matrices is a matter of environmental concern, as the treated wastewater is used for farm irrigation or directly released into nearby water streams. This work contributes to the knowledge on the scarcely described occurrence and risk of pharmaceuticals in Latin American regions.

Towards Sustainable Wastewater Treatment: Bioindication as a Technique for Supporting Treatment Efficiency Assessment

Constructed wetlands (CWs) are a promising alternative for conventional methods of wastewater treatment. However, the biggest challenge in wastewater treatment is the improvement of the technology used so that it is possible to remove micropollutants without additional costs. The impact of wastewater treatment in CWs on toxicity towards Aliivibrio fischeri, Daphnia magna and Lemna minor was investigated. The effects of feeding regime (wastewater fed in five batches per week at a batch volume of 1 L, or twice per week at a batch volume of 2.5 L) and the presence of pharmaceuticals (diclofenac and sulfamethoxazole), as well as the presence of Miscantus giganteus plants in CW columns (twelve of the 24 columns that were planted) were analyzed. A reduction in toxicity was observed in all experimental setups. The effluents from constructed wetlands were classified as moderately toxic (average TU for A. fischeri, D. magna and L. minor was 0.9, 2.5 and 5.5, respectively). The feeding regime of 5 days of feeding/2 days of resting resulted in a positive impact on the ecotoxicological and chemical parameters of wastewater (removal of TOC, N-NH₄ and pharmaceuticals). Extended exposure of Miscantus giganteus to the wastewater containing pharmaceuticals resulted in elevated activity of antioxidant enzymes (catalase and superoxide dismutase) in leaf material.

The ECOTOXicology Knowledgebase: A Curated Database of Ecologically Relevant Toxicity Tests to Support Environmental Research and Risk Assessment

The need for assembled existing and new toxicity data has accelerated as the amount of chemicals introduced into commerce continues to grow and regulatory mandates require safety assessments for a greater number of chemicals. To address this evolving need, the ECOTOXicology Knowledgebase (ECOTOX) was developed starting in the 1980s and is currently the world's largest compilation of curated ecotoxicity data, providing support for assessments of chemical safety and ecological research through systematic and transparent literature review procedures. The recently released version of ECOTOX (Ver 5, www.epa.gov/ecotox) provides single-chemical ecotoxicity data for over 12,000 chemicals and ecological species with over one million test results from over 50,000 references. Presented is an overview of ECOTOX, detailing the literature review and data curation processes within the context of current systematic review practices and discussing how recent updates improve the accessibility and reusability of data to support the assessment, management, and research of environmental chemicals. Relevant and acceptable toxicity results are identified from studies in the scientific literature, with pertinent methodological details and results extracted following well-established controlled vocabularies and newly extracted toxicity data added quarterly to the public website. Release of ECOTOX, Ver 5, included an entirely redesigned user interface with enhanced data queries and retrieval options, visualizations to aid in data exploration, customizable outputs for export and use in external applications, and interoperability with chemical and toxicity databases and tools. This is a reliable source of curated ecological toxicity data for chemical assessments and research and continues to evolve with accessible and transparent state-of-the-art practices in literature data curation and increased interoperability to other relevant resources. Environ Toxicol Chem 2022;41:1520-1539. © 2022 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Polystyrene nanoplastics and wastewater displayed antagonistic toxic effects due to the sorption of wastewater micropollutants

The knowledge about the interaction of nanoplastics with other aquatic pollutants and their combined effects on biota is very scarce. In this work, we studied the interaction between polystyrene nanoplastics (PS NPs) (30 nm) and the micropollutants in a biologically treated wastewater effluent (WW). The capacity of PS NPs to sorb micropollutants was studied as well as their single and combined toxicity towards three freshwater organisms: the recombinant bioluminescent cyanobacterium, Anabaena sp. PCC 7120 CPB4337; the duckweed, Spirodela polyrhiza and the cladoceran, Daphnia magna. The endpoints were the inhibition of bioluminescence, the growth inhibition of the aquatic plant and the immobilization of D. magna after 24, 72 and 48 h of exposure, respectively. Combination Index (CI)-isobologram method was used to quantify mixture toxicity and the nature of interactions. PS NPs sorbed a variety of chemicals present in WW as micropollutants in a range of tens of ng/L to μg/L. It was found that those pollutants with positive charge were the main ones retained onto PS NPs, which was attributed to the electrostatic interaction with the negatively charged PS NPs. Regarding the toxicological effects, single exposure to PS NPs affected the three tested organisms. However, single exposure to WW only had a negative impact on the cyanobacterium and S. polyrhiza with no observed toxicity to D. magna. Regarding PS NPs-WW combined exposure, a reduction of toxicity in comparison with single exposure was observed probably due to the sorption of micropollutants onto PS NPs, which resulted in lower bioavailability of the micropollutants. In addition, the formation of PS NPs-WW heteroaggregates was observed which could result in lower bioavailability of PS NPs and sorbed micropollutants, thus lowering toxicity. This study represents a near-realistic scenario approach to the potential sorption of wastewater pollutants onto nanoplastics that could alter the toxicological effect on the biota.

Chemical and biological tracking in decentralized sanitation systems: The case of artificial constructed wetlands

Given that the social and economic sustainability of rural areas is highly based on the protection of natural resources, biodiversity and human health, simple-operated and cost-effective wastewater treatment systems, like artificial constructed wetlands (CWs), are widely proposed for minimizing the environmental and human impact of both water and soil pollution. Considering that the optimization of wastewater treatment processes is vital for the reduction of effluents toxic potential, there is imperative need to establish appropriate management strategies for ensuring CW performance and operational efficiency. To this end, the present study aimed to assess the operational efficiency of a horizontal free water surface CW (HFWS-CW) located in a world heritage area of Western Greece, via a twelve-month duration Toxicity Identification Evaluation (TIE)-like approach, including both chemical and biological tracking tools. Conventional chemical tracking, by means of pH, conductivity, total COD, and nitrogen-derived components, like nitrates and ammonia-nitrogen, were monthly recorded in both influents and effluents to monitor whether water quality standards are maintained, and to assess potent CW operational deficiencies occurring over time. In parallel, Whole Effluent Toxicity (WET) bioassays were thoroughly applied, using freshwater algae and higher plant species (producers), crustaceans and rotifers (consumers), as well as human lymphocytes (in terms of Cytokinesis Block Micronucleus assay) to evaluate the acute and short-term toxic and hazardous potential of both influents and effluents. The integrated analysis of abiotic (physicochemical parameters) and biotic (toxic endpoints) parameters, as well as the existence of "cause-effect" interrelations among them, revealed that CW operational deficiencies, mainly based on poorly removal rates, could undermine the risk posed by treated sewage. Those findings reinforce the usage of WET testing, thus giving rise to the importance of applying appropriate water management strategies and optimization actions, like oxygen enrichment of surface and bottom of HFWS-CW basins, expansion of the available land, the enhancement of bed depth and seasonal harvesting of plants, for ensuring sewage quality, in favor of water resources protection and sustainable growth in rural areas.

Pharmaceuticals in farms and surrounding surface water bodies: Hazard and ecotoxicity in a swine production area in Costa Rica

The presence of pharmaceuticals in the environment is known to have multiple origins; livestock activities comprise one scarcely studied source, both globally and specially in Latin-America. This work aims to study the occurrence of pharmaceuticals in wastewater from swine farms and their surrounding surface waters, in a highland livestock production area of Costa Rica. The monitoring of 70 pharmaceutical active compounds resulted in the detection of 10 molecules in farm wastewater (influents and effluents of the on-farm treatment system), including compounds of animal and human use. A 57% of effluents showed high hazard (ΣHQ > 1), mainly due to the compounds risperidone, ketoprofen, ibuprofen and naproxen. Additionally, ecotoxicological tests with Daphnia magna and Microtox classified at least 21% of the effluents as very toxic (10 < TU ≤ 100); likewise, 86% of effluents exhibited germination index (GI) inhibition values over 90% for Lactuca sativa. Seven molecules were detected in surface water, six of them of human use (1,7-dimethylxanthine, caffeine, cephalexin, carbamazepine, gemfibrozil, ibuprofen) and one (acetaminophen) of dual (human and veterinary) use; nonetheless, most of the detections were found in sampling points closer to human settlements than animal farms. Considering the set of molecules and their distribution, the livestock influence on surface water seems minimal in comparison with the urban influence. Only 16% of surface water samples showed high risk, mainly due to ibuprofen, gemfibrozil and caffeine; similarly, 45% samples presented GI inhibition >20% (no toxicity was determined towards Daphnia magna or Microtox). These findings in surface water suggest an incipient environmental risk in the area.

Ecotoxicity profile of heavily contaminated surface water of two rivers in Tunisia

Persistent organic and inorganic contaminants generated by industrial effluent wastes poses a threat to the maintenance of aquatic ecosystems and public health. The Khniss and Hamdoun rivers, located in the central-east of Tunisia, receive regularly domestic and textile wastewater load. The present study aimed to survey the water quality of these rivers using physicochemical, analytical and toxicological approaches. In the physicochemical analysis, the recorded levels of COD and TSS in both samples exceed the Tunisian standards. Using the analytical approach, several metals and some textile dyes were detected. Indeed, 17 metals were detected in both samples in varying concentrations, which do not exceed the Tunisian standards. The sources of metals pollution can be of natural and anthropogenic origin. Three textile disperse dyes were detected with high levels compared to other studies: the disperse orange 37 was detected in the Khniss river with a concentration of 6.438 μg/L and the disperse red 1 and the disperse yellow 3 were detected in the Hamdoun river with concentrations of 3.873 μg/L and 1895 μg/L, respectively. Textile activities were the major sources of disperse dyes. For both samples, acute and chronic ecotoxicity was observed in all the studied organisms, however, no genotoxic activity was detected. The presence of metals and textile disperse dyes could be associated with the ecotoxicological effects observed in the river waters, in particular due to the industrial activity, a fact that could deteriorate the ecosystem and therefore threaten the human health of the population living in the study areas. Combining chemical and biological approaches, allowed the detection of water ecotoxicity in testing organisms and the identification of possible contributors to the toxicity observed in these multi-stressed water reservoirs.

Occurrence of pharmaceuticals, hazard assessment and ecotoxicological evaluation of wastewater treatment plants in Costa Rica

The continuous release of pharmaceuticals from WWTP effluents to freshwater is a matter of concern, due to their potential effects on non-target organisms. The occurrence of pharmaceuticals in WWTPs and their associated hazard have been scarcely studied in Latin American countries. This study aimed at monitoring for the first time the occurrence of 70 pharmaceutical active compounds (PhACs) in WWTPs across Costa Rica; the application of the hazard quotient (HQ) approach coupled to ecotoxicological determinations permitted to identify the hazard posed by specific pharmaceuticals and toxicity of the effluents, respectively. Thirty-three PhACs were found, with 1,7-dimethylxanthine, caffeine, acetaminophen, ibuprofen, naproxen, ketoprofen and gemfibrozil being the most frequently detected (influents/effluents). HQ for specific pharmaceuticals revealed 24 compounds with high/medium hazard in influents, while the amount only decreased to 21 in effluents. The top HQ values were obtained for risperidone, lovastatin, diphenhydramine and fluoxetine (influent/effluent samples), plus caffeine (influent) and trimethoprim (effluent). Likewise, the estimation of overall hazard in WWTP samples (sum of individual HQ, ∑HQ) demonstrated that every influent and 96% of the effluents presented high hazard towards aquatic organisms. Ecotoxicological analysis (Daphnia magna, Lactuca sativa and Microtox test) revealed that 16.7% of the effluents presented toxicity towards all benchmark organisms; the phytotoxicity was particularly frequent, as inhibition values ≥20% in the germination index for L. sativa were obtained for all the effluents. The ∑HQ approach estimated the highest hazard in urban wastewater, while the ecotoxicological results showed the highest toxicity in hospital and landfill wastewater. Likewise, ecotoxicological results and ∑HQ values showed a rather poor correlation; instead, better correlations were obtained between ecotoxicological parameters and HQ values for some individual pharmaceuticals such as cephalexin and diphenhydramine. Findings from this study provide novel information on the occurrence of pharmaceuticals and the performance of WWTPs in the tropical region of Central America.

Ecotoxicological assessment of effluents from Brazilian wastewater treatment plants using zebrafish embryotoxicity test: A multi-biomarker approach

Effluent from wastewater treatment plants (WWTPs) remains one of the major pollutants of aquatic environments; however, knowledge about its ecotoxic effects at fish early life stages is limited. The ecotoxicity of effluent from Brazilian WWTPs was herein analyzed based on responses of multiple biomarkers in the zebrafish embryotoxicity test (ZET). Ecotoxicity was analyzed based on mortality rate, hatching rate, spontaneous movement rate (neurotoxicity), heart rate (cardiotoxicity), frequency of morphological changes and morphometric parameters during 144 h exposure time. Results showed that embryos exposed to affluent and effluent presented high mortality rate and delayed hatching rate, as well as changes in morphometric parameters. Exposed embryos also showed physiological, sensory, skeletal and muscular changes, which confirms that the ecotoxic effect of WWTPs effluent is systemic and associated with the presence of several pollutants, even at low concentrations (mixture toxicity). The present study is pioneer in using responses of multiple biomarkers in ZET as suitable approach to assess the ecotoxicity of WWTPs effluent in developing countries, as well as to add value and contribute to studies on WWTPs worldwide. Zebrafish is a suitable vertebrate model to assess the ecotoxicity of WWTP effluent.

Elimination of the hormesis phenomenon by the use of synthetic sea water in a toxicity test towards Aliivibrio fischeri

Hormesis is an ecotoxicological phenomenon referred to as the biphasic dose-response effect. At a low concentration of toxic substances, a hormetic stimulating effect occurs, while an inhibitory effect occurs at higher concentrations. The phenomenon of hormesis may hinder the interpretation of toxicity test results and lower the actual toxicity of test samples. In this study, a hormesis phenomenon was observed and analysed during toxicity tests of wastewater from constructed wetlands containing two pharmaceutical substances, diclofenac (DCF) and sulfamethoxazole (SMX), against the marine bacteria Aliivibrio fischeri. To eliminate the hormesis phenomenon, a change in the diluent (ISO 11348-3:2007) to synthetic sea water (ISO 10253:2006) is proposed. The hormesis phenomenon was observed only during the analysis of wastewater toxicity with the standard toxicity test (with the diluent). The use of synthetic sea water eliminated the hormetic effects because of the presence of additional components in the sea water, such as MgCl₂, Na₂SO₄, CaCl₂, KCl, NaHCO₃, and H₃BO₃, which increased the sensitivity of A. fischeri to the pharmaceutical substances. The use of different media in toxicity tests may have significant effects on the toxicity classification of the tested compounds or wastewater. Additionally, the toxicity of tested pharmaceuticals towards A. fischeri was analysed. The IC₅₀ values of DCF were 8.7 ± 1.1 mg L^-1 (for diluent) and 13.9 ± 0.9 mg L^-1 (for synthetic sea water) whereas those of SMX were 50.5 ± 2.3 and 55.3 ± 1.6 mg L^-1, respectively.

Assessment of Biological Toxicity and Ecological Safety for Urban Black-Odor River Remediation

The judgment and assessment of remediation effect on urban black-odor river still depend on the physical-chemical parameters and lack in ecological safety effects. A set of combined biological toxicity tests were applied to evaluate the ecological effects of one urban black-odor river before and after the remediation. The special growth rate of Chlorella vulgaris and mortality rate of Daphnia magna were used to assess acute toxicity. The Salmonella Typhimurium/Reverse Mutation Assay was applied to test the mutagenicity. The tests by C. vulgaris growth showed that there was no inhibition before and after remediation by overlying water, in contrast promoted the growth of C. vulgaris. The tests by D. magna showed slight toxicity on site 3# before remediation and nontoxic after remediation. The mutagenicity of organic extracts from overlying water at all sampling sites were positive before remediation, but were eliminated after remediation except from 3 of 4 sites on TA98 strain. The addition of the liver microsomal S9 induced the positive mutagenicity on site 4# compared to S9 absence. The results clarified the applicable and the importance of the biological toxicity tests on assessing the remediation effect and potential ecological risk of urban black-odor river.

Probabilistic ecological risk assessment of heavy metals using the sensitivity of resident organisms in four Korean rivers

The environment has been continuously exposed to heavy metals by various routes, from both natural and artificial sources. In particular, heavy metals in water can affect aquatic organisms adversely, even at very low concentrations, and can lead to the disturbance of the ecosystem balance and biodiversity. Ecological risk assessments are conducted to protect the environment from such situations, primarily by deriving the predicted no-effect concentration (PNEC) from the species sensitivity distribution (SSD). This study developed the SSDs based on the species living in Korean freshwater for four heavy metals including cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). The species compositions of the SSDs were examined, and three types of PNECs were derived by applying different assessment factors (AF). In addition, the occurrence and concentrations of heavy metals in Korean rivers were investigated, and the ecological risk assessment was carried out to compare the SSDs with the environmental concentrations. The SSDs were developed using a sufficient number of species, but the missing data of plants and insects provided an incomplete species composition. The results show that Cd and Pb in the environmental concentrations of rivers would not cause any risk to aquatic organisms from the derived PNEC. However, some organisms might be adversely affected by the concentrations of Zn, and a small amount of risk was expected under the conservative PNEC. The distribution of Cu in the rivers was not considered to be safe for aquatic organisms because the average environmental concentrations potentially affected the proportion of the SSD, and the environmental concentrations exceeded the PNECs. The concentrations of Cu and Zn in industrial waters indicated a considerable risk to aquatic organisms, and the probability of exceeding the PNECs appeared to be quite high. Therefore, this study indicates that additional actions and parallel field studies are required based on the risk posed to aquatic organisms by Cu and Zn in four Korean rivers.

The analysis of the possibility of using biological tests for assessment of toxicity of leachate from an active municipal landfill

One of the consequence of municipal waste deposition is the production of landfill leachate. Its volume and composition is determined by numerous factors, including waste composition, landfill age and the volume of precipitation. Leachate may contain a number of mineral and organic compounds, the volume of which must be controlled regularly. One of the methods of determining the toxicity of substances contained in landfill leachate is the use of biological tests, based - among others - on aquatic organisms sensitive to environmental contamination. The purpose of this study was to analyse the possibility of using ecotoxicological tests (supplementing the physical and chemical tests) for the purpose of assessment of landfill leachate toxicity. The tests were conducted at an operating municipal landfill in Stary Sącz (southern Małopolska Region, Poland N: 49°55'33"76, E: 20°65'68'70) from December 2015 to October 2016. The scope of the tests included the analysis of physical and chemical indicators as part of the landfill monitoring process, and also the analysis of additional selected indicators: namely the boron, barium and vanadium content. The selected ecotoxicological tests included tests using Daphnia magna Straus (Cladocera, Crustacea). Leachate tests conducted with the use of physical and chemical indicators have, for nearly twenty years, mainly demonstrated changes related to the age of the used landfill; besides increased boron and barium values, no evident contamination has been found, excluding the case of boron. However, a statistically significant correlation between the B and Ba contents and the amount of precipitation was determined. In two cases, the used biological tests have confirmed the toxicity of the leachate: in January and June 2016. In the same months, the highest and abnormal boron contents were measured, which could cause a toxic effect of leachates.

Removal and transformation of benzotriazole in manganese-oxide biofilters with Mn(II) feeding

The aim of this study was to evaluate the treatment of organic-carbon-deficient wastewater containing benzotriazole (BTA) in lab-scale aerated biofilters filled with natural manganese oxide ore, sand coated with synthetic manganese oxides and sand (as a control material) in terms of BTA removal efficiency, its transformation products and ecotoxicological impact of the treated wastewater. Additionally, the effect of Mn(II) feeding was tested. The removal of BTA in all the biofilters was ≥97%. The contribution of the biotic removal of this compound was 15%, 50%, and 75% in the systems filled with sand, synthetic and natural manganese oxides, respectively. Only the columns filled with natural manganese oxides provided significant removal of DOC and decrease of UV₂₅₄ and SUVA₂₅₄, with even more pronounced effect with Mn(II) feeding. The presence of Mn(II) was also found to enhance the removal of NNH₄ in the systems filled with either form of manganese oxides, otherwise the removal of NNH₄ was negligible or negative. The transformation reactions of BTA were methylation, hydroxylation, and triazole ring cleavage. Based on the number of compounds and their relative abundance, the methylated transformation products were predominant in the effluent. The reduction of the ecotoxicity (Microtox bioassay) of the effluents was positively correlated with the decrease of UV₂₅₄, SUVA and DOC and only moderately with the removal of BTA. This study has shown that the natural manganese oxide ore provides the broadest set of services as a filtering material for aerated biofilters treating carbon-deficient wastewater containing BTA.

Validation of a biotic ligand model on site-specific copper toxicity to Daphnia magna in the Yeongsan River, Korea

The objective of this study was to determine whether the water effect ratio (WER) or biotic ligand model (BLM) could be applied to efficiently develop water quality criteria (WQC) in Korea. Samples were collected from 12 specific sites along the Yeongsan River (YSR), Korea, including two sewage treatment plants and one estuary lake. A copper toxicity test using Daphnia magna was performed to determine the WER and to compare to the BLM prediction. The results of the WER from YSR samples also indicated significantly different copper toxicities in all sites. The model-based predictions showed that effluent and estuary waters had significantly different properties in regard to their ability to be used to investigate water characteristics and copper toxicity. It was supposed that the slight water characteristics changes, such as pH, DOC, hardness, conductivity, among others, influence copper toxicity, and these variable effects on copper toxicity interacted with the water composition. The 38% prediction was outside of the validation range by a factor of two in all sites, showing a poor predictive ability, especially in STPs and streams adjacent to the estuary, while the measured toxicity was more stable. The samples that ranged from pH 7.3-7.7 generated stable predictions, while other samples, including those with lower and the higher pH values, led to more unstable predictions. The results also showed that the toxicity of Cu in sample waters to D. magna was closely proportional to the amounts of acidity, including the carboxylic and phenolic groups, as well as the DOC concentrations. Consequently, the acceptable prediction of metal toxicity in various water samples needs the site-specific results considering the water characteristics such as pH and DOC properties particularly in STPs and estuary regions.

Evaluation of toxic and genotoxic potential of a wet gas scrubber effluent obtained from wooden-based biomass furnaces: A case study in the red ceramic industry in southern Brazil

Red ceramic industry in southern Brazil commonly uses wood biomass as furnace fuel generating great amounts of gas emissions and ash. To avoid their impact on atmospheric environment, wet scrubbing is currently being applied in several plants. However, the water leachate formed could be potentially toxic and not managed as a common water-based effluent, since the resulting wastewater could carry many toxic compounds derived from wood pyrolysis. There is a lack of studies regarding this kind of effluent obtained specifically and strictly from wooden-based biomass furnaces. Therefore, we conducted an evaluation of toxic and genotoxic potentials of this particular type of wet gas scrubber effluent. Physical-chemical analysis showed high contents of several contaminants, including phenols, sulphates and ammoniacal nitrogen, as well as the total and suspended solids. The effluent cause significant toxicity towards microcrustacean Artemia sp. (LC50 = 34.4%) and Daphnia magna (Toxicity Factor = 6 on average) and to higher plants (Lactuca sativa L. and Allium cepa L.) with acute and sub-acute effects in several parameters. Besides, using plasmid DNA, significant damage was observed in concentrations 12.5% and higher. In cellular DNA, concentrations starting from 12.5% and 6.25% showed significant increase in Damage Index (DI) and Damage Frequency (DF), respectively. The results altogether suggest that the effluent components, such phenols, produced by wood combustion can be volatilized, water scrubbed, resulting in a toxic and genotoxic effluent which could contaminate the environment.

Water quality comparison of secondary effluent and reclaimed water to ambient river water of southern Okinawa Island via biological evaluation

The objective of this work was to evaluate the biological effect of the secondary effluent (SE) of a wastewater treatment plant and reclaimed water treated via ultrafiltration (UF) followed by either reverse osmosis (RO) membrane filtration or nanofiltration (NF) to be used for environmental use by comparing the results of algal growth inhibition tests of concentrated samples of the SE and permeates of RO and NF with those of six rivers in southern Okinawa Island. Although the SE water had no adverse effects on the growth of the algae Pseudokirchneriella subcapitata, it could lead to water quality degradation of rivers in terms of its toxic unit value, whereas the use of RO and NF permeates would not lead to such degradation. The recharge of rivers, into which domestic wastewater and livestock effluents might be discharged in southern Okinawa Island, with reclaimed water subjected to advanced treatment could dilute the concentrations of chemicals that cause biological effects and improve the water quality of the rivers, based on the results of the bioassay using P. subcapitata. Comparing the results of bioassays of reclaimed water with those of the ambient water at a site might be effective in assessing the water quality of reclaimed water for environmental use at the site.

Occurrence of pharmaceuticals in WWTP effluents and their impact in a karstic rural catchment of Eastern France

The occurrence of pharmaceuticals in freshwater ecosystems provokes increasing concern due to their potential risk to non-target organisms and to human health. Pharmaceuticals are used in both human and veterinary medicine and are essentially released into the environment via wastewater treatment plants (WWTPs) and from livestock. In this study, 31 pharmaceuticals were analyzed in effluent and surface water upstream and downstream of two WWTPs in the Loue-Doubs rural karstic catchment in Eastern France. Diclofenac (965 and 2476 ng L^-1), sulfamethoxazole (655 and 1380 ng L^-1) and carbamazepine (566 and 1007 ng L^-1) displayed the highest levels in the effluents of both WWTPs. Diclofenac levels were also high in surface water samples 300 and 166 ng L^-1 in the River Doubs and the River Loue, respectively, followed by paracetamol (273 and 158 ng L^-1) and sulfamethoxazole (126 and 73 ng L^-1). In both rivers, the most critical compounds were found to be the antibiotic sulfamethoxazole (risk quotient (RQ) from 23.7 to 51.1) and ofloxacine (RQ from 1.1 to 18.9), which reached levels inducing toxic effects in aquatic organisms. This study showed that WWTP effluents are the major sources of the pharmaceuticals, but raw discharges from human residences, pastures and livestock manure represent significant sources of contamination of surface water and groundwater. The aim of this study was to assist scientists and authorities in understanding occurrence and sources of pharmaceuticals in order to improve water quality management in chalk streams.

Novel test procedure to evaluate the treatability of wastewater with ozone

Organic micropollutants such as pharmaceuticals, estrogens or pesticides enter the environment continuously through the effluent of municipal wastewater treatment plants (WWTPs). Enhanced treatment of wastewater (WW) by ozone (O3) is probably one of the simplest measures for abatement of organic micropollutants to avoid their discharge to the aquatic environment. During ozonation most organic micropollutants present in treated WW are oxidized either by a direct reaction with O3 or by secondarily formed hydroxyl radicals (OH). However, undesired oxidation by-products from the oxidative transformation of matrix components can also be formed. A modular laboratory decision tool based on the findings of previous investigations is presented to test the feasibility of ozonation as an option to upgrade specific WWTPs. These modules consist of investigations to assess (i) the matrix effects on ozone stability, (ii) the efficiency of micropollutant removal, (iii) the oxidation by-product formation, as well as (iv) bioassays to measure specific and unspecific toxicity of the treated WWs. Matrix effects on ozone stability (quantified as O3 and OH exposures) can give first indications on the suitability of an ozonation step. Ozonation of WWs yielding O3 and OH exposures and micropollutant abatement similar to reference values evoked a significant improvement of the water quality as indicated by a broad range of bioassays. Irregular behavior of the ozonation points towards unknown compounds, possibly leading to the formation of undesired degradation products. It has been observed that in such WWs ozonation partly enhanced toxicity. In summary, the presented tiered laboratory test procedure represents a relatively cheap and straight-forward methodology to evaluate the feasibility of ozonation to upgrade specific WWTPs for micropollutant removal based on chemical and biological measurements.

Ecotoxicity assessment of artificial groundwater recharge with reclaimed water: a pilot-scale study

A demonstration of artificial groundwater recharge with tertiary effluent was evaluated using a set of bioassays (acute toxicity to Daphnia, genotoxicity, estrogenic and antiestrogenic toxicity). Around 95 % genotoxicity and 53 % antiestrogenicity were removed from the feed water by ozonation, whereas significant reduction of acute toxicity to Daphnia magna was achieved during a 3 days vadose soil treatment. The toxicity was further removed to the same level as the local groundwater during a 20 days aquifer soil treatment. The pilot study has shown that ozonation and soil treatments can improve the quality of municipal wastewater treatment plant effluents for possible groundwater recharge purposes.

Ecological risk assessment of on-site soil washing with iron(III) chloride in cadmium-contaminated paddy field

On-site soil washing with iron(III) chloride reduces Cd levels in soil, and thus the human health risks caused by Cd in food. However, it may threaten aquatic organisms when soil washing effluent is discharged to open aquatic systems. Therefore, we conducted trial-scale on-site soil washing and ecological risk assessment in Nagano and Niigata prefectures, Japan. The ecological effect of effluent water was investigated by two methods. The first was bioassay using standard aquatic test organisms. Twice-diluted effluent water from the Nagano site and the original effluent water from the Niigata site had no significant effects on green algae, water flea, caddisfly, and fish. The safe dilution rates were estimated as 20 times and 10 times for the Nagano and Niigata sites, respectively, considering an assessment factor of 10. The second method was probabilistic effect analysis using chemical analysis and the species sensitivity distribution concept. The mixture effects of CaCl(2), Al, Zn, and Mn were considered by applying a response additive model. The safe dilution rates, assessed for a potentially affected fraction of species of 5%, were 7.1 times and 23.6 times for the Nagano and Niigata sites, respectively. The actual dilution rates of effluent water by river water at the Nagano and Niigata sites were 2200-67,000 times and 1300-110,000 times, respectively. These are much larger than the safe dilution rates derived from the two approaches. Consequently, the ecological risk to aquatic organisms of soil washing is evaluated as being below the concern level.

Landfill leachate toxicity removal in combined treatment with municipal wastewater

Combined treatment of landfill leachate and municipal wastewater was performed in order to investigate the changes of leachate toxicity during biological treatment. Three laboratory A2O lab-scale reactors were operating under the same parameters (Q-8.5–10 L/d; HRT-1.4–1.6 d; MLSS 1.6–2.5 g/L) except for the influent characteristic and load. The influent of reactor I consisted of municipal wastewater amended with leachate from postclosure landfill; influent of reactor II consisted of leachate collected from transient landfill and municipal wastewater; reactor III served as a control and its influent consisted of municipal wastewater only. Toxicity of raw and treated wastewater was determinted by four acute toxicity tests with Daphnia magna, Thamnocephalus platyurus, Vibrio fischeri, and Raphidocelis subcapitata. Landfill leachate increased initial toxicity of wastewater. During biological treatment, significant decline of acute toxicity was observed, but still mixture of leachate and wastewater was harmful to all tested organisms.

Use of TIE techniques to characterize industrial effluents in the Pearl River Delta region

We investigated the acute toxicity of various industrial effluents in the Pearl River Delta region using lux bacteria, duckweed, green algae, crustaceans and zebrafish. The potential toxicants in the industrial effluents were identified and evaluated by lux bacteria bioassay and chemical analysis. The results show that green algae (Pseudokirchneriella subcapitata) and crustacean (Ceriodaphnia dubia) were more sensitive to the effluents from electronic and electroplate factories than other test species, while lux bacteria were more sensitive to all the other effluents. The toxicities of effluents from electronic and electroplate factories to the six test organisms were significantly higher than those of the other industrial effluents, and mainly caused by metals. Noticeably, organic pollutants were the main contributing factor to the toxicity of effluents from textile and dyeing plants, pulp and paper mills, fine chemical factories and municipal wastewater treatment plants.

Toxicity of raw and neutralized bauxite refinery residue liquors to the freshwater cladoceran Ceriodaphnia dubia and the marine amphipod Paracalliope australis

The extraction of alumina from bauxite produces a highly toxic residue, termed bauxite refinery residue (BRR) or red mud. The toxicity of this material is due to chemical and biological effects of high pH, alkalinity, electrical conductivity (EC), and Na(+) and Al(3+) concentrations. Several neutralization techniques may allow BRR to be used for environmental remediation. The present study investigated standardized 48-h acute toxicity tests with a freshwater cladoceran, Ceriodaphnia dubia, and a marine amphipod, Paracalliope australis, against raw supernatant BRR liquor (RL) versus liquors neutralized with acid (ANL), CO(2) (CNL), seawater (SNL), and a hybrid method (HNL). Based on 48-h LC50 values, the toxicity of the liquors to C. dubia increased in the following order; HNL ≤ SNL< ANL ≤ CNL < RL, with comparable responses from P. australis. The high toxicity of RL likely is due to high pH (≈ 12), alkalinity, and Al concentration. Toxicity of CNL likely is due to high EC and alkalinity. Sulfate and Na(+) concentrations are considered sources of toxicity in ANL. Seawater-neutralized liquor and HNL were considerably less toxic to both test species. These data provide evidence of the acute lethal toxicity of raw supernatant liquor from BRR and four neutralized supernatant liquors to the freshwater cladoceran C. dubia and the marine amphipod P. australis, providing valuable baselines for further ecotoxicological investigations of BRR materials in aquatic environments.

Acute toxicity of nitrite and ammonia to Daphnia similoides of different developmental stages: using the modified Gaussian model to describe

To gain an insight into the tolerance of Daphnia to nitrite and ammonia, a modified Gaussian model was used to describe the trends of changes in LC50s of nitrite and ammonia to Daphnia similoides at different developmental stages. LC50s of NO(2)-N and NH(3)-N increased with age before maturation and then decreased at maturation. A modified Gaussian model provided an accurate fit for the changes in LC50s of NO(2)-N and NH(3)-N, in which the parameters have definite biological meanings. From this model, we can gain an insight into the maximum LC50 and the age that has the maximum LC50 and predict LC50s at any specific ages. We suggest that such a model might be used to describe the trend in acute toxicity of some other zooplankton species at different stages.

The relationship between whole effluent toxicity (WET) and chemical-based effluent quality assessment in Vojvodina (Serbia)

The relationship between whole effluent toxicity (WET) and chemical-based effluent quality assessment across a range of effluent types was examined for the first time in Serbia. WET was determined by Daphnia magna acute tests, while chemical-based toxicity was taken as theoretical for concentrations of priority chemicals and effluent quality assessment based on the valid Serbian regulations. A poor correlation was found between WET and chemical-based effluent quality assessment: positive toxicity tests were found, in general, in cases where samples satisfied the requirements of mandatory effluent monitoring. Statistically insignificant correlation between the predicted and observed toxicity indicated that the presence of priority substances accounted to the overall toxicity only to a certain degree, most probably due to a rather short list of priority pollutants regularly analysed in effluents. Current monitoring requirements neglect hazards that derive from potentially present toxicants and unpredictable toxicity of complex mixtures, which led to poor correlation between the WET and chemical-based results in this study.