How toxic is toxic? A proposal for wastewater toxicity hazard assessment

Removal of contaminants of emerging concern from the supernatant of anaerobically digested sludge by O3 and O3/H2O2: Ozone requirements, effects of the matrix, and toxicity

Digestate is a rich source of nutrients that can be applied in agricultural fields as fertilizer or irrigation water. However, most of the research about application of digestate have focused on its agronomic properties and neglected the potential harm of the presence of contaminants of emerging concern (CECs). Aadvanced oxidation processes (AOPs) have proved to be effective for removing these compounds from drinking water, yet there are some constrains to treat wastewater and digestate mainly due to their complex matrix. In this study, the feasibility to remove different CECs from digestate using O3 and O3/H2O2 was assessed, and the general effect of the matrix in the oxidation was explained. While the lab-scale ozonation provided an ozone dose of 1.49 mg O3/mg DOC in 5 h treatment, almost all the compounds were removed at a lower ozone dose of maximum 0.48 mg O3/mg DOC; only ibuprofen required a higher dose of 1.1 mg O3/mg DOC to be oxidized. The digestate matrix slowed down the kinetic ozonation rate to approximately 1% compared to the removal rate in demineralized water. The combined treatment (O3/H2O2) showed the additional contribution of H2O2 by decreasing the ozone demand by 59-75% for all the compounds. The acute toxicity of the digestate, measured by the inhibition of Vibrio fisheries luminescence, decreased by 18.1% during 5 h ozonation, and by 34% during 5 h O3/H2O2 treatment. Despite the high ozone consumption, the ozone dose (mg O3/mg DOC) required to remove all CECs from digestate supernatant was in the range or lower than what has been reported for other (waste-)water matrix, implying that ozonation can be considered as a post-AD treatment to produce cleaner stream for agricultural purposes.

Comprehensive study of acute toxicity using Microtox® bioassay in soils contaminated by lindane wastes

This research studies the acute toxicity of real contaminated soils (topsoil and subsoil) with hazardous chlorinated organic compounds (COCs) from lindane manufacturing wastes. The Microtox® bioassay was used to determine the toxicity of soils (modified Basic Solid Phase Test), soil elutriates (Basic Test), and organic extracts (adapted Organic Solvent Sample Solubilization Test), in which hydrophobic organic compounds are soluble. The acute toxicity of these persistent contaminants (hexachlorocyclohexanes, HCH isomers, as particulate matter in topsoil, and COCs, from dense non-aqueous phase liquid, DNAPL, in subsoil) and the commercial compounds were also measured. Soils tested showed different contaminant levels (topsoil: 0.9-1149 mg/kg and subsoil: 20-9528 mg/kg). Soil contaminants distribution, concentration and acute toxicity were highly related to the contamination source (HCHs or DNAPL). Soils, organic extracts, and subsoil elutriates presented high toxicity, highlighting the need for remediation of these sites. EC₅₀ was calculated in the three-test applied for the soils tested. EC₅₀ vs. COCs concentration in soils and soil elutriates showed an asymptotic trend, explained by the low pollutants solubility in the aqueous phase. Contrarily, EC₅₀ vs. soil COCs concentration was more linear in the case of the organic extracts. This test was the most reliable from statistical analysis. The three methods reveal interesting and complementary information and are necessary for a complete overview of the acute toxicity of contaminated soils.

Nature-based coagulants for drinking water treatment: An ecotoxicological overview

The intensive human activities extensively contaminated water sources making its treatment a problem of paramount importance, especially with the increasing of global population and water scarcity. The application of natural coagulants has become a promising and environmentally friendly alternative to conventional ones. This study was aimed at evaluating the efficiency of four plant extracts namely Agave americana, Carpobrotus acinaciformis, Austrocylindropuntia subulate, and Senicio anteuphorbium as natural coagulants to remove Microcystis aeruginosa cyanobacterium from water. The effects of pH (4, 5, 6, 7, 8 9, and 10) and coagulant dose (5, 10, 15, 20, 25, and 30 mg/L) on the coagulation efficiency were investigated. Results showed that plant-based extracts exhibited high coagulant abilities significantly contributing to the removal of M. aeruginosa cells up to 80% on a case-by-case basis. The ecotoxicity (Daphnia magna, Aliivibrio fischeri, Raphidocelis subcapitata, and Sorghum saccharatum) was absent or presented very slight acute toxicity up to 12.5 mg/L being S. anteuphorbium the least toxic. PRACTITIONER POINTS: Nature-based plant extracts showed removal rates up to 80%. Lower pH and A. subulate and S. anteuphorbium were the most efficient coagulants Toxicity effects were plant extracts-based and dose function. A. subulate and S. anteuphorbium were the least toxic extracts.

Degradation of metoprolol from wastewater in a bio-electro-Fenton system

Advanced oxidation processes (AOPs) have been intensely studied for the removal of refractory pollutants because of the strong oxidizing capacity of hydroxyl radical. One of the emerging AOP methods gaining increased attention is bio-electro-Fenton (BEF) which can generate hydroxyl radical in-situ in the cathode chamber using the energy harvested by exoelectrogenic bacteria in the anode. In this study, the feasibility of BEF technology for the removal of metoprolol, a typical micropollutant widely found in the water environment, was for the first time investigated. It was found that applied voltage and working pH had a significant effect on removal efficiency while Fe²⁺ dosage as catalyst showed a little effect. Besides removal by hydroxyl radical, metoprolol might be adsorbed on the surface of the reactor, electrode, and precipitated with iron sludge, especially at neutral pH. In a batch experiment with a supplied voltage of 0.2 V, pH 3, and a Fe²⁺ dose of 0.2 mM, the removal rate of metoprolol in the BEF for the synthetic wastewater and the real effluent from the secondary sediment tank was 66% and 55% within 12 h, respectively. A possible degradation pathway was proposed. Then the removal of metoprolol in a continuous flow BEF system was further studied at different hydraulic retention times (HRTs) of 2, 4, and 6 h, about 77%, 92%, and 95% removal was observed. A toxicity test (less than 20% inhibition on bioluminescence) during treatment and energy cost analysis (5.269 × 10^-3 kWh/order/m³) in treating 10 μg/L of metoprolol containing wastewater effluent at continuous flow mode implied that the proposed BEF has a potential for wastewater treatment.

An innovative microbial electrochemical ultraviolet photolysis cell (MEUC) for efficient degradation of carbamazepine

Discharge of recalcitrant pharmaceuticals into aquatic environments can lead to serious negative environmental effects. While traditional wastewater treatment plants (WWTPs) are efficient for a wide range of non-toxic pollutants (i.e. ammonia), some wastewater streams contain recalcitrant toxic trace micropollutants such as pharmaceuticals that cannot be removed by the treatment processes that are typically employed in common WWTPs. Herein, an innovative 20 L microbial electrochemical ultraviolet photolysis cell (MEUC) was developed for the first time by the integration of a UV irradiation and a bioelectrochemical system, which exhibited efficient treatment of carbamazepine-a model pharmaceutical compound. Notably, neither the UV irradiation nor the bioelectrochemical system alone could effectively eliminate carbamazepine. The effect of operational parameters including applied voltage, cathodic aeration rate, UV intensity, and hydraulic retention time were evaluated. The obtained results elucidated that the degradation of carbamazepine was consistent with pseudo-first-order reaction kinetics, and required a lower energy input than traditional advanced oxidation processes. Five main transformation products were identified, and probable transformation pathways were established. Furthermore, the eco-toxicity as tested by Vibrio fischeri showed no significant bioluminescence inhibition by the treated carbamazepine effluent. Finally, the MEUC system was further tested with a real wastewater matrix, which again exhibited effective removal of carbamazepine. This paper provides a proof-of-concept verification of the novel MEUC system, which contributes insight for the subsequent vigorous development of the application of such efficient and cost-effective technologies for the treatment of trace pharmaceuticals wastewater.

The fate of cigarette butts in different environments: Decay rate, chemical changes and ecotoxicity revealed by a 5-years decomposition experiment

Cigarette butts (CBs) are the most common litter item on Earth but no long-term studies evaluate their fate and ecological effects. Here, the role of nitrogen (N) availability and microbiome composition on CBs decomposition were investigated by a 5-years experiment carried out without soil, in park grassland and sand dune. During decomposition, CBs chemical changes was assessed by both ¹³C CPMAS NMR and LC-MS, physical structure by scanning electron microscope and ecotoxicity by Aliivibrio fischeri and Raphidocelis subcapitata. Microbiota was investigated by high-throughput sequencing of bacterial and eukaryotic rRNA gene markers. CBs followed a three-step decomposition process: at the early stage (∼30 days) CBs lost ∼15.2% of their mass. During the subsequent two years CBs decomposed very slowly, taking thereafter different trajectories depending on N availability and microbiome composition. Without soil CBs showed minor chemical and morphological changes. Over grassland soil a consistent N transfer occurs that, after de-acetylation, promote CBs transformation into an amorphous material rich in aliphatic compounds. In sand dune we found a rich fungal microbiota able to decompose CBs, even before the occurrence of de-acetylation. CBs ecotoxicity was highest immediately after smoking. However, for R. subcapitata toxicity remained high after two and five years of decomposition.

Ecotoxicological assessment of bauxite residue (red mud) overflow treated by dissolved air flotation (DAF)

In this study, the effluent from the Bayer process of transforming bauxite into alumina, followed by dissolved air flotation (DAF) treatment, was evaluated to identify the best experimental conditions that generate less toxic or nontoxic effluent for discharge. Two freshwater organisms, the Chlorophyceae microalga Raphidocelis subcapitata (96-h algal growth inhibition test), and the microcrustacean Daphnia similis (48-h acute immobility test), were used to analyze the efficiency of effluent treatment by detecting and comparing the toxicity of the treated effluent. Experimental factorial planning used different concentrations of the coagulant ferric chloride and the flocculant Nalco® N-99-005B, and different recycle ratios. The highest recycle ratio (30%) and highest flocculant concentration (150 mg/L) had the best solids removal efficiency, above 90%. Probably the higher concentration of flocculant led to the formation of a more stable froth, promoting an increase in the hydrophobic characteristics of the flocs. Two operating conditions were satisfactory according to acute and chronic bioassays, with removal efficiencies of total suspended solids and turbidity higher than 98%, for both variables. Producers, R. subcapitata microalga, were more sensitive than the primary consumers, D. similis microcrustaceans, indicating the importance of performing tests with different bioindicators.

Characterization of Miscellaneous Effluent Discharges from a Mobile Offshore Drilling Unit to the Marine Environment

A study was performed to evaluate the potential biological impacts from 8 different miscellaneous discharges from an oil and gas mobile offshore drilling unit (MODU) including deck drainage, desalination unit waste, boiler blowdown, fire control system test water, noncontact cooling water, and bilge water. Samples were evaluated for toxicity using a rapid (<1 h) initial screening test (echinoderm [Dendraster excentricus] fertilization test), and if toxicity was found, further testing was conducted using 3 chronic whole-effluent toxicity tests. This additional testing included the embryo larval development 72-h echinoderm (D. excentricus); 7-d mysid (Americamysis bahia) survival, growth, and fecundity invertebrate test; and 7-d topsmelt (Atherinops affinis) survival and growth fish test. Toxicity identification evaluations were performed on 3 discharges that consistently elicited a toxic response during whole-effluent toxicity testing. To place the results of the toxicity testing into the context of environmental risk, the spatial extent of potential biological effects was investigated using the CORMIX mixing zone model. The output of the modeling indicated that discharge of selected effluents did not result in concentrations, or duration of exposure, that would elicit toxic effects to organisms living in the surrounding environment. The present study provides a comprehensive data set that was used to characterize potential toxicity and environmental risk of MODU "miscellaneous discharges" which could help inform future risk assessments of these discharges. Environ Toxicol Chem 2019;38:2811-2823. © 2019 SETAC.

Municipal wastewater spiramycin removal by conventional treatments and heterogeneous photocatalysis

This study assessed the effects and removal options of the macrolide spiramycin, currently used for both in human and veterinary medicine- with a special focus on advanced oxidation processes based on heterogeneous TiO₂^_assisted photocatalysis. Spiramycin real concentrations were investigated on a seasonal basis in a municipal wastewater treatment plant (up to 35μgL^-1), while its removal kinetics were studied considering both aqueous solutions and real wastewater samples, including by-products toxicity assessment. High variability of spiramycin removal by activated sludge treatments (from 9% (wintertime) to >99.9% (summertime)) was observed on a seasonal basis. Preliminary results showed that a total spiramycin removal (>99.9%) is achieved with 0.1gL^-1 of TiO₂ in aqueous solution after 80min. Integrated toxicity showed residual slight acute effects in the photocatalytic treated solutions, independently from the amount of TiO₂ used, and could be linked to the presence of intermediate compounds. Photolysis of wastewater samples collected after activated sludge treatment during summer season (SPY 5μgL^-1) allowed a full SPY removal after 80min. When photocatalysis with 0.1gL^-1 of TiO₂ was carried out in wastewater samples collected in winter season (SPY 30μgL^-1) after AS treatment, SPY removal was up to 91% after 80min.

Bioavailability and toxicity of trace metals (Cd, Cr, Cu, Ni, and Zn) in sediment cores from the Shima River, South China

Five sediment cores (S1-S5) were collected from the Shima River to determine the bioavailability of trace metals (Cd, Cr, Cu, Ni, and Zn) using the modified European Community Bureau of Reference (BCR) procedure. The toxic effects of polluted sediment were assessed using the LUMISTox^® bioassay with Vibrio fischeri and chemical models such as the toxicity unit (TU) of each metal, sum of all TUs (∑TU), and toxic risk index (TRI). The results showed that Cd, Ni, and Zn were present mainly in the acid-soluble and residual fractions, and the residual fraction of Cr accounted for the majority of the metal content (44%), while Cu was present mainly in the reducible and residual fractions. Cd had a mean enrichment factor (EF) of 15.1 and was considered to be severely enriched, while there was a minor enrichment of Cr and moderately severe enrichment of Zn, Cu, and Ni. From the LUMISTox^® bioassay, an acute TU (TUa) value exceeding 0.4 was found at the upper and middle reach sites and was considered to represent slightly acute toxicity, whereas little acute toxicity was found at the lower reach site. The acid-soluble fraction of trace metals was the geochemical fraction mainly responsible for the acute toxicity of the sediment, and acid-soluble Zn and Ni were identified as important contributors to sediment toxicity.

Combined effects of arsenic, salinity and temperature on Crassostrea gigas embryotoxicity

The combined effects of different salinity and temperature levels on the toxicity of Arsenic (As) were studied on the embryonic development of the oyster Crassostrea gigas. A standardized embryotoxicity test was performed to assess the interactive effects of these stressors, in a full factorial design experiment including a range of salinities (15, 19, 24, 28 and 32), temperatures (16, 20, 24, 28 and 32°C) and As concentrations (100, 300, 600, 1200, 2400µgL^-1). The embryotoxicity endpoint was about the determination of normal larvae development rates at various conditions, and median effect concentration (EC₅₀) determination for each As exposure condition. Results showed that toxicity induced by As was characterized by retardation of embryonic development observing toxic effects at lower concentrations than previously reported studies. The presence of As in seawater resulted in a narrower range of tolerance to both salinity and temperature. These findings bring new insights on the impacts of a common contaminant on an important shellfish species having a planktonic early life stage development, with potential implications for population survival and ecosystem functioning in a changing environment.

Combination of nanofiltration and ozonation for the remediation of real municipal wastewater effluents: Acute and chronic toxicity assessment

The purpose of this work was to study the ozonation of nanofiltration (NF) retentates of real municipal wastewater treatment plant (MWTP) effluents for removal of microcontaminants (MCs) and toxicity. MCs present in these effluents were monitored using LC-MS/MS. Acute and chronic toxicity was addressed with Daphnia magna, Vibrio fischeri and Selenastrum capricornutum. Up to 40 MCs were found, most of them in concentrations over 100ng/L. 90% degradation of the sum of MCs was the critical point of comparison. When the NF membrane system was applied to MWTP effluents, treatment of NF rejection needed 2.75-4.5g O₃/m³,4.5g O₃/m³, which is less than 50% of the ozone needed for direct treatment of MWTP effluent. Treatment time (lower than 11min) was not influenced by MCs concentration, at least in the range tested (25-190μg/L). It has been demonstrated that consumption of ozone increased with organic load and inorganic content of different real effluents. MCs were eliminated by ozonation but acute toxicity (against V. fischeri and D. magna) increased. Chronic toxicity results were different and contrary in D. magna and S. capricornutum, due to the generation of new transformation products more toxic to D. magna than the parent contaminants. S. capricornutum inhibition percentage decreased in all cases after ozonation treatment. According to these results, before ozonation is implemented in MWTPs for the removal of MCs, the transformation products must first be examined and the treatment time or ozone doses should be extended to complete degradation if necessary.

In situ remediation of contaminated marinesediment: an overview

Sediment tends to accumulate inorganic and persistent hydrophobic organic contaminants representing one of the main sinks and sources of pollution. Generally, contaminated sediment poses medium- and long-term risks to humans and ecosystem health; dredging activities or natural resuspension phenomena (i.e., strongly adverse weather conditions) can remobilize pollution releasing it into the water column. Thus, ex situ traditional remediation activities (i.e., dredging) can be hazardous compared to in situ techniques that try to keep to a minimum sediment mobilization, unless dredging is compulsory to reach a desired bathymetric level. We reviewed in situ physico-chemical (i.e., active mixing and thin capping, solidification/stabilization, chemical oxidation, dechlorination, electrokinetic separation, and sediment flushing) and bio-assisted treatments, including hybrid solutions (i.e., nanocomposite reactive capping, bioreactive capping, microbial electrochemical technologies). We found that significant gaps still remain into the knowledge about the application of in situ contaminated sediment remediation techniques from the technical and the practical viewpoint. Only activated carbon-based technologies are well developed and currently applied with several available case studies. The environmental implication of in situ remediation technologies was only shortly investigated on a long-term basis after its application, so it is not clear how they can really perform.

Evaluation of a battery of marine species-based bioassays against raw and treated municipal wastewaters

The present study evaluates a battery of marine species-based bioassays against chemically characterized municipal wastewater samples (raw and WWTP treated). We estimated Dunaliella tertiolecta growth rate inhibition (24-96h IC₅₀ values), Artemia franciscana immobilization (24h LC₅₀ values), mussel hemocytes viability and lipid peroxidation enhancement (in terms of neutral red retention assay/NRRT and malondialdehyde/MDA content, respectively) in influent- and WWTP effluent-treated species. We found algal growth arrest and stimulation respectively, almost similar 24hLC₅₀ values in Artemia sp., and significantly higher adverse effects (in terms of NRRT and MDA levels) in influent-treated mussel hemocytes. Furthermore, the estimation of hatchability, yolk-sac larvae mortality (24-120hLC₅₀) and spinal deformities (SD) in sea bream Sparus aurata showed slight variations over time, with the lowest LC₅₀ and SD₅₀ (representing spinal deformities at 50% of yolk-sac larvae) values to be observed in influent-treated larvae at 120h. Data interpretation (both chemical and biological) revealed that toxic endpoints, such as NRRT₅₀, 96hIC₅₀Dun, 120hLC₅₀Sparus and 120hSD₅₀Sparus, significantly related to WWTP removal efficiency and further mediated by the presence of dominant compounds, such as As and Cr, could be used for identifying main components of toxicity in wastewaters.

Effects of mineral amendments on trace elements leaching from pre-treated marine sediment after simulated rainfall events

Bauxite extraction by-products (red mud) were used to evaluate their potential ability to stabilize trace elements from dredged and aerated/humidified marine sediment. The investigated by-products were: bauxaline^®(BX) that is a press-filtered red mud; bauxsol™(BS) that is a press-filtered red mud previously washed with excess of seawater, and gypsum neutralized bauxaline^® (GBX). These materials were separately mixed to dredged composted sediment sample considering 5% and 20% sediment: stabilizer ratios. For pilot experiments, rainfall events were regularly simulated for 3 months. Concentrations of As, Mo, Cd, Cr, Zn, Cu, and Ni were analyzed in collected leachates as well as toxicity. Results showed that Cd, Mo, Zn, and Cu were efficiently stabilized in the solid matrix when 20% of BX, BS, and GBX was applied. Consequently, toxicity of leachates was lower than for the untreated sediment, meaning that contaminants mobility was reduced. A 5% GBX was also efficient for Mo, Zn and Cu stabilization. In all scenarios, As stabilization was not improved. Compared to all other monitored elements, Mo mobility seemed to depend upon temperature-humidity conditions during pilot experiments suggesting the need of further investigations.

Emerging Concern from Short-Term Textile Leaching: A Preliminary Ecotoxicological Survey

Textile dyes and their residues gained growing attention worldwide. Textile industry is a strong water consumer potentially releasing xenobiotics from washing and rinsing procedures during finishing processes. On a decentralised basis, also final consumers generate textile waste streams. Thus, a procedure simulating home washing with tap water screened cotton textiles leachates (n = 28) considering physico-chemical (COD, BOD₅, and UV absorbance) and ecotoxicological data (Daphnia magna, Pseudokirchneriella subcapitata and Lepidium sativum). Results evidenced that: (i) leachates presented low biodegradability levels; (ii) toxicity in more than half leachates presented slight acute or acute effects; (iii) the remaining leachates presented "no effect" suggesting the use of green dyes/additives, and/or well established finishing processes; (iv) no specific correlations were found between traditional physico-chemical and ecotoxicological data. Further investigations will be necessary to identify textile residues, and their potential interactions with simulated human sweat in order to evidence potential adverse effects on human health.

Study on wastewater toxicity using ToxTrak™ method

ToxTrak™ method is an analytical tool for the measurement of toxicity of drinking water, wastewater and natural water. It is based upon the estimation of the inhibitive effect on bacterial respiration processes. The main aim of this work was to test the applicability of ToxTrak™ method in the assessment of wastewater toxicity in a full-scale WWTP in Poland. In order to achieve it, the study was divided into two parts. First, the validation of ToxTrak™ method was performed. Second, wastewater toxicity was monitored in the long- and short-term campaigns. Validation of ToxTrak™ method revealed that the indigenous biomass (mixed cultures of activated sludge microorganisms) was more sensitive than Escherichia coli for both materials (wastewater and phenol) tested. The values of degree of inhibition determined for phenol towards indigenous biomass and E. coli were close to each other, and no statistically significant difference between them was found. It confirmed the reliability of the results obtained with the help of ToxTrak™ test. The toxicity of the effluent was always lower than that of the influent and the linear correlation between them was found. Despite, the decrease of wastewater toxicity in the WWTP, the effluents were ranked as toxic or highly toxic according to the classification of wastewater based upon the acute toxicity.

Metals and tributyltin sediment contamination along the Southeastern Tyrrhenian Sea coast

Anthropogenic pressures can adversely affect the quality of coastal sediment posing at risk human health and the ecosystem. The Southeastern Tyrrhenian Sea (STS) coast (Italy) is still largely unexplored under this point of view. This study investigated for the first time in the area the seasonal variation and potential impact of selected metals (Cd, Cr, Cu, Ni, and Pb) and tributyltin (TBT) from sediment samples collected along the STS coast (Casalvelino Marina, Casalvelino Bay, Acciaroli Marina and Acciaroli Bay) in the perspective of Water Framework Directive and Marine Strategy Framework Directive. Data were compared to the contamination background levels of Punta Licosa reference site considering elemental enrichment factors (EFs) and single substance- and mixture-based risk characterisation ratios. Further, data were discussed considering the review of Southern Tyrrhenian Sea sediment quality. Results evidenced an increase of contamination levels from March to October showing that marinas are more impacted than bays. Sediment EFs highlighted that contamination levels were always greater than the reference site like risk characterisation ratios, suggesting the presence of potential threats. The sediment quality database generated after literature review revealed a similar situation for the whole Southern Tyrrhenian Sea.

Photocatalytic degradation of the antibiotic chloramphenicol and effluent toxicity effects

Chloramphenicol sodium succinate (CAP, C15H15Cl2N2 Na2O8) is a broad-spectrum antibiotic exhibiting activity against both Gram-positive and Gram-negative bacteria as well as other groups of microorganisms only partially removed by conventional activated sludge wastewater treatment plants. Thus, CAP and its metabolites can be found in effluents. The present work deals with the photocatalytic degradation of CAP using TiO2 as photocatalyst. We investigated the optimization of reaction contact time and concentration of TiO2 considering CAP and its by-products removal as well as effluent ecotoxicity elimination. Considering a CAP real concentration of 25mgL(-1), kinetic degradation curves were determined at 0.1, 0.2, 0.4, 0.8, 1.6 and 3.2gL(-1) TiO2 after 5, 10, 30, 60 and 120min reaction time. Treated samples were checked for the presence of by-products and residual toxicity (V. fischeri, P. subcapitata, L. sativum and D. magna). Results evidenced that the best combination for CAP and its by-products removal could be set at 1.6gL(-1) of TiO2 for 120min with an average residual toxicity of approximately 10%, that is the threshold set for negative controls in most toxicity tests for blank and general toxicity test acceptability.

Assessment of sediment toxicity in the Lagoon of Venice (Italy) using a multi-species set of bioassays

Within the framework of a Weight of Evidence (WoE) approach, a set of four toxicity bioassays involving the amphipod Corophium volutator (10 d lethality test on whole sediment), the sea urchin Paracentrotus lividus (fertilization and embryo toxicity tests on elutriate) and the pacific oyster Crassostrea gigas (embryo toxicity test on elutriate) was applied to sediments from 10 sampling sites of the Venice Lagoon (Italy). Sediments were collected during three campaigns carried out in May 2004 (spring campaign), October 2004 (autumn campaign) and February 2005 (winter campaign). Toxicity tests were performed on all sediment samples. Sediment grain-size and chemistry were measured during spring and autumn campaigns. This research investigated (i) the ability of toxicity tests in discriminating among sites with different contamination level, (ii) the occurrence of a gradient of effect among sampling sites, (iii) the possible correlation among toxicity tests, sediment chemistry, grain size and organic carbon, and (iv) the possible occurrence of toxicity seasonal variability. Sediment contamination levels were from low to moderate. No acute toxicity toward amphipods was observed, while sea urchin fertilization was affected only in few sites in just a single campaign. Short-term effects on larval development of sea urchin and oyster evidenced a clear spatial trend among sites, with increasing effects along the axis connecting the sea-inlets with the industrial area. The set of bioassays allowed the identification of a spatial gradient of effect, with decreasing toxicity from the industrial area toward the sea-inlets. Multivariate data analysis showed that the malformations of oyster embryos were significantly correlated to the industrial contamination (metals, polynuclear aromatic hydrocarbons, hexachlorobenzene and polychlorinated biphenyls), while sea urchin development to sediment concentrations of As, Cr and organic carbon. Both embryo toxicity tests were significantly affected by high ammonia concentrations found in the elutriates extracted from some mudflat and industrial sediments. No significant temporal variation of the toxicity was observed within the experimental period. Amendments to the set of bioassays, with inclusion of chronic tests, can certainly provide more reliability and consistency to the characterization of the (possible) toxic effects.

Evaluation of an eventual ecotoxicity induced by textile effluents using a battery of biotests

Textile industry is considered as one of the important factors of the economic growth in Tunisia. However, this prominent role has certainly some drawbacks mainly represented by the huge amounts of textile wastewaters generated that become a real menace to nature. Many previous studies showed the purifying potential of some activated sludge and bacteria (Pseudomonas putida) to decolourize textile effluents. However, in many cases, decolourization of wastewaters is not necessary associated with detoxification, generating a real risk for the ecosystem in general. We evaluated in this work the induced toxicity of a textile effluent before and after its treatment with activated sludge followed by P. putida, using a battery of biotests. This study proved the detoxifying power of the activated sludge according to most of ecotoxicity tests. The treatment with P. putida did not improve the quality of the effluent; on the contrary, it could increase its toxicity. Daphnia magna and Raphidocelis subcapitata appear to be the most sensitive organisms in assessing eventual toxicity caused by this kind of wastewaters.

Distribution, migration and potential risk of heavy metals in the Shima River catchment area, South China

The distribution, migration and potential risk of heavy metals in water and soil environments, related to city water supply, were investigated. Heavy metal concentrations in waters from the Shima River water ranged from not detected (n.d.) to 749 μg L(-1) for Mn, n.d. to 151 μg L(-1) for Ni, 7.00 to 494 μg L(-1) for Zn, n.d. to 93.0 μg L(-1) for Cu and n.d. to 9860 μg L(-1) for Fe. The highest concentration of heavy metals was found at an upstream site in February as a result of industrial effluent discharge. Groundwater (GW1-GW5) and soil (S1-S8) samples along the riverbank showed similar levels of contamination due to a close hydraulic relationship and frequent exchange of water, probably resulting in migration of heavy metals from river water to the aquifer and accumulation at the interface. The mean concentrations of heavy metals in soil profiles were in the ranges of 2.50-19.0 mg kg(-1) for As, 2.80-11.2 mg kg(-1) for Cd, 20.3-165 mg kg(-1) for Cr, 14.5-298 mg kg(-1) for Cu, 11.4-102 mg kg(-1) for Ni, 7.00-95.0 mg kg(-1) for Pb, 40.4-465 mg kg(-1) for Zn, 8.80 × 10(3)-21.8 × 10(3) mg kg(-1) for Fe, and 62.2-430 mg kg(-1) for Mn, showing severe soil pollution by Cd. LUMISTox testing and the potential ecological risk index (RI) were used to assess the potential for adverse ecological effects caused by heavy metals in water and soil media. River water samples posed slight acute toxicity to Vibrio fischeri with luminescence inhibition rates (LIRs) ranging from 24.6% to 38.4% in February. Elevated Zn and Cu concentrations significantly contributed to the toxicity. However, groundwater did not exhibit any toxicity to Vibrio fischeri. The severity of the potential ecological risk for individual metals (Er(i)) decreased in the order of Cd > Cu > Ni > As > Pb > Zn > Cr. RI values indicated that all soil samples in the study area posed a high level of ecological risk. Cd contributed significantly (95.5-98.9%) to potential ecological risk in soils.

Which lesson can be learnt from a historical contamination analysis of the most polluted river in Europe?

The Sarno River trend analysis during the last 60 years was traced focusing on the socio-economic and environmental issues. The river, originally worshiped as a god by Romans, is affected by an extreme level of environmental degradation, being sadly reputed as the most polluted river in Europe. This is the "not to be followed" example of the worst way a European river can be managed. Data about water, sediment, soil, biota and air contamination were collected from scientific papers, monitoring surveys, and technical reports depicting a sick river. Originally, the river was reputed as a source of livelihood, now it is considered a direct threat for human health. Wastewater can still flow through the river partially or completely untreated, waste production associated with the manufacture of metal products and leather tanning continues to suffer from the historical inadequacy of regional wastewater treatment plants (WWTPs), associated with the partial or no reuse of effluents. All efforts should be devoted to solving the lack of wastewater and waste management, the gap in land planning, improving the capacity of existing WWTPs also via the construction of new sewer sections, restoring Sarno River minimum vital-flow, keeping to a minimum uncontrolled discharges as well as supporting river contracts. The 2015 goal stated by the Water Framework Directive (2000/60/EC) is still far to be reached. The lesson has not been learnt yet.

A toxicity scoring system for the 10-day whole sediment test with Corophium insidiosum (Crawford)

This study developed a tool able to evaluate the potential contamination of marine sediments detecting the presence or absence of toxicity supporting environmental decision-making processes. When the sample is toxic, it is important to classify its level of toxicity to understand its subsequent effects and management practices. Corophium insidiosum is a widespread and frequently recorded species along the Mediterranean Sea, North Sea and western Baltic Sea with records also in the Atlantic Ocean and Pacific Ocean. This amphipod is found in high abundance in shallow brackish inshore areas and estuaries also with high turbidity. At Italian level, C. insidiosum is more frequently collectable than Corophium orientale, making routine toxicity tests easier to be performed. Moreover, according to the international scientific literature, C. insidiosum is more sensitive than C. orientale. Whole sediment toxicity data (10 days) with C. insidiosum were organised in a species-specific toxicity score on the basis of the minimum significance difference (MSD) approach. Thresholds to rank samples as non-toxic and toxic were based on sediment samples (n=84) from the Gulf of Taranto (Italy). A five-class toxicity score (absent, low, medium, high and very high toxicity) was developed, considering the distribution of the 90th percentile of the MSD normalised to the effects on the negative controls (samples from reference sites). This toxicity score could be useful for interpreting sediment potential impacts and providing quick responsive management information.

Ecotoxicological evaluation of selected pharmaceuticals to Vibrio fischeri and Daphnia magna before and after photooxidation process

The aim of the research was the determination of the toxicity of photocatalytically treated water contaminated by different pharmaceuticals: chloramphenicol (CPL), diclofenac (DCF) or metoprolol (MT). Daphtoxkit F™ with Dapnia magna and Microtox(®) with Vibrio fischeri were used to evaluate the toxicity of the water before and after treatment. D. magna showed higher sensitivity to the presence of pharmaceuticals than V. fischeri. Generally, both tested organisms revealed the greatest sensitivity to the presence of CPL. The application of photocatalytic oxidation has resulted in decreased toxicity. It may confirm the reduction of high toxic parent compounds to less toxic metabolites. The toxicity was reduced in the range from 30% to 100% depending on pharmaceutical tested. The highest reduction of toxicity to V. fischeri and D. magna was observed to MT and CPL respectively. Depending on bioassay the toxicity decrease as follows: CPL>DCF>MT for D. magna and CPL>MT>DCF for V. fischeri.

Embryotoxicity of TiO2 nanoparticles to Mytilus galloprovincialis (Lmk)

Few data exist on the ecotoxicological effects of nanosized titanium dioxide (nTiO2) towards marine species with specific reference to bivalve molluscs and their relative life stages. Mytilus galloprovincialis Lamarck was selected to assess the potential adverse effects of nTiO2 (0-64 mg/L) on its early larval development stages (pre-D shell stage, malformed D-shell stage and normal D-shell stage larvae) considering two exposure scenarios characterised by total darkness (ASTM protocol) and natural photoperiod (light/dark). This approach was considered to check the presence of potential effects associated to the photocatalytic properties of nTiO2. Parallel experiments were carried on with the bulk reference TiCl4. The toxicity of nTiO2 showed to be mainly related to its "nano" condition and to be influenced by the exposure to light that supported the increase in the number of pre-D shell stage (retarded) larvae compared to the malformed ones especially at the maximum effect concentrations (4 and 8 mg nTiO2/L). The non-linear regression toxicity data analysis showed the presence of two EC50 values per exposure scenario: a) EC(50)1 = 1.23 mg/L (0.00-4.15 mg/L) and EC(50)2 = 38.56 mg/L (35.64-41.47 mg/L) for the dark exposure conditions; b) EC(50)1 = 1.65 mg/L (0.00-4.74 mg/L) and EC(50)2 = 16.39 mg/L (13.31-19.48 mg/L) for the light/dark exposure conditions. The potential implication of agglomeration and sedimentation phenomena on ecotoxicological data was discussed.

Ecotoxicological assessment and evaluation of a pine bark biosorbent treatment of five landfill leachates

When selecting a landfill leachate treatment method the contaminant composition of the leachate should be considered in order to obtain the most cost-effective treatment option. In this study the filter material pine bark was evaluated as a treatment for five landfill leachates originating from different cells of the same landfill in Sweden. The objective of the study was to determine the uptake, or release, of metals and dissolved organic carbon (DOC) during a leaching test using the pine bark filter material with the five different landfill leachates. Furthermore the change of toxicity after treatment was studied using a battery of aquatic bioassays assessing luminescent bacteria (Vibrio fischeri) acute toxicity (30-min Microtox®), immobility of the crustacean Daphnia magna, growth inhibition of the algae Pseudokirchneriella subcapitata and the aquatic plant Lemna minor; and genotoxicity with the bacterial Umu-C assay. The results from the toxicity tests and the chemical analysis were analyzed in a Principal Component Analysis and the toxicity of the samples before and after treatment was evaluated in a toxicity classification. The pine bark filter material reduced the concentrations of metal contaminants from the landfill leachates in the study, with some exceptions for Cu and Cd. The Zn uptake of the filter was high for heavily contaminated leachates (≥73%), although some desorption of zinc occurred in less contaminated waters. Some of the leachates may require further treatment due to discharge into a natural recipient in order to reduce the risk of possible biological effects. The difference in pH changes between the different leachates was probably due to variations in buffering capacity, affected by physicochemical properties of the leachate. The greatest desorption of phenol during filtration occurred in leachates with high conductivity or elevated levels of metals or salts. Generally, the toxicity classification of the leachates implies that although filter treatment with pine bark removes metal contaminants from the leachates effectively, it does not alter leachate toxicity noticeably. The leachates with the highest conductivity, pH and metal concentrations are most strongly correlated with an increased toxic response in the score plots of both untreated and treated leachates. This is in line with the toxicity classification of the leachate samples. The results from this study highlight the importance of evaluating treatment efficiency from the perspective of potential recipient effects, rather than in terms of residual concentrations of individual contaminants when treating waters with a complex contamination matrix, such as landfill leachates.

Toxicity removal efficiency of decentralised sequencing batch reactor and ultra-filtration membrane bioreactors

As a consequence of the Water Framework Directive and Marine Strategy Framework Directive, there is now more focus on discharges from wastewater treatment plants both to transitional and marine-coastal waters. The constraint to encourage sustainable water policy to prevent water deterioration and reduce or stop discharges has entailed new requirements for existing wastewater treatment plants in the form of advanced wastewater treatment technologies as further suggested by the Integrated Pollution and Prevention Control Bureau. A whole toolbox of physico-chemical and ecotoxicological parameters to investigate commercial and mixed domestic and industrial discharges was considered to check the efficiency of an Activated-Sludge Sequencing Batch Reactor (AS-SBR) and two Ultra-Filtration Membrane Biological Reactors (UF-MBRs) on a small scale decentralised basis. All discharges were conveyed into Venice lagoon (Italy), one of the widest impacted Mediterranean transitional environment. The UF-MBRs were able to provide good quality effluents potentially suitable for non-potable reuse, as well as reducing specific inorganic micro-pollutants concentration (e.g. metals). Conversely, the AS-SBR showed unpredictable and discontinuous removal abilities.