Tiered Approach for the Evaluation of Environmental Impacts of Triclosan on Aquatic Ecosystems

The synthetic broad-spectrum antibacterial agent triclosan is one of the most commonly encountered emerging micro-pollutant in the aquatic environment due to the extensive use since 1968 mainly in cosmetics and household cleaning products and the partial elimination from wastewater. Its low water solubility, high sorption coefficient to organic matter, accumulation potential in fatty tissues and its low acute toxicity determined by conventional ecotoxicological tests suggest that its risk is more related to chronic effects requiring risk assessment based on more sensitive ecotoxicological methods. In this paper the short- and midterm ecotoxicological effects of triclosan were investigated using various test systems taking into account ecological complexity and environmental relevance. Acute single-species, simplified microcosm experiments and complex multi-species microcosm experiments were conducted with the determination of sublethal physiological and behavioral endpoints including the Daphnia magna heartbeat rate and feeding activity, the Heterocypris incongruens movement parameters and the Lemna minor chlorophyll content and root length. All physiological and behavioral endpoints indicated sensitively the adverse effect of triclosan in the concentration range of 4–25.6 µg/L. In some cases, responses of selected organisms in single-species laboratory tests did not correspond to those of the higher levels of test systems. Daphnia sensitivity increased with the level of the test system for all chosen endpoints except the heartbeat rate. Considering the varying ecological complexity of the assembled test systems, according to our results the exposure time and the different combinations of exposure routes were the most decisive parameters in terms of triclosan ecotoxicity and endpoint sensitivity

The potential of Hungarian bauxite residue isolates for biotechnological applications

Bauxite residue (red mud) is considered an extremely alkaline and salty environment for the biota. We present the first attempt to isolate, identify and characterise microbes from Hungarian bauxite residues. Four identified bacterial strains belonged to the Bacilli class, one each to the Actinomycetia, Gammaproteobacteria, and Betaproteobacteria classes, and two to the Alphaproteobacteria class. All three identified fungi strains belonged to the Ascomycota division. Most strains tolerated pH 8–10 and salt content at 5–7% NaCl concentration. Alkalihalobacillus pseudofirmus BRHUB7 and Robertmurraya beringensis BRHUB9 can be considered halophilic and alkalitolerant. Priestia aryabhattai BRHUB2, Penicillium chrysogenum BRHUF1 and Aspergillus sp. BRHUF2 are halo- and alkalitolerant strains. Most strains produced siderophores and extracellular polymeric substances, could mobilise phosphorous, and were cellulose degraders. These strains and their enzymes are possible candidates for biotechnological applications in processes requiring extreme conditions, e.g. bioleaching of critical raw materials and rehabilitation of alkaline waste deposits

Ecotoxicity attenuation by acid-resistant nanofiltration in scandium recovery from TiO2 production waste

The lack of high-grade scandium (Sc) ores and recovery strategies has stimulated research on the exploitation of non-ore-related secondary sources that have great potential to safeguard the critical raw materials supply of the EU's economy. Waste materials may satisfy the growing global Sc demand, specifically residues from titanium dioxide (TiO2) production. New technologies are being developed for the recovery of Sc from such residues; however, the possible environmental impacts of intermediary products and residues are usually not considered. In order to provide a comprehensive ecotoxicity characterisation of the wastes and intermediate residues resulting from one promising new technology, acid-resistant nanofiltration (arNF), a waste-specific ecotoxicity toolkit was established. Three ecotoxicity assays were selected with specific test parameters providing the most diverse outcome for toxicity characterisation at different trophic levels: Aliivibrio fischeri (bacteria) bioluminescence inhibition (30 min exposure), Daphnia magna (crustacean) lethality and immobilisation (24 h exposure) and Lemna minor (plant) growth inhibition with determination of the frond number (7 d exposure). According to our results, the environmental impact of the generated intermediate and final residues on the aquatic ecosystem was mitigated by the consecutive steps of the filtration methods applied. High and statistically significant toxicity attenuation was achieved according to each test organism: toxicity was lowered based on EC20 values, according to the A. fischeri bioluminescence inhibition assay (by 97%), D. magna lethality (by 99%) and L. minor frond number (by 100%), respectively, after the final filtration step, nanofiltration, in comparison to the original waste. Our results underline the importance of assessing chemical technologies' ecotoxicological and environmental impacts with easy-to-apply and cost-effective test methods to showcase the best available technologies

Evaluation of a bioelectrochemical reductive/oxidative sequential process for chlorinated aliphatic hydrocarbons (CAHs) removal from a real contaminated groundwater

In the present study, the sequential reductive/oxidative bioelectrochemical process has been tested with real groundwater from a contaminated site in Northern Italy for chlorinated aliphatic hydrocarbons (CAHs) removal. The sequential system was developed by connecting in series two membrane-less microbial electrolysis cells (MECs) equipped with an internal graphite counter electrode. The first MEC aimed at the CAHs reductive dechlorination (RD) and was constituted of a granular graphite working electrode. In the second MEC, a mixed metal oxide working electrode stimulated the oxidative dechlorination of the low chlorinated RD's by-products through oxygen production. The sequential process allowed complete mineralization of the CAHs contained in the real groundwater. A complete reduction of the perchloroethylene into vinyl chloride (VC) was observed in the first MEC polarized at −450 mV vs SHE, while the resulting VC was oxidized with a 92 ± 2 % efficiency in the second MEC due to the HRT increment from 0.7 to 1.7 days. Biomarkers of the reductive (Dehalococcoides mccartyi 16S rRNA and reductive dehalogenase genes) and oxidative (etnE, etnC genes) dechlorination have been monitored in the two MECs along with the ecotoxicity tests. Overall, they provide information on the efficiency of the applied technology and allow to assess the potential adverse effects. According to the Tetrahymena pyriformis reproduction inhibition test and Panagrellus redivivus mortality tests, showed a significant ecotoxicity reduction with respect its initial inhibitory effect at the tested concentrations