Luís Manuel Silva

Ecotoxicity tests in the environmental analysis of wastewater treatment plants: case study in Portugal.

A global evaluation of wastewaters should include ecotoxicological tests to complement the chemical characterization, with advantages especially in the case of complex wastewaters. A European project developed in Trancão River Basin (Portugal), integrated the ecotoxicological and physicochemical studies of wastewater samples from two municipal sewer networks and respective wastewater treatment plants. Wastewater samples were analysed for physicochemical parameters, ecotoxicological acute and chronic tests performed and the potential for endocrine disruption evaluated. Organic load parameters and total suspended solids showed significant correlations with Microtox and ThamnoToxKit test results. Data analysis showed that treated treatment plant effluent samples are associated with less organic contamination and less toxicity in ThamnoToxKit test. Chronic toxicity test and endocrine disruption assay of treatment plant effluent samples indicated that, in a long term, potential population effects could arise in the receiving waters. A test battery to monitor this type of wastewaters is proposed, including tests with a bacterium, an alga and a crustacean. In a screening phase the most sensitive test, Microtox, can be used. The use of an ecotoxicological approach can have added value to hazard and risk assessment of discharges to the receiving waters and can contribute to the environmental management of the treatment plant.

Effects of diamond nanoparticle exposure on the internal structure and reproduction of Daphnia magna

Nanomaterials have significant technological advantages but their release into the environment also carry potential ecotoxicological risks. Carbon-based nanoparticles and particularly diamond nanoparticles have numerous industrial and medical applications. The aim of the present study was to evaluate the toxic effects of diamond nanoparticles with an average particle size of 20 nm on the survival, reproduction and tissue structure of the freshwater crustacean Daphnia magna. The chronic toxicity test results showed 100% mortality at concentrations higher than 12.5 mg l(-1) and that reproduction inhibition occurred in concentrations higher than 1.3 mg l(-1). Light microscopy showed that diamond nanoparticles adhere to the exoskeleton surface and accumulate within the gastrointestinal tract, suggesting that food absorption by the gut cells may be blocked. The results support the use of chronic approaches in environmental protection as part of an integrated environmental monitoring and assessment strategy.

Ecotoxicological assessment of industrial wastewaters in Trancão River Basin (Portugal)

It is important to assess the toxicity of complex effluents, since chemical evaluation alone is insufficient to protect the environment. Direct Toxicity Assessment is valuable in the decision process regarding the final disposal of complex wastewaters as it measures the total effects of the discharge, because of its known and unknown chemicals, additionally having some degree of ecological relevance. In Portugal, ecotoxicity tests are not used on a regular basis to control wastewaters. So, an integrated ecotoxicological, physical, and chemical study of wastewaters from 17 industries, in the Trancão River Basin, was carried out viewing proposing a test battery to be used in wastewater evaluation. An approach which does not include an ecotoxicological characterization may not properly evaluate the potential risks of effluent discharges, especially when they are complex. From the study carried out the use of a battery of assays to apply in the monitoring of complex wastewaters was proposed, including Microtox test, Daphnia test, and an algal test. Moreover, the added value of the ecotoxicological assessment of industrial wastewaters was demonstrated and could support the implementation of EU Directives (e.g. IPPC, WFD) within the Portuguese situation.

Ecotoxicological evaluation of wastewater in a municipal WWTP in Lisbon area (Portugal)

Abstract Wastewater management has a central role in sustainable development, and, in this context, an integrated management of wastewater treatment plants (WWTP) can be important. WWTP discharge complex effluents and for a new strategy in environmental protection ecotoxicological evaluation should complement the usual chemical evaluation. The EU project WW4Environment was set up for a WWTP located in Lisbon area and discharging into Tagus estuary (Portugal). One of the main objectives of the project is to optimize the management of the WWTP in terms of environmental impact. A battery of toxicity tests with organisms bearing different functions at the ecosystem level (the bacterium Vibrio fischeri, the alga Pseudokirchneriella subcapitata, the crustaceans Thamnocephalus platyurus and Daphnia magna, and the plant Lemna minor) was used to characterize the wastewater in the different treatment phases. V. fischeri, test organism for Microtox test, was the most sensitive species in WWTP samples evaluation. Mic...

A multi-integrated approach on toxicity effects of engineered TiO2 nanoparticles

The new properties of engineered nanoparticles drive the need for new knowledge on the safety, fate, behavior and biologic effects of these particles on organisms and ecosystems. Titanium dioxide nanoparticles have been used extensively for a wide range of applications, e.g, self-cleaning surface coatings, solar cells, water treatment agents, topical sunscreens. Within this scenario increased environmental exposure can be expected but data on the ecotoxicological evaluation of nanoparticles are still scarce. The main purpose of this work was the evaluation of effects of TiO2 nanoparticles in several organisms, covering different trophic levels, using a battery of aquatic assays. Using fish as a vertebrate model organism tissue histological and ultrastructural observations and the stress enzyme activity were also studied. TiO2 nanoparticles (Aeroxide® P25), two phase composition of anatase (65%) and rutile (35%) with an average particle size value of 27.6±11 nm were used. Results on the EC50 for the tested aquatic organisms showed toxicity for the bacteria, the algae and the crustacean, being the algae the most sensitive tested organism. The aquatic plant Lemna minor showed no effect on growth. The fish Carassius auratus showed no effect on a 21 day survival test, though at a biochemical level the cytosolic Glutathione-S-Transferase total activity, in intestines, showed a general significant decrease (p<0.05) after 14 days of exposure for all tested concentrations. The presence of TiO2 nanoparticles aggregates were observed in the intestine lumen but their internalization by intestine cells could not be confirmed.