G. Libralato

Polymer functionalized nanocomposites for metals removal from water and wastewater: An overview.

Pollution by metal and metalloid ions is one of the most widespread environmental concerns. They are non-biodegradable, and, generally, present high water solubility facilitating their environmental mobilisation interacting with abiotic and biotic components such as adsorption onto natural colloids or even accumulation by living organisms, thus, threatening human health and ecosystems. Therefore, there is a high demand for effective removal treatments of heavy metals, making the application of adsorption materials such as polymer-functionalized nanocomposites (PFNCs), increasingly attractive. PFNCs retain the inherent remarkable surface properties of nanoparticles, while the polymeric support materials provide high stability and processability. These nanoparticle-matrix materials are of great interest for metals and metalloids removal thanks to the functional groups of the polymeric matrixes that provide specific bindings to target pollutants. This review discusses PFNCs synthesis, characterization and performance in adsorption processes as well as the potential environmental risks and perspectives.

Ecotoxicity of engineered TiO2 nanoparticles to saltwater organisms: An overview

The innovative properties of nanomaterials make them suitable for various applications in many fields. In particular, TiO2 nanoparticles (nTiO2) are widely used in paints, in cosmetics and in sunscreens that are products accessible to the mass market. Despite the great increase in the use of such nanomaterials, there is a paucity of general information about their potential effects to the aquatic species, especially to saltwater ones. Moreover, the difficulties of determining the effective exposure scenario make the acquired information low comparable. In this work, questions about the complexity of the real exposure scenario determination are discussed. The state of the art, concerning the experimental activities with nTiO2 toward the saltwater organisms is firstly illustrated, providing statistical information about the different matrices, organisms and nanoparticles employed. A comparison of the nTiO2 ecotoxicity effects, grouped by taxonomic classes, is provided illustrating their relative experimental conditions. Findings show the need to develop specific protocols for toxicity tests with ENPs to control the variability of experimental conditions. Some advices are finally proposed for the future experimental activities.

Phytotoxicity of ionic, micro- and nano-sized iron in three plant species

Potential environmental impacts of engineered nanoparticles (ENPs) can be understood taking into consideration phytotoxicity. We reported on the effects of ionic (FeCl3), micro- and nano-sized zerovalent iron (nZVI) about the development of three macrophytes: Lepidium sativum, Sinapis alba and Sorghum saccharatum. Four toxicity indicators (seed germination, seedling elongation, germination index and biomass) were assessed following exposure to each iron concentration interval: 1.29-1570mg/L (FeCl3), 1.71-10.78mg/L (micro-sized iron) and 4.81-33,560mg/L (nano-iron). Exposure effects were also observed by optical and transmission electron microscopy. Results showed that no significant phytotoxicity effects could be detected for both micro- and nano-sized zerovalent irons, including field nanoremediation concentrations. Biostimulation effects such as an increased seedling length and biomass production were detected at the highest exposure concentrations. Ionic iron showed slight toxicity effects only at 1570mg/L and, therefore, no median effect concentrations were determined. By microscopy, ENPs were not found in palisade cells or xylem. Apparently, aggregates of nZVI were found inside S. alba and S. saccharatum, although false positives during sample preparation cannot be excluded. Macroscopically, black spots and coatings were detected on roots of all species especially at the most concentrated treatments.

Ecotoxicological evaluation of Mediterranean dredged sediment ports based on elutriates with oyster embryotoxicity tests after composting process

The ecotoxicological effect of dredged sediments was estimated by embryo-larval toxicity of the oyster Crassosstrea gigas in sediment elutriates (filtered and unfiltered). The study covers the main ports from the French Mediterranean coast. Composted sediments from a navy harbour (A), a commercial port (B) and two composite specimens (C and D) obtained after mixing various sediments were taken into consideration. Effective concentrations affecting 50% of larvae (EC50) were obtained from different elutriate concentrations (from 0 to 100%). Toxicity results obtained from filtered elutriates decreased according to the following gradient: sample A (5.68%), B (20.50%), C (37.60%) and D (47.17%). Chemical concentrations in whole sediments were in agreement with those in elutriates. Among the measured contaminants in elutriates, Cu and Zn resulted as the main contributors to toxicity. Dissolved organic carbon played an important role by exerting a protective effect against the toxicity of dissolved Cu. Toxicity results were interpreted on the basis of toxicity scores to give indication about sediment quality which provided more severe judgement than risk score based on chemical concentrations in sediments.

Seawater ecotoxicity of monoethanolamine, diethanolamine and triethanolamine.

Monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) are compounds with potential acute, sub-chronic and chronic toxicity effects towards aquatic species. A literature review highlighted the existence of a gap in the knowledge on their toxicity with saltwater testing species. A battery of toxicity tests including the alga Phaeodactylum tricornutum Bohlin, the bivalve molluscs Crassostrea gigas (Thunberg) and Mytilus galloprovincialis (Lmk), and the crustacean Artemia franciscana, was considered to update and improve the existing ecotoxicological information. Data were provided as the Effective Concentration that induces a 50% effect in the observed population (EC50), Lowest Observed Effect Concentration (LOEC) and No Observed Effect Concentration (NOEC). EC50, LOEC and NOEC values were compared with a reviewed database containing the existing ecotoxicological data from saltwater organisms.

Influence of the salinity adjustment methods, salts and brine, on the toxicity of wastewater samples to mussel embryos

One of the main problems of the Whole Effluent Toxicity is related to the use of bioindicator species representative of the target environment. Most wastewater discharges are of fresh water, so their salinity has to be adjusted when they are discharged to transitional and marine coastal waters, in order to perform toxicity bioassays with reliable organisms. At the moment, there is no optimum technique to allow sample salinity to be adjusted and no specific information regarding salinity adjustment when bivalves are being considered for toxicity test performance. This paper provides information on the potential use of different methods to adjust the salinity of hotel/domestic wastewater samples with different brands of natural and synthetic Dry Salts (DS) and HyperSaline Brine (HSB) for use in the embryo larval development bioassay with the mussel Mytilus galloprovincialis. HyperSaline Brine derived from reconstructed artificial seawater proved to be more viable for wastewater salinity adjustment than DS.

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.

Influence of storage methods, refrigeration or freezing, on the toxicity of wastewater samples to oyster embryos

One of the main concerns in wastewater whole effluent assessment is the sampling phase and the sample chain of custody before any toxicity evaluation. The major problem is related to establishing the correct method for sample storage in order to perform toxicity bioassays. The toxicity of some domestic and glass factory industrial wastewater samples stored both by refrigeration at 4 ± 1 °C for no more than three days, and freezing at −18 ± 1 °C for no more than one month was compared via the embryo larval development bioassay with the oyster Crassostrea gigas. The results showed no significant differences between the toxicities of refrigerated and frozen wastewater samples. The wastewater classification, according to a score based on four toxicity classes, showed that the preservation methods did not alter the toxicity classification of the samples. In particular, it was demonstrated that the samples considered as ‘not acutely toxic’ after refrigeration were also found to have this classification after freezing.

Nanotechnologies for Environmental Remediation

The exploration on nanomaterials and their fascinating and enhanced properties has implicated the focusing on their applications embracing a wide range of processes on nanometer scale. In this perspective, nanotechnology in water treatment applications is offering and presenting now new approaches to overcome the limitations of the traditional treatment technologies. This chapter describes several types of nanomaterials that could be used in wastewater treatment underlining their advantages with respect the traditional systems.

Performance assessment of AS-SBR and UF-MBR for hotel wastewater treatment

A large number of tourist structures in Venice (Italy) have small sized on-site treatment systems for their wastewater. Due to its historical characteristics, the city has no public sewerage system and untreated hotel wastewater represents a serious hazard for its lagoon environment. This study focused on the wastewater facilities installed in two hotels adopting an Activated Sludge Sequencing Batch Reactor (AS-SBR) and an Ultra-Filtration Membrane Biological Reactor (UF-MBR). Their performance was checked in terms of both traditional physico-chemical and ecotoxicological parameters, the importance of which has recently been recognised by EU regulatory dispositions and OSPAR indications. Acute and sub-chronic endpoints were both considered on a whole effluent toxicity basis by means of Vibrio fischeri and Crassostrea gigas, respectively. The two months monitoring survey evidenced that the UF-MBR was more efficient than the AS-SBR in providing high-quality discharges under both chemical and ecotoxicological viewpoints.