Exploring the effect on the environment of encapsulated micro- and nano-plastics into asphalt mastics for road pavement.

A new environmental problem is represented by the huge transformation of plastic waste released into the environment into small fragments, the so called micro- and nano-plastics, due to atmospheric phenomena. The smaller the size of the plastic fragments, the more their spreading into environmental compartments. The aim of this study is to test encapsulation into asphalt mastics of waste plastic material (WPM) as sustainable strategy to obtain road flexible pavements and to evaluate the potential release in water of micro and nano plastics. A new mastic mixing method was developed to blend the WPM with the bitumen contained into a bitumen emulsion (BE60/40) by adopting low mixing temperatures. Three different WPM contents, equal to 5, 10 and 20% by the weight of the bitumen contained in the BE60/40, were adopted to produce the mastics; the mastics' rheological properties, obtained by frequency sweep and multiple stress creep and recovery tests, were compared to those of a traditional asphalt mastic containing limestone filler. The aging of asphalt mastics was analyzed by soaking them in water and gradually lowering and raising temperature between -10 and 60 °C at predefined intervals. The addition of WPM improved greatly the asphalt mastic performance; in particular, for a WPM content of 10%, the rheological response in terms of stiffness remained unchanged after the mastic underwent thermal excursions in water. Encapsulation of micro and nano plastics into mastics reduced of more than 99% their potential water release.

Role of organic nanoparticles on transport and fate of various dyes in aqueous solution.

This work studies the interaction of organic nanoparticles (ON) with various dyes in aqueous solution, to elucidate the role of ON on transport and fate of dyes in the environment, and on dyes removal from wastewater. Studied dyes are Acid Red 66 (AR66), Methylene Blue (MB), Reactive Black 5 (RB5), and Reactive Violet 5 (RV5). ON are extracted from organic matter of anthropogenic origin through resuspension of its colloidal fraction, and successive filtration and dialysis of the obtained suspension. Mechanisms of interaction are investigated initially through three-dimensional excitation emission matrix (3DEEM) analysis. Obtained data indicate that dynamic interactions occur strongly between dye molecules and ON aggregates. 3DEEM spectra of mixed samples containing ON together with one of the tested dyes, present a shape similar to the one of ON alone, but each of them is characterized by specific differences in terms of peaks quenching and shift. The analysis of these singularities suggests that dye molecules are bound to the functional groups of ON through H-bonds, according to the following steps: i) dyes reach the surface of ON aggregates; ii) the molecules pass through the hydrophilic surface of ON aggregates, and reach their hydrophobic core; iii) the dyes are sequestrated into the hydrophobic core of ON aggregates. Nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies analysis confirm the formation of supramolecular aggregates with stable micellar hydrophobic structure, mainly consisting of aliphatic fractions of ON, which explain the disappearance of aromatic groups signals from dyes.

Sustainable asphalt mastics made up recycling waste as filler.

The continuous growth of waste is generating worldwide more and more increasing related environmental concerns. Anything that is not recycled or recuperated from waste represents a loss of raw materials and other production factors used in the manufacture, transport and consumer phases of the product. This research explored the potential of three waste namely Construction and Demolition (CD) waste, Fly Ash (FA), and Jet Grouting (JG) waste as fillers in comparison to the traditional limestone one for making hot asphalt mastics for road pavement, through a rheological analysis and environmental compatibility tests towards the release of potentially toxic elements. A total of eight asphalt mastics were prepared by using two filler-to-binder weight ratios (f/b) of 0.5 and 1 for blending each filler with a neat bitumen 50/70 penetration grade. The Frequency Sweep test and the Multiple Stress Creep and Recovery (MSCR) test were carried out to investigate the rheological properties of the asphalt mastics. Asphalt mastics containing FA and JG fillers were found to be more mechanically and environmentally efficient than traditional limestone mastic in particular by adopting an f/b equal to 1 where it was observed higher complex shear modulus values, G*, (on average 50% compared to the traditional asphalt mastic) and lower non-recoverable creep compliance values, Jnr, (on average 35% compared to the traditional asphalt mastic) at all test temperatures investigated. Based on the suggested ranking methodology, CD emerged as the filler performing in the same way of the traditional one. All the waste containing mastics, showed up noticeable environmental compatibility, being the potentially toxic elements completely immobilized into the mastics' structure e practically not releasable into acidic water, highlighting the waste recycling for road pavements as primary strategy to immobilize hazardous wastes.

Supramolecular aggregation of colloidal natural organic matter masks priority pollutants released in water from peat soil.

Natural organic matter (NOM) from Sphagnum peat soil is extracted in water and subjected to several investigations to obtain structural and conformational information. Data show that the extracted NOM is self-organized in colloidal aggregates of variable sizes (from nano to micro scales, depending on the solvent composition, i.e., ultrapure water, solutions with denaturing agents, acetone, ethanol). Aggregates are formed by highly heterogeneous classes of organic compounds. According to the results of nuclear magnetic resonance and fluorescence measurements, the three-dimensional structure of aggregates, revealed by scanning electron microscope imaging, is supposed to be stabilized by the exposition of polar functional groups to the solvent, with consequent formation of hydrogen bonds, dipole-interactions and cation bridging. In contrast, the inner part of the aggregates displays hydrophobic features and is hypothesized to be further reinforced by the establishment of π-stacking interactions. The structure is assumed to be a supramolecular aggregation of small-medium oligomeric fragments (Max 750 Da) in which priority pollutants are entrapped by dispersive forces. The structures are shown to be nanosized spheroidal particles further aggregated to form higher dimension supra-structures. Carbohydrates play primary role, stabilizing the structure and giving marked hydrophilic properties to the aggregates.

Dark fermentation of complex waste biomass for biohydrogen production by pretreated thermophilic anaerobic digestate.

The Biohydrogen Potential (BHP) of six different types of waste biomass typical for the Campania Region (Italy) was investigated. Anaerobic sludge pre-treated with the specific methanogenic inhibitor sodium 2-bromoethanesulfonic acid (BESA) was used as seed inoculum. The BESA pre-treatment yielded the highest BHP in BHP tests carried out with pre-treated anaerobic sludge using potato and pumpkin waste as the substrates, in comparison with aeration or heat shock pre-treatment. The BHP tests carried out with different complex waste biomass showed average BHP values in a decreasing order from potato and pumpkin wastes (171.1 ± 7.3 ml H2/g VS) to buffalo manure (135.6 ± 4.1 ml H2/g VS), dried blood (slaughter house waste, 87.6 ± 4.1 ml H2/g VS), fennel waste (58.1 ± 29.8 ml H2/g VS), olive pomace (54.9 ± 5.4 ml H2/g VS) and olive mill wastewater (46.0 ± 15.6 ml H2/g VS). The digestate was analyzed for major soluble metabolites to elucidate the different biochemical pathways in the BHP tests. These showed the H2 was produced via mixed type fermentation pathways.

Optimization of the treatment cycle of pressed-off leachate produced in a facility processing the organic fraction of municipal solid waste.

The paper investigates, at a laboratory scale, the applicability of anaerobic digestion for the treatment of pressed-off leachate produced in a biomechanical treatment plant for municipal solid waste. Batch tests show that the anaerobic process proceeds smoothly and produces about 10,000 mL of methane per litre of treated leachate. The process is characterized by a lag phase lasting about 30 days, and is completed in about 2 months. Chemical oxygen demand (COD) and volatile fatty acids monitoring allows studying process kinetics that are modelled through a triple linear expression. Physical and biological treatments are also investigated to reduce the residual organic charge of the produced digestate. The best performances are obtained via aerobic degradation followed by assisted sedimentation. This cycle reduces the residual COD of about 85%, and allows the correct disposal of the final waste stream.

Thermal pretreatment of olive mill wastewater for efficient methane production: control of aromatic substances degradation by monitoring cyclohexane carboxylic acid.

Anaerobic digestion is investigated as a sustainable depurative strategy of olive oil mill wastewater (OOMW). The effect of thermal pretreatment on the anaerobic biodegradation of aromatic compounds present in (OMWW) was investigated. The anaerobic degradation of phenolic compounds, well known to be the main concern related to this kind of effluents, was monitored in batch anaerobic tests at a laboratory scale on samples pretreated at mild (80±1 °C), intermediate (90±1 °C) and high temperature (120±1 °C). The obtained results showed an increase of 34% in specific methane production (SMP) for OMWW treated at the lowest temperature and a decrease of 18% for treatment at the highest temperature. These results were related to the different decomposition pathways of the lignocellulosic compounds obtained in the tested conditions. The decomposition pathway was determined by measuring the concentrations of volatile organic acids, phenols, and chemical oxygen demand (COD) versus time. Cyclohexane carboxylic acid (CHCA) production was identified in all the tests with a maximum concentration of around 200 µmol L(-1) in accordance with the phenols degradation, suggesting that anaerobic digestion of aromatic compounds follows the benzoyl-CoA pathway. Accurate monitoring of this compound was proposed as the key element to control the process evolution. The total phenols (TP) and total COD removals were, with SMP, the highest (TP 62.7%-COD 63.2%) at 80 °C and lowest (TP 44.9%-COD 32.2%) at 120 °C. In all cases, thermal pretreatment was able to enhance the TP removal ability (up to 42% increase).

Effect of total solids content on methane and volatile fatty acid production in anaerobic digestion of food waste.

This work investigates the role of the moisture content on anaerobic digestion of food waste, as representative of rapidly biodegradable substrates, analysing the role of volatile fatty acid production on process kinetics. A range of total solids from 4.5% to 19.2% is considered in order to compare methane yields and kinetics of reactors operated under wet to dry conditions. The experimental results show a reduction of the specific final methane yield of 4.3% and 40.8% in semi-dry and dry conditions compared with wet conditions. A decreasing trend of the specific initial methane production rate is observed when increasing the total solids concentration. Because of lack of water, volatile fatty acids accumulation occurs during the first step of the process at semi-dry and dry conditions, which is considered to be responsible for the reduction of process kinetic rates. The total volatile fatty acids concentration and speciation are proposed as indicators of process development at different total solids content.

Assessment of environmental parameters effect on potentially toxic elements mobility in foreshore sediments to support marine-coastal contamination prediction.

Potentially toxic elements (PTEs) presence in marine sediments can significantly affect the environmental quality and negatively influence economy and recreational activities in related areas. Accordingly, contamination monitoring and control in the marine environment is a fundamental task. In this work, four PTEs behavior (i.e. As, Hg, Pb, and Zn) in sandy foreshore sediments (SFSs) was thoroughly investigated at different pH, redox potential and temperature conditions of the marine water. For all the tests, the released As was 2.7-6 times higher than its initial concentration in water. Nonetheless, final mass balances showed that preferential release in the liquid phase occurred for Pb and Hg (up to 10 % and 9.1 %, respectively). Moreover, final Zn and Hg content increase in SFSs labile fractions indicated their higher bioavailability after the tests. The obtained results outline an approach useful to predict the contaminants behavior in marine matrices and support environmental monitoring and preservation strategies.

Characterization of anthropogenic organic matter and its interaction with direct yellow 27 in wastewater: Experimental results and perspectives of resource recovery.

The concept of natural organic matter of anthropogenic origin is introduced and its characteristics and interaction with chemical pollutants are investigated by adopting several distinct analytic methodologies. Scanning electron microscopy indicates that the used sample of anthropogenic organic matter (AOM) has an amphiphilic nature, which allows its supramolecular organization in water. Fourier transform infrared spectroscopy, in turn, gives a clear indication about the presence of polysaccharide markers, lipidic and amidic fractions, and suggests the absence of free organic acid. AOM sample and AOM mixed with dye sample were examined by the three-dimensional excitation-emission matrix fluorescence spectra and the nuclear magnetic resonance mono-dimensional spectra. The results highlighted the interactions occurring between the AOM and the reactive dye, selected as a representative chemical pollutant. Electron Spin Resonance confirms that the used AOM is able to completely include the dye in its structure. Overall, the obtained results indicate that the fate, transport, and toxicity of pollutants in the environment can be drastically influenced by the presence of AOM.

Bioaugmentation strategy to enhance polycyclic aromatic hydrocarbons anaerobic biodegradation in contaminated soils.

This paper proposes an innovative bioaugmentation approach for the remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soils, based on a novel habitat-based strategy. This approach was tested using two inocula (i-24 and i-96) previously enriched through an anaerobic digestion process on wheat straw. It relies on the application of allochthonous microorganisms characterized by specific functional roles obtained by mimicking a natural hydrolytic environment such as the rumen. The inocula efficiency was tested in presence of naphthalene alone, benzo[a]pyrene alone, and a mix of both of them. In single-contamination tests, i-24 inoculum showed the highest biodegradation rates (84.7% for naphthalene and 51.7% for benzo[a]pyrene). These values were almost 1.2 times higher than those obtained for both contaminants with i-96 inoculum and in the control test in presence of naphthalene alone, while they were 3 times higher compared to the control test in presence of benzo[a]pyrene alone. In mixed-contamination tests, i-96 inoculum showed final biodegradation efficiencies for naphthalene and benzo[a]pyrene between 1.1 and 1.5 higher than i-24 inoculum or autochthonous biomass. Total microbial abundances increased in the bioaugmented tests in line with the PAH degradation. The microbial community structure showed the highest diversity at the end of the experiment in almost all cases. Values of the Firmicutes active fraction up to 7 times lower were observed in the i-24 bioaugmented tests compared to i-96 and control tests. This study highlights a successful bioaugmentation strategy with biological components that can be reused in multiple processes supporting an integrated and environmentally sustainable bioremediation system.

Data of OECD soil and leachate resulting from irrigation with aqueous solution containing trace metals at increasing sodium concentration.

The accumulation of trace metals in soils is one of the main drawbacks when reclaimed waters are used as irrigation sources in agriculture. Such secondary water sources often also contain high levels of salinity and in detail sodium. How the presence of sodium influences the fate of trace metals in the environment is still obscure and of primary importance in defining sustainable agricultural management guidelines. Standard OECD soil columns were subjected to 25 days irrigation with aqueous solutions containing trace concentrations of Cd, Cu, Ni and Zn at increasing sodium content. The dataset is supplementary to the data presented and discussed in "Effect of sodium concentration on mobilization and fate of trace metals in standard OECD soil" [1]. The leachates collected from the columns were deeply characterized in terms of concentration of metals, organic (monitored through UV-VIS, 3DEEM, E4/E6 ratio, COD) and inorganic matter (monitored as Al concentration). The dataset was analyzed by PCA and "Paerson" correlation coefficient.

Effect of sodium concentration on mobilization and fate of trace metals in standard OECD soil.

The effect of different Na concentrations on the fate of trace metals (Cd, Cu, Ni, Zn) in standard OECD soil was evaluated by performing soil leaching column experiments. Five Na concentrations added in synthetic irrigation water (0, 1, 5, 10, 50 mM) were studied in order to evaluate the fate of the metals contained in both the irrigation water leachate and the soil layer. In all experiments, metals mostly accumulated on the top soil layer (0-0.5 cm), at variable concentrations according to the Na content in the artificial irrigation water. Nevertheless, concentration peaks of metal contamination occurred at different sampling time in the soil leachates depending on the metal and on influent water sodicity. Peaks of metals in the leachate appeared simultaneously with the release of organic matter and/or release of Al, suggesting significant involvement of colloids in metals transport. Sodium concentration (10-50 mM) was demonstrated to highly reduce colloidal mobilization leading to the accumulation of more than 95% of the influent metal in the top soil layer. Conversely, low Na concentrations (1-5 mM) favored colloidal transport leading to the recovery of metals in the soil leachates.

Modified Sample Preparation Approach for the Determination of the Phenolic and Humic-Like Substances in Natural Organic Materials By the Folin Ciocalteu Method.

A novel modification of the sample preparation procedure for the Folin-Ciocalteu colorimetric assay for the determination of total phenolic compounds in natural solid and semisolid organic materials (e.g., foods, organic solid waste, soils, plant tissues, agricultural residues, manure) is proposed. In this method, the sample is prepared by adding sodium sulfate as a solid diluting agent before homogenization. The method allows for the determination of total phenols (TP) in samples with high solids contents, and it provides good accuracy and reproducibility. Additionally, this method permits analyses of significant amounts of sample, which reduces problems related to heterogeneity. We applied this method to phenols-rich lignocellulosic and humic-like solids and semisolid samples, including rice straw (RS), peat-rich soil (PS), and food waste (FW). The TP concentrations measured with the solid dilution (SD) preparation were substantially higher (increases of 41.4%, 15.5%, and 59.4% in RS, PS and FW, respectively) than those obtained with the traditional method (solids suspended in water). These results showed that the traditional method underestimates the phenolic contents in the studied solids.

Assessment of trace heavy metals dynamics during the interaction of aqueous solutions with the artificial OECD soil: Evaluation of the effect of soil organic matter content and colloidal mobilization.

A micro-contamination phenomenon was reproduced and studied at lab-scale, mimicking the irrigation of a standard artificial soil with a water solution containing three Heavy Metals (HMs) at trace concentration level. To assess the dynamics of micro-pollutants accumulation and migration trough the soil, the organic matter in the soil was varied, together with sodicity of the irrigation water. Accumulation of the investigated contaminants was observed mainly in the top layer (≤1 cm) of the irrigated soil. This was attributed to the high interaction capacity of the soil compared to the low HM concentrations in the water phase. HMs transport pattern was described assuming a multi-component mechanism including: i) the interaction of HMs with the colloidal phase of the soil; ii) the slow and constant release of small molecular weight ligands detaching from the soil immobile matrix; iii) the transportation of HMs through the soil by these low molecular weight chaperon molecules. The mobility was directly related to the soil organic matter (SOM), since higher amount of SOM correspond to a higher number of chaperon molecules. In the first centimetre of the soil the metals were mostly bound to the acid labile fraction. Very low mobilization was observed with increasing sodicity in the leaching water, since such conditions were unfavourable to the colloidal mobilization of SOM. This indicated that water/soil transfer of pollutant is not only related to the contaminant concentration in the irrigation water but also to the characteristics of the aqueous solution and to the physical-chemical properties of the soil.

Methane and VFA production in anaerobic digestion of rice straw under dry, semi-dry and wet conditions during start-up phase.

This work investigates the start-up phase of anaerobic digestion in wet, semi-dry and dry conditions of rice straw analysing the role of volatile fatty acid (VFA) production on process kinetics. Methane production yields and biodegradation kinetics in reactors operated under wet semi-dry and dry conditions were investigated. The experimental results showed a reduction in the specific final methane production yield of 57% and 63% in, respectively, semi-dry (TS = 14.8%) and dry (TS = 23.4%) conditions compared to wet (TS = 4.8%) conditions. The total VFA concentration and speciation are proposed as indicators of process development at different total solids content. High VFA concentrations were found in dry conditions, with a maximum total VFA concentration of 2110 mg/kg in dry conditions, 930 mg/kg in semi-dry conditions and 180 mg/kg in wet conditions.

Use of chitosan and chitosan-derivatives to remove arsenic from aqueous solutions--a mini review.

Arsenic removal has become a relevant concern due to the final confirmation of its behaviour as chronic human carcinogen, corresponding to an ever-increasing contamination of water, soil and crops in many parts of the world. Developing easily accessible removal strategies is therefore a primary environmental matter. Chitosan and chitosan derivatives show good adsorption performances against arsenic removal and are considered low cost products, easily obtainable. This review provides a summary of recent advances of the application of these compounds in the area of sorption sciences for arsenate and arsenite removal from water, focusing on equilibrium and kinetic mechanisms.