A New Approach for Bioremediation of Olive Mill Wastewaters: Combination of Straw Filtration and Nanofiltration.

A combination of straw filtration and nanofiltration was investigated for the first time as a sustainable approach aimed at valorizing olive mill wastewaters (OMWs) within a circular economy strategy. Ground straw filters with different granulometry (120, 250 and 500 µm) were tested in the first step to clarify the raw wastewater. The 500 µm filter offered the best performance due to a lower exposed surface of the filtering fibers and a shorter filtering time, allowing us to reduce about 70% of the chemical oxygen demand (COD) of the raw wastewater. Three different commercial membranes in a flat-sheet configuration with a molecular weight cut-off (MWCO) in the range 150-500 Da were tested to fractionate the clarified wastewater according to a dead-end configuration. Among the investigated membranes, a polymeric membrane of 500 Da (NFA-12A) exhibited the highest productivity in selected operating conditions (steady-state values of 11.4 L/m2 h at 20 bar and 24 ± 2 °C). In addition, flux decays for this membrane were lower than the other two tested membranes, indicating a lower propensity to fouling phenomena. Higher rejections towards total polyphenols and total antioxidant activity (TAA) (76.6% and 73.2%, respectively) were also observed for this membrane. Flavanols and hydroxycinnamic acids were retained by more than 99%. The combination of straw filtration and NF with the NFA-12A membrane allowed us to reduce the COD of raw OMWs up to 97.6%. The retentate fraction of this membrane exhibited a TAA of 18.9 ± 0.7 mM Trolox, supporting its propensity for the development of innovative formulations of interest in food and nutraceutical applications.

A model for the adsorption process of water dissolved elements flowing into reactive porous media: Characterization and sizing of water mining/filtering systems.

This study presents a mathematical model describing the adsorption-desorption process of water dissolved elements onto reactive porous materials during filtering operations performed under dynamic flow conditions. The developed model is based on a reversible second order adsorption kinetic featuring the progressive reduction of the purifying capacity of the filtering material due to the gradual exhaustion of the active sites available for solute retention. It enables the simulation of the performances of water filtering systems through the use of parameters having a clear chemical-physical significance or it can be used for the estimation of these parameters to characterize the adsorption properties of the reactive material. Starting from the same adsorptive conceptual model used for the filtering system marked by ongoing flowing conditions, an adaptation for static systems was performed on the mathematical framework in order to process the same chemical physical parameters in both schemes. Adsorption laboratory tests were carried out to validate the developed model. Results show that the kinetic constants and adsorption capacities (a maximum of about 45 mg g-1 was obtained for the tested material) are highly comparable, both within the same experimental system, and between different experimental setup. This confirms the validity of the developed model which is able to perfectly fit the observed concentration data in all tested configurations.

Microplastics in aquatic systems, a comprehensive review: origination, accumulation, impact, and removal technologies.

Although the discovery of plastic in the last century has brought enormous benefits to daily activities, it must be said that its use produces countless environmental problems that are difficult to solve. The indiscriminate use and the increase in industrial production of cleaning, cosmetic, packaging, fertilizer, automotive, construction and pharmaceutical products have introduced tons of plastics and microplastics into the environment. The latter are of greatest concern due to their size and their omnipresence in the various environmental sectors. Today, they represent a contaminant of increasing ecotoxicological interest especially in aquatic environments due to their high stability and diffusion. In this regard, this critical review aims to describe the different sources of microplastics, emphasizing their effects in aquatic ecosystems and the danger to the health of living beings, while examining, at the same time, those few modelling studies conducted to estimate the future impact of plastic towards the marine ecosystem. Furthermore, this review summarizes the latest scientific advances related to removal techniques, evaluating their advantages and disadvantages. The final purpose is to highlight the great environmental problem that we are going to face in the coming decades, and the need to develop appropriate strategies to invert the current scenario as well as better performing removal techniques to minimize the environmental impacts of microplastics.

Groundwater pollution assessment in landfill areas: Is it only about the leachate?

Groundwater is the environmental compartment very often involved in the broader issues related to contaminated sites characterization and reclamation. It is not uncommon to find areas in which some substances directly linked to the petrographic composition of the aquifer reach high values exceeding the limits set by the regulations. These concentrations are defined as Natural Background Levels (NBL) and the need to quantify their real contribution, in areas subject to strong anthropogenic pressures, represents an emerging problem. Global statistical analyses and laboratory testing are proposed here to distinguish between the impacts of different forcing influencing water quality in hydrogeological systems. The study focus on the application of a methodology based on the Component Separation analysis for the NBL estimation of selected chemical species in potentially contaminated aquifers flowing in the proximity of landfill areas, and on the subsequent validation of the results through experimental studies of field samples. A site located in Calabria, Italy, and constituting a typical example of an aquifer which has been subjected to possible contact with the leachate produced by waste degradation is considered. The work is keyed to NBLs characterization of aluminum, iron and manganese and to the identification of their natural component for a proper environmental assessment of the site. Estimated NBLs are consistent with the geochemical composition of site samples. The adopted methodology can represent a useful instrument to distinguish effective anthropogenic contamination from natural conditions and to define realistic environmental clean-up goals.

Photocatalytic inactivation of Escherichia coli bacteria in water using low pressure plasma deposited TiO2 cellulose fabric.

Fabrics obtained from cellulose spinning, extracted from Spanish broom, were coated with TiO2 film, through the low pressure plasma sputtering technique, in order to get antibacterial activity. The obtained fabrics were used for the photocatalytic degradation of Escherichia coli, by irradiation with UV-light emitting diodes (UV-LED), in a batch photocatalytic reactor. Before and after functionalization treatments, cellulosic substrates were chemically characterized by X-ray photoelectron spectroscopy (XPS) analyses. Water Contact Angle (WCA) measurements allowed obtaining information about the hydrophilicity of the materials, while their antibacterial efficiency was determined at several initial concentrations (from 103 up to 108 CFU mL-1) of bacteria in distilled water, bottled water and synthetic wastewater. It was found that photocatalytic reactions were capable of achieving up to 100% bacterial inactivation in 1 h of treatment, following a pseudo-first order kinetic model. No bacterial regrowth was observed after photocatalytic treatments in almost all experimental conditions. In contrast, during photolytic treatment (i.e. in the absence of the TiO2 coated fabrics) bacteria recovered their initial concentration after 3 h in the dark. Finally, the reusability of the plasma modified fibers to inactivate bacteria was studied.

Removal of Endocrine Disrupting Chemicals from Water: Adsorption of Bisphenol-A by Biobased Hydrophobic Functionalized Cellulose.

The aim of this study is to examine the efficiency of biobased Spanish broom (SB) surface modified cellulose fibers to remove bisphenol A (BPA), a well-known endocrine disruptor, from water. Spanish brooms are flowering plants, which are native and abundant to Mediterranean regions. The functionalized fibers (FF) were found to have the best adsorption efficiency at pH 5, due to the optimal hydrophobic interaction between the FF fiber and BPA. Adsorption kinetics of BPA was found to fit well a pseudo-second order reaction. Equilibrium isotherm data were fitted by Langmuir and Freundlich models. A very fast and simple regeneration method was developed and it was observed that adsorption capacity of the fibers was kept almost unchanged after 3 consecutive uses. Bottled water and synthetic wastewater were also tested to assess the efficiency of the process under more realistic water and wastewater treatment conditions. It was found that BPA removal was slightly decreased from 77% in ultrapure water to 64% in synthetic wastewater matrix, indicating that FF has a high selectivity toward BPA, even in the presence of other organic compounds. Overall, it was observed that SB-modified fibers can be a new promising green biotechnology for water purification.

Remediation of hydrocarbons polluted water by hydrophobic functionalized cellulose.

Remediation of water bodies from petroleum hydrocarbons is of the utmost importance due to health risks related to the high toxicity, mutagenicity and carcinogenicity of the hydrocarbons components that may enter into the food chain. Though several methods were proposed to face up this challenge, they are generally not easily feasible at a contaminated site and quite costly. Here we propose a green, cost-effective technology based on hydrophobized Spanish Broom (SB) cellulose fiber. The natural cellulose fiber was extracted by alkaline digestion of the raw vegetable. The hydrophilic cellulose surface was transformed into a hydrophobic one by the reaction with 4,4'-diphenylmethane diisocyanate (MDI) forming a very stable urethane linkage with the hydroxyl groups of cellulose emerging from the fibers surface. Chemical functionalization was performed with a novel solvent-free technology based on a home-made still reactor were the fiber was kept under vortex stirring and the MDI reactant then spread onto the fiber surface by nebulizing it in form of micrometer-sized droplets. The functionalized fiber, characterized by means of WCA measurements, XPS and ATR-FTIR spectroscopy, shows fast adsorption kinetics adsorption capacity as high as 220 mg/g, among the highest ever reported so far in the literature for cellulosic materials.

Study of the adsorption of mercury (II) on lignocellulosic materials under static and dynamic conditions.

WHO has declared mercury as one of the most dangerous pollutants for human health. Unfortunately, several cases of rivers and aquifers contaminated by mercury inevitably poses the problem on how to remediate them. Considerable efforts are being addressed to develop cost-effective methodologies, among which the use of low-cost adsorbing materials. In this paper, the adsorption performances of an alternative lignocellulosic material derived from the Spanish broom plant, are presented. This plant is widely diffused in the world and its usage for Hg(II) removal from water in real working conditions requires only minimal pretreatment steps. A thoroughly investigation on the kinetics and thermodynamics of Hg(II) adsorption on Spanish broom is presented, by using Hg(II) polluted aqueous solutions specifically prepared in order to simulate typical groundwater conditions. Several batch experiments, under static conditions, were carried out in order to evaluate the effect of pH, contact time, adsorbent dosage, initial concentration, temperature. A maximum adsorption capacity of 20 mg L-1 can be obtained at pH 5, following a pseudo second order kinetics. Moreover, adsorption experiments in dynamic conditions were carried out using Spanish broom filters. Interestingly, a systematic, unconventional double S-shape breakthrough curve was observed under different experimental conditions, revealing the occurrence of two adsorption processes with different time scales. This behavior has been fitted by a bimodal Thomas model which, unlike the single Thomas fitting, gives satisfactory results with the introduction of a new parameter related to the fraction of surface active sites involved in the adsorption processes.

Hydraulic Tomography: Continuity and Discontinuity of High-K and Low-K Zones.

Hydraulic tomography is an emerging field and modeling method that provides a continuous hydraulic conductivity (K) distribution for an investigated region. Characterization approaches that rely on interpolation between one-dimensional (1D) profiles have limited ability to accurately identify high-K channels, juxtapositions of lenses with high K contrast, and breaches in layers or channels between such profiles. However, locating these features is especially important for groundwater flow and transport modeling, and for design and operation of in situ remediation in complex hydrogeologic environments. We use transient hydraulic tomography to estimate 3D K in a volume of 15-m diameter by 20-m saturated thickness in a highly heterogeneous unconfined alluvial (clay to sand-and-gravel) aquifer with a K range of approximately seven orders of magnitude at an active industrial site in Assemini, Sardinia, Italy. A modified Levenberg-Marquardt algorithm was used for geostatistical inversion to deal with the nonlinear nature of the highly heterogeneous system. The imaging results are validated with pumping tests not used in the tomographic inversion. These tests were conducted from three of five clusters of continuous multichannel tubing (CMTs) installed for observation in the tomographic testing. Locations of high-K continuity and discontinuity, juxtaposition of very high-K and very low-K lenses, and low-K "plugs" are evident in regions of the investigated volume where they likely would not have been identified with interpolation from 1D profiles at the positions of the pumping well and five CMT clusters. Quality assessment methods identified a suspect high-K feature between the tested volume and a lateral boundary of the model.