Massimiliano Fabbricino

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.

An environmental friendly cycle for Cr(III) removal and recovery from tannery wastewater.

Results of a lab-scale experimental study are presented that aim to verify the use of ground shrimp shells, not otherwise conditioned, as an adsorbent material to remove chromium(III) from tannery wastewater. The obtained removal efficiency is found to be always over 90%, confirming the capacity of the tested materials to remove chromium(III). The adsorption process is well described by the Brauner-Emmett-Teller isotherm, indicating the existence of both weak and strong adsorption sites inside the shells. Kinetic tests allow to verify that the removal process takes place rapidly during the first 2 h and then tends to reach a plateau: the pseudo second-order model is found to be able to simulate with good approximation, the adsorption process. Analyses comparing the treatment process using shrimp shells vs. other chemical products frequently used for chromium removal, supported by microscopic observations, indicate that the efficiency obtained using shrimp shell is comparable to the efficiency obtained using sodium bicarbonate and sodium hydroxide, but the removal mechanism is different as the adsorption on the polysaccharidic matrix of the shells prevails over the precipitation of chromium salts. The skin tanned with recovered chromium is found to be of low quality; on the contrary satisfying tanning results are obtained using, as tanning agent, the sludge produced by the adsorption process without any further treatment, except for pH correction.

An integrated programme for municipal solid waste management

A mathematical model is used in planning an integrated programme for the management of municipal solid waste to solve an economical optimisation problem and allow preliminary decisions to be made at the operational planning phase. The model, based on networks depicting the municipal solid waste management cycle, is simple to apply and furnishes easily assimilated results that facilitate management choices. Its application in an optimised area within the Regione Campania in Italy demonstrates how it may be used to evaluate the economic advantages pertaining to different municipal solid waste collection and treatment options.

Effect of soil/contamination characteristics and process operational conditions on aminopolycarboxylates enhanced soil washing for heavy metals removal: a review

The present paper analyzes literature data dealing with the use of aminopolycarboxylates for chemical washing of heavy metals contaminated soils. The aim is to rationalize and organize the up-to-date knowledge of process dependence on different parameters, in order to give a contribution to the development of washing protocols applicable for process optimization. Process efficiency is found to be dependent on i) parameters related to soil composition, ii) parameters related to contaminant characteristics and iii) operating parameters. The effect that each of them, according to the reviewed experimental studies, has on process efficiency, is highlighted, and the interdependence among them is presented as a key point to understand the overall removal mechanism and therefore to calibrate its application case-by-case.

Effect of moisture on disintegration kinetics during anaerobic digestion of complex organic substrates

The role of the moisture content and particle size (PS) on the disintegration of complex organic matter during the wet anaerobic digestion (AD) process was investigated. A range of total solids (TS) from 5% to 11.3% and PS from 0.25 to 15 mm was evaluated using carrot waste as model complex organic matter. The experimental results showed that the methane production rate decreased with higher TS and PS. A modified version of the AD model no.1 for complex organic substrates was used to model the experimental data. The simulations showed a decrease of the disintegration rate constants with increasing TS and PS. The results of the biomethanation tests were used to calibrate and validate the applied model. In particular, the values of the disintegration constant for various TS and PS were determined. The simulations showed good agreement between the numerical and observed data.

Modified Anaerobic Digestion Model No.1 for dry and semi-dry anaerobic digestion of solid organic waste.

The role of total solids (TS) content in anaerobic digestion of selected complex organic matter, e.g. rice straw and food waste, was investigated. A range of TS from wet (4.5%) to dry (23%) was evaluated. A modified version of the Anaerobic Digestion Model No.1 for a complex organic substrate is proposed to take into account the effect of the TS content on anaerobic digestion. A linear function that correlates the kinetic constants of three specific processes (i.e. disintegration, acetate and propionate up-take) was included in the model. Results of biomethanation and volatile fatty acids production tests were used to calibrate the proposed model. Model simulations showed a good agreement between numerical and observed data.

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.

Photofermentative production of hydrogen and poly-β-hydroxybutyrate from dark fermentation products

The aim of this work is to investigate the hydrogen and poly-β-hydroxybutyrate (PHB) production during the photofermentative treatment of the effluent from a dark fermentation reactor fed with the organic fraction of municipal solid waste. Two different inocula, an adapted culture of Rhodobacter sphaeroides AV1b and a mixed consortium of purple non sulphur bacteria have been investigated under the same operational conditions. Different hydrogen productivities of 364 and 559NmL H2 L-1 were observed for the Rhodobacter sphaeroides and the mixed culture consortium tests, respectively: the consortium of PNSB resulted 1.5-fold more productive than the pure culture. On the other hand, Rhodobacter sphaeroides culture showed a higher PHB productivity (155mg PHB g COD-1) than the mixed culture (55mg PHB g COD-1). In all the tests, the concomitant H2 and PHB production was associated to a dissolved COD removal higher than 80%.

Analysis of Heavy Metal Sources for Urban Creeks in the Czech Republic

The study analyzes the presence and the origin of heavy metals in environmental compartments affected by anthropogenic activities. The paper presents the results of a field study performed on the sediments of two of the main small urban creeks of the city of Prague (Czech Republic). The aim of the survey was to verify the presence and bioavailability of heavy metals (Cu, Cr, Ni, Pb, Zn) in the aquatic environment (water as well as bottom sediments), and to assess the source of these pollutants. The results were processed to evaluate the enrichment factor and the partition coefficient, and were statistically analyzed through the analysis of variance and the principal component analysis. Comparison with relevant environmental quality standards showed that measured heavy metal concentrations were always lower than the probable effect concentration (PEC). On the contrary, the threshold effect concentration (TEC) was frequently exceeded. Sequential extraction analysis showed that the bioavailability of studied metals is quite high, suggesting that they could be easily released from the sediment to the aquatic environment. Overall, several sources of pollution, different for the different metals, were identified, all related with anthropogenic factors.

Changes of the corrosion potential of iron in stagnation and flow conditions and their relationship with metal release

This study examined the behavior of corrosion potential (Ecorr) of iron exposed to drinking water during episodes of stagnation and flow. These measurements showed that during stagnation episodes, Ecorr values decrease prominently and consistently. This decrease is initially rapid but it becomes slower as the stagnation time increases. During flow episodes, the Ecorr values increase and reach a quasi-steady state. Experiments with varying concentrations of dissolved oxygen showed that the decrease of Ecorr values characteristic for stagnation is likely to be associated with the consumption of dissolved oxygen by the exposed metal. The corrosion potential of iron and its changes during stagnation were sensitive to the concentrations of sulfate and chloride ions. Measurements of iron release showed that both the absolute values of Ecorr measured prior to or after stagnation episodes were well correlated with the logarithms of concentrations of total iron. The slope of this dependence showed that the observed correlations between Ecorr values and Fe concentrations corresponded to the coupling between the oxidant consumption and changes of Fe redox status. These results demonstrate that in situ Ecorr measurements can be a sensitive method with which to ascertain effects of hydrodynamic conditions and short-term variations of water chemistry on metal release and corrosion in drinking water. This approach is valuable practically because Ecorr measurements are precise, can be carried out in situ with any desired time resolution, do not affect the state of exposed surface in any extent and can be carried out with readily available equipment.