Maria Letizia Ruello

Heavy metal shock load in activated sludge uptake and toxic effects

Abstract Waste sludge from laboratory units at four different steady-state conditions (5–20 days sludge ages) was employed for studying heavy metal shock load by the jar test system. Metal uptake (Hg, Cd, Ni) and oxygen depletion rates were simultaneously followed. The potential adsorption constants ( k am ) measured reveal a metal affinity sequence Hg > Cd > Ni, in partial contrast to the metal toxicity (MT) one, Hg > Ni > Cd. This suggests different sludge adsorption sites. Hg is preferentially adsorbed on the cell, while Cd is adsorbed on extracellular polymer slimes and Ni on capsular polymers and the cellular wall. Therefore sludge age influences Cd and Ni toxicity, while no effect is observed for Hg.

Paper Mill Sludge Ash as Supplementary Cementitious Material

Paper mill sludge is often incinerated for heat recovering and also for an important volume reduction. In Italy about 6x10 5 tons of paper sludge is yearly produced giving 60kg of paper ash per ton. In this project, the ash coming from burning of paper mill sludge from primary mechanical separation process, fired as single fuel, was studied in order to evaluate its use as supplementary cementitious material in concrete manufacturing. On the basis of the data collected it can be concluded that the paper mill sludge ash, if replaced by 5 to 10% of Portland cement, show a positive effect on the mechanical performance of the concrete. On the other hand, due to its high fineness and consequently high water absorption, it requires a higher dosage of water, so that the use of paper ash should not be higher than 10% by weight of cement.

Influence of Binders and Lightweight Aggregates on the Properties of Cementitious Mortars: From Traditional Requirements to Indoor Air Quality Improvement

Innovative and multifunctional mortars for renders and panels were manufactured using white photocatalytic and non-photocatalytic cement as binder. Unconventional aggregates, based on lightweight materials with high specific surface and adsorbent properties, were adopted in order to investigate the possible ability to passively improve indoor air quality. The reference mortar was manufactured with traditional calcareous sand. Results show that even if the mechanical properties of mortars with unconventional aggregates generally decrease, they remain acceptable for application as render. The innovative mortars were able to passively improve indoor air quality in terms of transpirability (70% higher), moisture buffering ability (65% higher) and depolluting capacity (up to 75% higher) compared to traditional ones under the current test conditions.

Appraisal of a hybrid air cleaning process

Nowadays, there is an amplified interest in maintaining suitable indoor air quality (IAQ). Besides a wide range of available interventions, air cleaners are considered a valuable tool, since based on inexpensive and easily implementing technologies to improve IAQ. The purpose of this work is to combine the TiO2-photocatalysis with the electrostatic and adsorption processes, in order to improve efficiency and reliability. A TiO2-photocatalytic oxidation combined with an electrostatic filter has been studied. Nitrogen oxides reduction and degradation of many VOC over different catalyst support were monitored jointly with CO and CO2 production. The coupling of photocatalysis with an external electric field enhances efficiency of the process. The choice of materials with diversified adsorptive characteristics plays an important role in the durability of the process over time.

Solutions for critical raw materials under extreme conditions: A review

In Europe, many technologies with high socio-economic benefits face materials requirements that are often affected by demand-supply disruption. This paper offers an overview of critical raw materials in high value alloys and metal-matrix composites used in critical applications, such as energy, transportation and machinery manufacturing associated with extreme working conditions in terms of temperature, loading, friction, wear and corrosion. The goal is to provide perspectives about the reduction and/or substitution of selected critical raw materials: Co, W, Cr, Nb and Mg.

Soil Zinc contamination from corrosion of galvanized structures

The present work relates to galvanized structures with several years of time life subjected to atmospheric corrosion, like galvanized high tension steel pylons. The mass and fate of zinc released is evaluated both via empirical and experimental procedures. The corrosion rate determination requested atmospheric condition characterization, especially for SO 2 concentration and experimental activities focused on soil sampling around pylons. The soil zinc content, total and exchangeable, is determinates by different analytical procedures. The zinc diffusion in environment and the zinc extension under the top soil is evaluated using 1-dimensional mathematical model for miscible species in porous soil.

Persistence of heavy metals in river sediments

The objective of this study was to assess heavy metals accumulation and equilibrium phenomena in river sediment, in relation to water quality, and to assess metals lability, analysing whether and how easily heavy metals are available to generic biota. The diffuse gradient in thin film technique was used to assess the effective concentration (C E). The solid–liquid distribution coefficient of the metals labile pool (K dl) was calculated to include it in risk analysis within a more realistic frame. The Esino River was chosen for the case study. The results confirmed the need to determine K d experimentally; values of K d taken from the literature resulted in errors of some orders of magnitude. Metals speciation, environmental conditions, the type and texture of the sediment, features of the water, organic fraction, pH and salinity can all influence the outcome. The results showed that the two main parameters on which K d depends are chemical oxygen demand and specific surface area. C E, which takes into account the contribution of both the water and the labile fraction in the sediment, is a key parameter and may be 5–100×the concentration in the pore water.

Design and calibration of an organic diffusive probe to extend the diffusion gradient technique to organic pollutants.

The objective of this study was to develop a method for measuring the mobility of persistent organic pollutants in the solid phase of soils within the context of environmental pollution risk assessment. A new diffusive probe, purposely designed by adapting the diffusive gradient technique method, measures labile organic species by immobilizing them after diffusion through a thin deionized water layer. The measure of the mass accumulated is used to calculate the flow of pollutant from solid phase to pore water. Naphthalene was chosen as a model persistent organic pollutant. The probe was calibrated at different temperatures and was then tested in several microcosms at different porosity and reactivities with naphthalene (one clay soil, two sandy soils and one natural soil). The probe response showed good agreement with the expected different abilities of the solid phases in restoring the solution phase. The concentration of naphthalene in the pore water was well buffered by rapid equilibria with the solid phase in the investigated natural soil. In contrast, pore water concentration in the sandy soils decreased rapidly and the flow was slackened, especially for the sandy soil with finer particles. In clay, only a fraction of the total naphthalene content was present in the labile fraction, while the remaining was tightly bound and was not released to the pore water. Therefore, this first stage of testing points out that the diffusive gradient technique, if optimized, can properly quantify the mobility of organic pollutants in soil.

Bacteria Removal and Viability Attenuation by Means of an Electrostatic Barrier

This study is focused on bacterial control through the removal and attenuation of viability by means of a commercial electrostatic air cleaner inserted in the ductwork of a central heating and air-conditioning system. Adapting the system to include an electrostatic barrier resulted, on an average, in removal of 88% of the bacteria in the airflow. In addition, the ratio of viable to non-viable organisms, calculated on the basis of epifluorescence measurements, was changed appreciably by passage through the electrostatic filter. Evaluation of performance was followed by two different strategies of sampling-analysis: a plate count method and epifluorescence microscopy. The system overall was highly efficient in removing the bacteria, since those few that evaded the filter underwent attenuation of around 50% of their viability on passage through it. This work suggests a strong positive effect when an electrostatic barrier is inserted in a ventilation duct.

Pollutants site ratio as appointment of highway, industrial and farming sources

An in-situ field study was conducted to measure the outdoor pollutant concentrations necessary to design the ventilation-filtration system and improve the indoor air quality of a public building. The area of study is located in the flat terrain of the Italian Po valley, near a traffic-congested highway and surrounded by an industrial factory and many farms. The quality of the ambient air was evaluated monitoring NO2, toluene and xylenes concentrations, and was compared with that in urban atmospheres and related to traffic emissions. Measurements of pollutant were performed with passive diffusion samplers with the aim to test the hypothesis that the highway contribution to ambient air quality varies with the logarithm of the distance. The toluene/xylenes ratio measured at the building site and at the highway source ratio suggested that beside vehicular emission, industrial and farming sources were governing the volatile organic compounds in the area. The present study confirmed that NO2 concentration at a nearby highway varied linearly with the logarithm of the distance from the highway, but the slope found for this regression was somewhat steeper than those reported in the literature for urban conditions. The reason for this has not been related to augmented atmospheric dispersion differences. Instead, the presence of hydroxyl radicals and volatile organic compounds of either agricultural or industrial origin may affect a complex ozone-hydrocarbon reactivity. The results delineate the pollutant site ratio and the traffic equivalent distance as useful parameters for the source emissions characterisation and the selection of an effective control technology.