Ranking sewage sludge management strategies by means of Decision Support Systems: A case study

3nononenoneBertanza, Giorgio; Baroni, Pietro; Canato, MatteoBertanza, Giorgio; Baroni, Pietro; Canato, Matte

Effectiveness in chlorite removal by two activated carbons under different working conditions: a laboratory study

Activated carbon is used in many drinking water facilities because it can remove a broad spectrum of contaminants (e.g., herbicides, pesticides, heavy metals, etc.) or to replace anthracite coal in dual media filters. In recent years, liquid chlorine has been substituted by chlorine dioxide (ClO2) because, for instance, it can remove natural organic matter in raw water without formation of harmful disinfection by-products. Interest in chlorine dioxide is due to formation of chlorite (ClO 2 ), which can be potentially toxic for humans. In this study, the authors investigated the applicability of two activated carbons coming from different matrices (coconuts and bituminous) as technology for chlorite removal. The activated carbons were tested at different conditions (virgin and pre-loaded with some substances) in order to simulate full-scale working situations, and their Freundlich isotherms were determined. The results show a good affinity of virgin carbons in chlorite removal (about 80%), but the pre-loading significantly affected the efficiency of the chlorite removal process, reducing it to only 19%. An investigation into the main removal mechanism used by the carbons for chlorite removal was also done. Results show that activated carbons used both reduction and adsorption processes

Methodology for technical and economic assessment of advanced routes for sludge processing and disposal

In order to meet the environmental legislative framework in force in Europe and reduce sludge processing and disposal costs, several sludge treatment technologies and management strategies have been proposed in the last two decades. The evaluation of their technical and economic suitability, case by case, may be a challenge, since many aspects are involved, so that a robust decision support system should be used. Within the ROUTES project (founded within the EU Seventh Framework Programme), the authors have developed an assessment procedure which allows rating several technical factors (such as system reliability, complexity, safety aspects, modularity, etc.) and estimating capital and operating costs, in case a plant is being upgraded. The comparison between the original (reference) plant and the modified configuration informs about technical hot spots (which are expressed by a traffic light-type colour code) and cost gaps resulting from the implementation of the new solution

Monitoring of a pilot GFO filter for removal of low-concentration arsenic in water

Many water treatment plants (WTPs) were designed to remove ammonia, iron, and manganese simultaneously using biofilters. In some cases (especially in the Pianura Padana area, in Italy) such plants were designed without a specific treatment stage for arsenic removal because its concentration in the groundwater (i.e. 10 to 20 µg/L) was lower than the previous maximum contaminant level (MCL) of 50 µg-As/L; therefore, specific treatments for arsenic removal must be introduced or upgraded in WTPs. In this work, the results of a 19-month monitoring campaign are reported for a pilot granular ferric oxide (GFO) filter installed in an Italian WTP as a polishing stage. The aim was to investigate the performance of GFO with low arsenic concentrations. The results show that, if the groundwater arsenic concentration is close to the MCL, GFO treatment can be cost effective (approximately 80,000 bed volumes have been treated). It was confirmed that GFO can be effective for the removal of both As(III) and As(V) species

Wet Oxidation of Fine Soil Contaminated with Petroleum Hydrocarbons: A Way towards a Remediation Cycle

The aim of this experimental study was to assess the feasibility of using a wet oxidation (WO) process for treating fine soil with a high level of total petroleum hydrocarbons (TPHs). Two samples of soil were spiked with two different contaminants (motor oil, and motor oil + diesel). The samples were subjected to a WO bench plant test, where the effect of the main process parameters (i.e., temperature and reaction time) on the removal of TPHs was investigated. Results show that the WO process is effective for the decontamination of hydrocarbons, and a strong reduction (>85%) can be obtained with the typical working conditions of a full-scale plant (temperature = 250 C, reaction time = 30 min). The solid residue resulting from the WO process was characterized in order to evaluate the recovery options. In terms of chemical characterization, the contents of the pollutants comply with the Italian regulations for commercial and industrial site use. Moreover, the results of the leaching test suggested that these residues could be reused for ceramic and brick manufacturing processes

GaN-on-silicon transistors with reduced current collapse and improved blocking voltage by means of local substrate removal

International audienceWe report on the demonstration of low trapping effects above 1200 V of GaN-on-silicon transistors using a local substrate removal (LSR) followed by a thick backside ultra-wide-bandgap AlN deposition. Substrate ramp measurements show reduced hysteresis up to 3000 V. It has been found that the LSR approach not only enable to extend the operation voltage capabilities of GaN-on-Silicon HEMTs with low on-resistance but also allow to reduce trapping effects directly affecting their dynamic behavior. This work points out that a large part of the electron trapping under high bias occurs at the AlN nucleation layer and Si substrate interface