Alessandra Cesaro

Sonolysis and ozonation as pretreatment for anaerobic digestion of solid organic waste

This study aims to compare the efficiency of sonolysis and ozonation in improving anaerobic biodegradability of source sorted organic fraction of municipal solid waste, for the enhancing of biogas production and energy recovery as well. The methane yield of solid organic material anaerobic digestion is significantly affected by substrate availability, which can be favoured by pretreatments. In this investigation, both sonolysis and ozonation effects on substrate solubilisation and anaerobic biodegradability were evaluated under different treatment conditions. Results show that both pretreatments can significantly improve the solubilisation of organic solid waste. However, during ozonation experiments, no correlation was observed between increased solubilisation and biogas production: the application of higher ozone doses led to the formation of by-products less biodegradable than untreated substrate. This evidence makes the ultrasound process more efficient than ozonation and addresses further studies for sonolysis optimisation as pretreatment for solid waste anaerobic digestion.

Enhanced biogas production from anaerobic codigestion of solid waste by sonolysis

This paper examines the effectiveness of sonolysis in improving the anaerobic biodegradability of the organic fraction of municipal solid waste coming from mechanical selection, thus enhancing biogas production and energy recovery as well. Methane yield of solid organic material anaerobic digestion is significantly affected by substrate availability that was evaluated, in this investigation, through organic matter solubilisation tests carried out at different conditions of ultrasound treatment. Results show that sonolysis can significantly improve the solubilisation of organic solid waste, thus allowing higher biogas production from anaerobic treatment of sonicated substrates. After 45 days, the biogas produced during anaerobic codigestion tests for the sonicated mixture was 24% higher than untreated one. Therefore, these results can lay the basis for the development of technologies useful to produce high biogas quantities, in order to improve clean energy generation from biowaste.

Removal of Endocrine Disruptors from Urban Wastewater by Advanced Oxidation Processes (AOPs): A Review

Over the last years the growing presence of endocrine disrupting compounds in the environment has been regarded as a serious sanitary issue. The more and more frequent detection of these compounds in the effluents of wastewater treatment plants poses the risk associated to their persistence into the aquatic systems as well as to their adverse effects on both public health and environment. As conventional systems do not allow their efficient removal, great attention has been raised towards their possible treatment by Advanced Oxidation Processes (AOPs). They rely on the action of hydroxyl radicals, which are highly reactive species, able to oxidize recalcitrant and non-biodegradable pollutants. AOPs can either provide contaminant partial degradation or their complete removal. As their effectiveness has been proved for a wide spectrum of both organic and inorganic pollutants, they are considered a suitable option for the treatment of contaminated aqueous media, especially when combined with conventional biological processes. This paper aims at reviewing main AOPs for the removal of endocrine disruptors, in order to highlight the most important features of different technologies, thus providing their comparative assessment. To this end, a brief overview of the most frequently detected endocrine disruptor compounds was also discussed, in order to clarify their fate into the environment as well as the contamination pathways of greatest concern for human health.

Enhanced ozonation of selected pharmaceutical compounds by sonolysis.

In search of new options to achieve removal of pharmaceuticals in the environment, combined ultrasound and ozonation has become a focus of intense investigation for wastewater treatment. In this study, three pharmaceuticals were selected as model compounds for degradation experiments: diclofenac (DCF), sulfamethoxazole (SMX) and carbamazepine (CBZ). Comparison of the degradation rates for both ozonation and combined ultrasound/ozonation treatments was performed on single synthetic solutions as well as on a mixture of the selected pharmaceuticals, under different experimental conditions. For single synthetic solutions, the efficiency removal for ozonation reached 73%, 51% and 59% after 40 min for DCF, SMX and CBZ, respectively. Comparable results were obtained for pharmaceuticals in mixture. However, the combined ultrasound/ozone treatment was found to increase degradation efficiencies for both DCF and SMX single solutions up to 94% and 61%, respectively, whereas lower removal yields, up to 56%, was noted for CBZ. Likewise, when the combined treatment was applied to the mixture, relatively low removal efficiencies was found for CBZ (44%) and 90% degradation yield was achieved for DCF.

Alternative stabilisation options of mechanically sorted organic fraction from municipal solid waste prior to landfill disposal

In order to foresee the measures of the Directive 1999/31/EC, waste management policies are focused on the reduction of organic matter landfill disposal, through the recovering of the organic waste stream or the pre-treatment of residual wastes before landfilling. This paper discusses the advantages and disadvantages of possible stabilisation treatments of the mechanically sorted organic fraction of municipal solid waste, to identify the most suitable management action, with regard to landfilling impacts. Experimental results demonstrate that chemical treatment of organic residue provides only temporary stabilisation, while anaerobic digestion treatment represent an interesting option thanks to its energetic and environmental benefits.

Comparative technology assessment of anaerobic digestion of organic fraction of MSW

Anaerobic digestion is the biological degradation process of organic matter under anoxic conditions, with production of methane and inorganic by-products, including carbon dioxide. Over the past years, many studies on anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) have been carried out at laboratory, bench and pilot scale. This work aims to summarize the main features of the OFMSW anaerobic digestion techniques and to define the state of art of this process in Europe, at both research and industrial level. To this end, main experimental results, design solutions and technologies are compared, also in relation to capital and operating costs and data about full scale experiences are reported. Among the different aspects discussed, particular interest has been provided to pretreatment possibilities in relation to substrate biodegradability and biogas production rate. The data collected and examined in this paper stress the aspects to be improved, in order to define future perspectives of the anaerobic process application for OFMSW treatment.

Biotechnological strategies for the recovery of valuable and critical raw materials from waste electrical and electronic equipment (WEEE) – A review

Critical raw materials (CRMs) are essential in the development of novel high-tech applications. They are essential in sustainable materials and green technologies, including renewable energy, emissionfree electric vehicles and energy-efficient lighting. However, the sustainable supply of CRMs is a major concern. Recycling end-of-life devices is an integral element of the CRMs supply policy of many countries. Waste electrical and electronic equipment (WEEE) is an important secondary source of CRMs. Currently, pyrometallurgical processes are used to recycle metals from WEEE. These processes are deemed imperfect, energy-intensive and non-selective towards CRMs. Biotechnologies are a promising alternative to the current industrial best available technologies (BAT). In this review, we present the current frontiers in CRMs recovery from WEEE using biotechnology, the biochemical fundamentals of these bio-based technologies and discuss recent research and development (R&D) activities. These technologies encompass biologically induced leaching (bioleaching) from various matrices,biomass-induced sorption (biosorption), and bioelectrochemical systems (BES).

A device-specific prioritization strategy based on the potential for harm to human health in informal WEEE recycling

In developing countries, the recovery of valuable materials from Waste Electrical and Electronic Equipment (WEEE) is carried out via uncontrolled practices, posing potentially severe risks both to human health and the environment. The assessment of the risk, which depends on both the kind and hazardous properties of the substances contained in WEEE, is currently limited as the exposure scenario for the single informal practice cannot be fully characterized for this purpose. In this context, this work proposes and evaluates a strategy to identify the relative potential harm of different kinds of WEEE by their content in metals, selected as the target substances of concern. This was based on the individual metal content, primarily located in the printed circuit boards (PCBs) of the different devices. The metal composition of the individual PCBs was identified and the dominant unregulated metal recovery practices were reviewed to identify the most suitable parameter to express the toxicity of these metals. Based on a mass-normalized cumulative toxicity, via the inhalation route, individual components were assessed from compositional variation found in the literature. The results is a semiquantitative ranking of individual components, revealing significant differences in potential harm posed by different electronic appliances and an opportunity to provide prioritization strategies in future management.

A comparative technology assessment of the anaerobic digestion of an organic fraction of municipal solid waste

Anaerobic digestion is the biological degradation process of organic matter under anoxic conditions, with production of methane and inorganic by-products, including carbon dioxide. Over the past years, many studies on anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) have been carried out at a laboratory, bench and pilot scale. This work aims to summarize the main features of the OFMSW anaerobic digestion techniques and to define the state-of-the-art of this process in Europe, at both a research and industrial level. To this end, the main experimental results, design solutions and technologies are compared, also in relation to capital and operating costs and data about full scale experiences are reported. Among the different aspects discussed, particular interest has been manifested in pretreatment possibilities in relation to substrate biodegradability and biogas production rate. The data collected and examined in this paper stress the aspects to be improved, in order to define future perspectives of the anaerobic process application for OFMSW treatment.