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Abstract Economically harvesting energy from a microbial fuel cell (MFC), increasing its electrical power production, and developing its role as a practical energy supply, needs a low-cost and high-performance design of the MFC compartments. According to this strategy, a novel monolithic membrane electrode assembly (MEA) was fabricated and evaluated as an air–cathode in a single-chamber MFC (SCMFC). The MEA was made of bacterial cellulose (BC), conductive multi-walled carbon nanotubes (CNT), and nano-zycosil (NZ). BC, as a nano-celluloses with oxygen barrier property, can maintain anaerobic conditions for the anode compartment. Binder-less CNT coating on BC avoids costly binders such as poly-tetra fluoro ethylene (PTFE) and Nafion and decreases the MEA charge transfer resistance. NZ, as a very cheap modifier, not only prevents the anolyte leakage but also provides more MEA’s active sites for the oxygen reduction reaction (ORR). The electrochemical performance of the MEA was compared to a PTFE- based gas diffusion electrode (GDE) in the SCMFC. The MEA cell provided a pulse power density of 1790 mW/m2, roughly twice as high as the pulse power density of GDE (920 mW/m2). SCMFC’s internal resistance decreased from 1.84 KΩ (with GDE) to 0.8 KΩ (with MEA). Also, the cell’s columbic efficiency increased from 4.2% (with GDE) to11.7% (with MEA). Additionally, the capacitance of the MEA (65 mF) was much higher than the value for GDE (0.73 mF). Thus, the MEA compared to the GDE showed higher performance in the SCMFC for electricity generation and wastewater treatment at a lower cost.

Abstract Italy reformed its water and sanitation services in 1994. The strategy aimed at transforming public entities, financed by the central budget, into self-sufficient professional companies regulated at arms' length. Nearly 20 years after, the reform has failed to deliver (despite some partial success). Italians have been divided in two parties: those blaming public sector inefficiencies and calling for competitive tendering; and those refusing to privatize water and willing to go back to the fiscal budget. In this article, we suggest that both parties are wrong. Underperformance is not related to the ownership structure of water companies, but rather to poor regulatory design and lack of understanding of the regulatory requirements that are implicit in the management model chosen, namely the concession contract.

ABSTRACTAn overview is given of an International Atomic Energy Agency Coordinated Research Project (CRP) on the treatment of irradiated graphite (i-graphite) to meet acceptance criteria for waste disposal. Graphite is a unique radioactive waste stream, with some quarter-million metric tons worldwide eventually needing to be disposed of. The CRP has involved 24 organizations from 10 Member States. Innovative and conventional methods for i-graphite characterization, retrieval, treatment and conditioning technologies have been explored in the course of this work, and offer a range of options for competent authorities in individual Member States to deploy according to local requirements and regulatory conditions.

Abstract A novel integrated energy system based on a geothermal heat source and a liquefied natural gas heat sink is proposed in this study for providing heating, cooling, electricity power, and drinking water simultaneously. The arrangement is a cascade incorporating a flash-binary geothermal system, a regenerative organic Rankine cycle, a simple organic Rankine cycle, a vapor compression refrigeration cycle, a regasification unit, and a reverse osmosis desalination system. Energy, exergy, and exergoeconomic methods are employed to analyze the suggested system. A parametric study based on decision variables is carried out to better assess the system performance. Four different multi-objective optimization problems are also carried out. At the most excellent trade-off solution specified by the TOPSIS method, the system attains 29.15% exergy efficiency and 1.512 $/GJ total product cost per exergy unit. The main output products are consequently calculated to be 101.07 kg/s cooling water, 570.44 kW net output power, and 81.57 kg/s potable water.

This work represents the first step to set up a toxicity testing procedure and to evaluate the sensitivity of the test microorganism to several classes of environmental pollutants. First, three different techniques were employed to standardise the microbial inoculum, then two different toxicity assessment protocols have been compared: Microtox and a dehydrogenase (DHase) activity inhibition test. The main goal was the optimisation of a microbial bioassay based on the dehydrogenase activity (DHase) inhibition in Pseudomonas fluorescens bacterial strain ATCC 13525. Triphenyl tetrazolium chloride (TTC) was used as electron acceptor and its reduction produces Triphenyl formazane (TPF). The P. fluorescens DHase inhibition bioassay was investigated for being a reliable and rapid method for assessing toxicity. The optimisation of the operating conditions resulted in a repeatable bioassay. Then, P. fluorescens and Vibrio fischeri sensitivity were firstly compared by testing Zn++, one of the reference compounds for Microtox test. In addition, other compounds (Ni++, Cd++, Cu++, phenol) were also tested with both bioassays. A high statistical significance of data was obtained with the logistic curve. The present work has demonstrated that P. fluorescens is as sensitive as Microtox culture (V. fischeri), for some of the metal ions. With reference to organic compounds, the lower sensitivity of P. fluorescens to phenol makes its use difficult in organic polluted samples.

Rapid population growth invokes the need for a vast amount of water conservation. Many centralized water treatment systems will reach their limits and face difficulties to provide clean industrial water to rural areas. The infrastructure for water distribution is dilapidated in many regions and only little of the wastewater is currently being recycled. One solution could be the expansion of decentralized membrane bioreactor (MBR) systems in peri-urban areas. MBR achieves excellent water qualities, whereas the comparatively high energy consumption is the main drawback. Therefore, MBR plants need to be optimized in their specific energy consumption to obtain a high degree of self-sufficiency for decentralized locations. There is a dire need for innovative controlling strategies and efficient coupling with energy supply systems through novel applications. This chapter will highlight the basic approaches to reduce the MBR's overall energy consumption and ways to establish sustainable, autonomous operations without sacrificing the process quality.

The European Union is currently in the process of transformation toward a circular economy model in which different areas of activity should be integrated for more efficient management of raw materials and waste. The wastewater sector has a great potential in this regard and therefore is an important element of the transformation process to the circular economy model. The targets of the circular economy policy framework such as resource recovery are tightly connected with the wastewater treatment processes and sewage sludge management. With this in view, the present study aims to review existing indicators on resource recovery that can enable efficient monitoring of the sustainable and circular solutions implemented in the wastewater sector. Within the reviewed indicators, most of them were focused on technological aspects of resource recovery processes such as nutrient removal efficiency, sewage sludge processing methods and environmental aspects as the pollutant share in the sewage sludge or its ashes. Moreover, other wide-scope indicators such as the wastewater service coverage or the production of bio-based fertilizers and hydrochar within the wastewater sector were analyzed. The results were used for the development of recommendations for improving the resources recovery monitoring framework in the wastewater sector and a proposal of a circularity indicator for a wastewater treatment plant highlighting new challenges for further researches and wastewater professionals.

Abstract Small Mediterranean islands are remote, off-grid communities characterized by carbon intensive electricity systems coupled with high energy consuming desalination technologies to produce potable water. The aim of this study is to propose a novel dynamic, multi-objective optimization approach for improving the sustainability of small islands through the introduction of renewable energy sources. The main contributions of our approach include: (i) dynamic modelling of desalination plant operations, (ii) joint optimization of system design and operations, (iii) multi-objective optimization to explore trade-offs between potentially conflicting objectives. We test our approach on the real case study of the Italian Ustica island by means of a comparative analysis with a traditional non-dynamic, least cost optimization approach. Numerical results show the effectiveness of our approach in identifying optimal system configurations, which outperform the traditional design with respect to different sustainability indicators, limiting the structural interventions, the investment costs and the environmental impacts. In particular, the optimal dynamic solutions able to satisfy the whole water demand allow high levels of penetration of renewable energy sources (up to more than 40%) to be reached, reducing the net present cost by about 2–3 M€ and the CO2 emissions by more than 200 tons/y.

A dynamic model was developed for representing the abatement of sulfates and metals in column reactors inoculated with sulfate reducing bacteria. The model framework includes both bioactive mechanisms (bioreduction of sulfates and bioprecipitation of metals) and passive abiotic mechanism (sorption onto the column filling). Sorption capacities of column filling material were determined by dedicated tests of sulfate and cadmium removal. These experimental data implemented in model framework denoted that before steady state sorption mechanism could predominate over bioactive mechanism. Sensitivity analysis confirmed that, varying sorption and bioreduction parameters in typical range of laboratory scale systems, sorption cannot be neglected before steady state. An operative equation was obtained by literature data and model simulations showing that in the majority of works reported in the literature the operational times used for column experiments are not sufficient to saturate column sorption capacity. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 70–80, 2014