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Abstract The contamination of water bodies by heavy metals is one of the main concerns for environmental protection, due to the intrinsic toxicity and long lifetime of these compounds. Consequently, there is a pressing need to reduce emissions of heavy metals in wastewater, using efficient and cost-effective remediation techniques, which at the same time will not produce toxic residues, e.g. adsorption on activated carbon. The present work deals with the optimal design and operation of adsorption columns for the removal of cadmium and nickel from synthetic aqueous solutions, both in single-compound and binary systems. Thermodynamic experimental tests were carried out on activated carbon samples (GAC), produced starting from a commercial carbon by chemical oxidation with either nitric acid or hydrogen peroxide, to support the dynamic study and to identify the sample with higher adsorption capacity. Subsequently, the dynamic behavior of Cd and Ni adsorption was studied by means of software simulations in order to attain an optimized column design. Several working configurations were explored, investigating the effects of GAC physical and chemical properties, pollutant concentration and flow rate, for a wide application in process operations. Moreover, the intertwining between thermodynamic and dynamic parameters in the performance of a fixed-bed was highlighted. All the transport phenomena that can affect the overall performance, i.e. axial dispersion, external film diffusion and intraparticle mass transport were considered. In particular, for the internal transport, both pore and surface diffusions were taken into account and considered to occur in parallel; moreover the contribution of pollutant surface diffusivity, which is usually neglected in the commonly adopted model because difficult to estimate, was isolated and its influence on the overall adsorption rate was elucidated. The general formulation of the kinetic model allowed estimating the contribution of each adsorption rate controlling parameter and the effect exerted by the main fluid dynamic parameters, hence representing a fundamental tool for the design and optimization of an adsorption column.

The adverse effects of agriculture and livestock production on the environment are well-known and require mitigation in order to achieve sustainability in the food production chain. This study focused on adverse effects related to biogeochemical flows of phosphorus and nitrogen cycles which natural balances have been greatly disturbed by current practices. To assess the potential benefits and detrimental effects of proposed mitigation measures, adequate impact indicators are required. The challenge lies in identifying and providing indicators that cover the important aspects of environmental sustainability and allow a direct comparison of policy alternatives. A review of potential indicators that are also consistent with those used to indicate the performance of agricultural and general sustainability (i.e. the European Green Deal) led to the selection of fifteen agri-environmental indicators covering the main environmental issues in agriculture. The indicators identified offered an effective representation of environmental behaviour and would be useful in communicating a comprehensive ‘dashboard’ for professional end users of solutions to nutrient recovery and nutrient efficiency improvement in arable and livestock systems. The selected dashboard indicators (DBI) covered the dimensions of ‘use of primary resources’, ‘emissions to the environment’ and ‘resilience to climate change’. Five case studies were investigated to test the DBI using an Excel questionnaire applying the qualitative approach of the Delphi method together with expert knowledge. As expected, the results indicated that there were potential benefits of the technologies in terms of improved ‘nutrient recovery’ and decreased ‘nitrate leaching’. Potential disadvantages included increased electricity and oil consumption and greater ammonia volatilisation due to the increased use of organic fertilisers. The indicator ‘water’ received more neutral responses; thus, the specific technology was not expected to consistently affect the indicator. In relation to ‘particulate matter’, the results were indicated to be ‘unknown’ for some solutions due to the difficulty of predicting this indicator. Furthermore, methodologies for estimating quantitative values for the dashboard indicators were proposed, and a quantitative assessment was performed for the solution ‘catch crops to recover nutrients’, confirming the responses in the qualitative assessment. The dashboard indicators selected covered the main aspects of the solutions, identified in more comprehensive studies of environmental impacts, as being suitable for the rapid assessment of technologies for nutrient recovery in agriculture. As such, they can be used as a pre-screening method for technologies designed to improve the environmental sustainability of arable and livestock systems. info:eu-repo/semantics/publishedVersion

Water scarcity is a major problem faced in different parts of the world due to various reasons. Highly humid places closer to sea offers discomfort to the people and the moisture transport inside the building causes hazards to the interior and exterior over a period of time. However, both the water scarcity and high humidity problem can be addressed with the development of a novel system. Present work focuses on the dehumidification process where highly humid air moves over the copper coils wound helically, with cold water running through it. Vapor compression refrigeration cycle main�tains the temperature of the cold water. The dehumidification is enhanced with the condensation of moisture and then dehumidified air enters the room. The fresh water collected is used as drinking water. Thermal para �meters like temperature and humidity are measured and the overall dehu� midification efficiency is assessed. Water condensation rate is found to be optimum for the air velocity 2 m/s with a dehumidification coil temperature of 2°C. These values are 22% and 31% higher than the water temperatures of 5°C and 10°C. The average water harvesting from the current system is 1.90 kg/hr. or 2.57 liters per hour (l/hr.).