Giuseppe Nano

Combined slurry and solid-phase bioremediation of diesel contaminated soils.

This work investigates, at a laboratory and pilot-scale, the influence of various operating parameters on the combined slurry and solid-phase bioremediation technique for a diesel contaminated soil. For slurry-phase bioreactors (SPB), it has been found that, as far as famine conditions are attained at the end of the react cycle, a low hydraulic retention time and a low slurry recycle ratio allows for a better utilization of the reactor volume. A 7-day slurry-phase bioreactor treatment has been shown to provide enough contaminant removal allowing the soil drawn from the slurry-phase bioreactors to be fed effectively to the solid-phase bioreactors (SoPB) for completing the soil cleanup. However, an important improvement of the solid-phase bioreactor performance has been found using soil additives, namely sand and surfactants. While the first soil additive improves pile porosity and consequently oxygen diffusion, the latter increases contaminant bioavailability.

Lactic acid production by electrodialysis Part I: Experimental tests

Lactic acid, the production of which from cheap raw materials is attractive due to its great potential in the production of biodegradable polymers, can be obtained from fermentation broths using electrodialysis. This work discusses the feasibility of this process using commercial membranes, together with the influence of several operating parameters on the electrodialysis stack performance. It was found that it is possible to operate with high current efficiency values, while the overall recovery of sodium lactate depends on the current density. Electroosmotic water transport limits the maximum concentration value achievable using this technique.

Removal of water pollutants by Lemna gibba

Abstract Duckweed can be used in water treatment systems to remove various pollutants such as ammonia and phosphate. In this work the influence of temperature and concentration of pollutants on the rates of removal of ammonia, phosphate, and organic load was investigated experimentally. From the results of such experiments, a few mathematical relations were deduced, which allow prediction of the rate of pollutant removal. These relations represent the first step in constructing a mathematical model able to simulate duckweed-based aquatic systems.

Lactic acid production by electrodialysis Part II: Modelling

One interesting alternative to the usual end-of-pipe processes for treating waste water produced during cheese-making involves its fermentation to sodium lactate. Then, electrodialysis can be used to recover free lactic acid from the fermentation broth. The design and optimization of such a process is aided by a suitable mathematical model. This work presents a model of the performance of an electrodialysis stack to be used in such a process. Its reliability has been assessed by comparison with experimental data for free lactic acid recovery from sodium lactate solutions. A suitable procedure for estimating some process-dependent parameters is also discussed.

Analysis of the sodium lactate concentration process by electrodialysis

Abstract Electrodialysis is an interesting technique developed for recovering and purifying salts and acids from fermentation broths. In this work the concentration process of sodium lactate solutions was analyzed using a two-compartment electrodialytic unit equipped with commercial membranes (Neosepta AMX and CMX, Tokuyama Soda). The influence of several operating parameters on the overall process performance was investigated. For instance, it came out that at low current density values such membranes are able to operate a perfect separation of opposite charges, resulting in a good process performance. Moreover, water transport by electro-osmosis has to be considered, hence lowering the stack performance. Lastly, the reliability of a general mathematical model for this process was tested. The consistency between experiments and model results is fairly good, allowing the use of this model for design and optimization purposes.

Emission of air pollutants from burning candles with different composition in indoor environments

Candle composition is expected to influence the air pollutants emissions, possibly leading to important differences in the emissions of volatile organic compounds and polycyclic aromatic hydrocarbons. In this regard, the purity of the raw materials and additives used can play a key role. Consequently, in this work emission factors for some polycyclic aromatic hydrocarbons, aromatic species, short-chain aldehydes and particulate matter have been determined for container candles constituted by different paraffin waxes burning in a test chamber. It has been found that wax quality strongly influences the air pollutant emissions. These results could be used, at least at a first glance, to foresee the expected pollutant concentration in a given indoor environment with respect to health safety standards, while the test chamber used for performing the reported results could be useful to estimate the emission factors of any other candle in an easy-to-build standardised environment.

Improving biotreatment efficiency of hot waste air streams: experimental upgrade of a full plant

Biological methods as bio and biotrickling filtration are an energy-efficient and economical alternative to treat biodegradable odorants and volatile organic compounds (VOCs) in order to obey stringent releases regulations that have arisen during the last few decades. In this work a plant upgrade case study, employing these techniques, is presented. It refers to a critical situation in which off air streams, characterized by medium odorous compounds loads and high temperatures, were treated using a biofilter only. In that context, sufficient removal efficiencies were not achieved. Therefore, it has been proposed to replace the existing biofilter by a biotrickling one implementing a minimal number of structural plant modifications.

Design Guidelines for Push-Pull Ventilation Systems Through Computational Fluid Dynamics Modeling

Open surface tanks often are used in industrial practice. When harmful substances are involved, control of worker exposure requires the use of a local ventilation system. The push-pull system, among others, involves a jet of air that is blown from one side of the tank and collected by an exhaust hood on the opposite side; this system can save up to 50% of the ventilation air. Several guidelines are available for design of such a ventilation system, mainly based on experimental results. However, their validity is confined inside a narrow operating window. In this work a mathematical model developed based on computational fluid dynamics has been used to extend the validity of the existing guidelines outside the range in which they have been validated, with particular reference to tank width and to the velocity of the air drafts.

Dynamic modelling of waste-water treatment plants based on Lemna gibba

Abstract In this paper, a comprehensive process model able to simulate the behaviour of a waste-water treatment plant based on Lemna gibba has been developed. This model accounts for the main chemical and biochemical phenomena involved in a natural waste-water treatment system. Several comparisons with experimental data obtained both in mini-ponds and in realsize plants have confirmed the reliability of the model predictions.

Classification and optimization of potentially runaway processes using topology tools

Abstract Fast and strongly exothermic reactions can exhibit a well-known phenomenon called “thermal runaway”. To identify high productivity and safe conditions for these reactions, with particular reference to industrial semibatch processes carried out using both isothermal and isoperibolic temperature control mode, a dedicated classification/optimization software has been implemented. This software is able to both classify a set of operating parameters from the thermal stability viewpoint and identify the optimum reacting/synthesis conditions using a topological criterion that binds the so-called “QFS region”, where reactants accumulation is low and all the heat released is readily removed by the cooling equipment. During the search for system optimum a number of safety and quality constraints can be taken into account. The software reliability, in terms of both classification and optimization ability, has been tested using both laboratory and industrial scale experimental data. Obtained results confirm a good agreement between theoretical predictions and experimental evidence.