• Energy Research
• Closed Access close
• 6. Clean water close
• IT close

A procedure for the design of an aerobic cometabolic process for the on-site degradation of chlorinated solvents in a packed bed reactor was developed using groundwater from an aquifer contaminated by trichloroethylene (TCE) and 1,1,2,2-tetrachloroethane (TeCA). The work led to the selection of butane among five tested growth substrates, and to the development and characterization from the site's indigenous biomass of a suspended-cell consortium capable to degrade TCE (first order constant: 96 L gprotein(-1) day(-1) at 30 °C and 4.3 L gprotein(-1) day(-1) at 15 °C) with a 90 % mineralization of the organic chlorine. The consortium immobilization had strong effects on the butane and TCE degradation rates. The microbial community structure was slightly changed by a temperature shift from 30 to 15 °C, but remarkably affected by biomass adhesion. Given the higher TCE normalized degradation rate (0.59 day(-1) at 15 °C) and attached biomass concentration (0.13 gprotein Lbioreactor(-1) at 15 °C) attained, the porous ceramic carrier Biomax was selected as the best option for the packed bed reactor process. The low TeCA degradation rate exhibited by the developed consortium suggested the inclusion of a chemical pre-treatment based on the TeCA to TCE conversion via β-elimination, a very fast reaction at alkaline pH. To the best of the authors' knowledge, this represents the first attempt to develop a procedure for the development of a packed bed reactor process for the aerobic cometabolism of chlorinated solvents.

Binary and ternary systems of Ni(2+), Zn(2+), and Pb(2+) were investigated at initial metal concentrations of 0.5, 1.0 and 2.0mM as competitive adsorbates using Arthrospira platensis and Chlorella vulgaris as biosorbents. The experimental results were evaluated in terms of equilibrium sorption capacity and metal removal efficiency and fitted to the multi-component Langmuir and Freundlich isotherms. The pseudo second order model of Ho and McKay described well the adsorption kinetics, and the FT-IR spectroscopy confirmed metal binding to both biomasses. Ni(2+) and Zn(2+) interference on Pb(2+) sorption was lower than the contrary, likely due to biosorbent preference to Pb. In general, the higher the total initial metal concentration, the lower the adsorption capacity. The results of this study demonstrated that dry biomass of C. vulgaris behaved as better biosorbent than A. platensis and suggest its use as an effective alternative sorbent for metal removal from wastewater.

Italy is the most important European country in terms of paddy rice production. North Italian districts such as Vercelli, Pavia, Novara, and Milano are known as some of the world's most advanced rice cultivation sites. In 2013 Italian rice cultivation represented about 50% of all European rice production by area, and paddy fields extended for over 216,000 ha. Cultivation of rice involves different agricultural activities which have environmental impacts mainly due to fossil fuels and agrochemical requirements as well as the methane emission associated with the fermentation of organic material in the flooded rice fields. In order to assess the environmental consequences of rice production in the District of Vercelli, the cultivation practices most frequently carried out were inventoried and evaluated. The general approach of this study was not only to gather the inventory data for rice production and quantify their environmental impacts, but also to identify the key environmental factors where special attention must be paid. Life Cycle Assessment methodology was applied in this study from a cradle-to-farm gate perspective. The environmental profile was analyzed in terms of seven different impact categories: climate change, ozone depletion, human toxicity, terrestrial acidification, freshwater eutrophication, marine eutrophication, and fossil depletion. Regarding straw management, two different scenarios (burial into the soil of the straw versus harvesting) were compared. The analysis showed that the environmental impact was mainly due to field emissions, the fuel consumption needed for the mechanization of field operations, and the drying of the paddy rice. The comparison between the two scenarios highlighted that the collection of the straw improves the environmental performance of rice production except that for freshwater eutrophication. To improve the environmental performance of rice production, solutions to save fossil fuel and reduce the emissions from fertilizers (leaching, volatilization) as well as methane emissions should be implemented.

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 Biohydrogen Potential (BHP) of six different types of waste biomass typical for the Campania Region (Italy) was investigated. Anaerobic sludge pre-treated with the specific methanogenic inhibitor sodium 2-bromoethanesulfonic acid (BESA) was used as seed inoculum. The BESA pre-treatment yielded the highest BHP in BHP tests carried out with pre-treated anaerobic sludge using potato and pumpkin waste as the substrates, in comparison with aeration or heat shock pre-treatment. The BHP tests carried out with different complex waste biomass showed average BHP values in a decreasing order from potato and pumpkin wastes (171.1 ± 7.3 ml H2/g VS) to buffalo manure (135.6 ± 4.1 ml H2/g VS), dried blood (slaughter house waste, 87.6 ± 4.1 ml H2/g VS), fennel waste (58.1 ± 29.8 ml H2/g VS), olive pomace (54.9 ± 5.4 ml H2/g VS) and olive mill wastewater (46.0 ± 15.6 ml H2/g VS). The digestate was analyzed for major soluble metabolites to elucidate the different biochemical pathways in the BHP tests. These showed the H2 was produced via mixed type fermentation pathways.

Abstract This study compared the mesophilic and thermophilic anaerobic digestion of chicken manure under two organic loading rates (OLR) i.e. 1.6 and 2.5 kg volatile solids (VS) m−3 d−1. A 180-day continuous study was carried out to analyze the effects of OLR on biogas production, specific methanogenic activities (SMA) and process mass balances. The results demonstrated that the mesophilic reactor yield methane at 252 and 245 mL CH4 g−1 Total Solid at the two OLRs. However, in the thermophilic reactor, the methane yield was lower, i.e.220 mL CH4 g−1 TS for OLR of 1.6 kg VS m−3d−1 and 94 mL CH4 g−1 TS for OLR of 2.5 kg VS m−3d−1. High free ammonia nitrogen (FAN) concentration, particularly at a high OLR, led to a high concentration of VFAs which negatively affected SMA, while under mesophilic condition the VFAs was lower and SMA was not affected. Principal component analysis indicated that OLR, TAN, and FAN have an effect on biogas production. It was concluded that mesophilic and thermophilic reactors could work comparatively well at a low OLR, but that the thermophilic condition had significantly deleterious effects on the efficiency of anaerobic digestion above all at the higher OLR.

A bacterial co-culture, ECO3, constituted by a polychlorobiphenyl degrading bacterium, Pseudomonas sp. strain CPE1, and two chlorobenzoic acid degrading bacteria, could grow on Aroclor 1221 (75 mg/L) as the sole carbon source without accumulating chlorinated aromatic metabolites in the medium; 44.5% of the Aroclor 1221 organic chlorine was detected as chloride ion in the medium after 115 h of incubation in batch condition. When glass beads (diameter = 3 mm, 30% w/v) or Triton X-100 (0.066% v/v) were added to ECO3 cultures, average dechlorination percentages were 80% and 89.5%, respectively, after the same incubation time. These percentages were significantly higher than those previously observed with the only polychlorobiphenyl degrading member of ECO3, CPE1 strain, in the same culture conditions. This result can be ascribed to the capability of the ECO3 chlorobenzoic acid degrading bacteria of completely mineralizing the chlorinated benzoic acids produced during the Aroclor 1221 degradation. The depletion of these intermediates seems to prevent toxic or inhibitory effects on the bacteria thus permitting a larger Aroclor 1221 metabolization.

Abstract The effect of co-digesting sludge with bio-waste was investigated using an experimental apparatus set for reproducing the operating conditions of a full-scale digester in an existing wastewater treatment plant of 90,000 PE (population equivalent). An increase in the organic loading rate from 1.46 kgVS/m3 day to 2.1 kgVS/m3 day obtained by introducing 40 kg of biowaste per m3 of sludge in the digester caused an increase in the specific methane generation from 90 NL/kgVS to 435 NL/kgVS. These results were used to assess the energetic potential of digesters in eight existing wastewater treatment plants operating in an Italian province with 28,000 PE to 90,000 PE. Results showed that these facilities were able to co-digest globally about 2900 tonnes per year of bio-waste and to generate about 3400 MWh/year of electricity.