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In the present work, an anaerobic bioremediation treatment was investigated for reclamation of polycyclic aromatic hydrocarbons (PAHs) contaminated soil. The PAHs contaminated soil was artificially prepared and seven different contamination conditions were tested. In particular, four soils were contaminated solely by naphthalene (A), anthracene (B), pyrene (C) and benzo[a]pyrene (D), respectively, whereas, three soils were contaminated by benzo[a]pyrene coupled with one of the other investigated PAHs (i.e. A+D, B+D, and C+D tests). Such conditions were tested in order to study the possible degradation kinetic for the single involved PAH (with aromatic rings ranging from 2 to 5) as well as for PAHs mixed with a 5-aromatic rings contaminant (i.e. benzo[a]pyrene). The investigated treatment was carried out in bioaugmented condition through two microbial inocula obtained from anaerobic digestion tests on lignocellulosic substrate. In more detail, the two inocula were differently enriched through experiments characterized by sequential re-inoculation on new substrate, for its subsequent treatment, every 24 h and 96 h, respectively. The present study focused on the PAHs degradation efficiency and pathways, and microbiological abundance characterization, thus providing a comprehensive and interdisciplinary view to assess the feasibility of the suggested treatment in the field of PAHs contaminated soil remediation.

This study was carried out to evaluate the forage quantity and quality of several halophyte species grown in arid-saline environments. After identifying 44 halophytic species in the region and considering the potential of quantitative and qualitative forage production, 13 species from four families, i.e. Amaranthaceae, Asteraceae, Leguminosae and Convolvulaceae, and eight genera were selected for further evaluation. These species differed significantly in terms of both forage quantity, measured in terms of fresh (FW) and dry weight (DW), and forage quality assessed in terms of tissue water content (TWC), ash, nitrogen content (N), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), dry matter digestibility and metabolizable energy (ME). The highest fresh and dry weights were obtained from Suaeda ferticosa (1006.3 g and 306.3 g, respectively) and Noaea mucronata (909.3 g and 309 g, respectively). However, based on forage quality characteristics, Alhagi maurorum, Bassia scoparia, Noaea mucronata, Halostachys belangriana and Cressa cretica showed the best forage potential. Values of ash, CP, ADF, NDF and ME measured in the halophytes species ranged between 7.9% and 33.2%, 6.2% and 15.8%, 30.0% and 50.3%, 33.2% and 56.4%, 5.6 and 8.7 MJ kg−1, respectively. The forage quality of the evaluated halophytic plants was influenced by unfavorable environmental conditions such as high soil salinity and low rainfall, however, these species can be considered as new sources of forage. Nevertheless, further studies are needed to improve the quality of such halophytic species by reducing the ash content and increasing the ME.

A large amount of orange peel waste (OPW) is yearly generated due to the high production of oranges all over the world. A high percentage of this waste is dumped every year without any proper treatment, thus causing environmental issues as a consequence of dispersion of biological degradation by-products (i.e. biogas and leachate) into the environment. An effective, suitable and environmentally friendly treatment for OPW is therefore required. Biogas production under controlled conditions by an anaerobic digestion (AD) process is highly recommendable and it has been demonstrated to be potentially high efficient when OPW is used as substrate. However, the high content of essential oils, mainly composed of limonene, a well-known antioxidant, can cause the inhibition of the biological activity. A low limonene concentration inside the anaerobic digester can be effective to avoid this inhibition. Therefore, anaerobic co-digestion of OPW with organic fraction of municipal solid waste (OFMSW) was carried out in order to reduce limonene concentration, by dilution, in the organic mixture. Three different mass ratios of the two substrates (i.e. 1:3, 2:2, 3:1) were considered (each of them with different limonene concentrations) and used in two separate experiments: batch and semi continuous. The content of limonene inside the digester is directly related to the organic loading rate (OLR). The maximum OLR that resulted in stable anaerobic co-digestion process performance was 2 gVS(L−1·day−1) corresponding to 26.7 mgLimonene(Ldigester−1·day−1) of limonene dosage. The highest methane production obtained from such an OLR was around 0.70 ± 0.05 LCH4(Ldigester−1·day−1).

In the last decades, the worldwide interest in volatile fatty acids (VFAs) as basic elements for many industrial applications has been growing as fast as their market demand. Traditional production of VFAs from crude oil is unsustainable because of its environmental impact, therefore alternative solutions have been studied. The most promising solution has resulted in the VFAs production from organic waste based on biological processes thanks to the incoming environmental and economic benefits. In this scientific context, the state of current knowledge has not reached yet a satisfying level of comprehensiveness and it is mainly based on studies conducted at lab and pilot scale. Under the perspective to gain more knowledge and thus to promote an efficient as well as consolidated production of VFAs according to the key issues of the circular economy, a systematic and detailed study dealing with the impact of reactor configuration and relative operating conditions on biological VFAs production has been conducted. This step is a necessary condition to scale up the process and achieve its complete industrialization. According to this perspective and on the basis of the most recent findings from the international literature, the present review paper reports, as the main result of data elaboration, a novel one-to-one correspondence between organic wastes and reactor configurations having as target the VFAs yield enhancement.

Anaerobic digestion is a consolidated technology to convert sewage sludge and other organic wastes into biogas and a nutrient-rich fertilizer (i.e. digestate). The origin of sewage sludge does not exclude the potential presence of pathogens (e.g. Salmonella spp. and SARS-CoV-2) in mature digestate that hence could represent a source of sanitary concerns when it is spread on soil for agriculture purpose. Therefore, an experimental study aimed at proving the sanitizing effect of a full scale thermophilic high solids anaerobic digestion process was conducted by monitoring the hygienic characteristics of mature digestate. Although Salmonella spp. was detected and SARS-CoV-2 was presumably present in the sewage sludge fed to the full scale plant, the anaerobic digestion treatment demonstrated sanitization capacity since the monitored pathogens were never found in the mature digestate over the entire duration of the monitoring survey. Furthermore, tests on the regrowth of Salmonella Typhimurium and Escherichia coli, artificially inoculated on mature digestate, were also conducted under both anaerobic and aerobic conditions with the aim to assess the effectiveness of mature digestate as microbial growth medium. Concentrations of Salmonella Typhimurium and Escherichia coli were drastically reduced after a short time of incubation under anaerobic process and the two microorganisms already resulted undetectable after 24-48 h, whereas, under aerobic conditions, two microorganisms' concentrations were stably high for longer than 10 days. The combination of no free oxygen, high temperature, anaerobic metabolites (e.g. total ammonium nitrogen, and volatile fatty acids) production, bacteria competition and lack of nutritional elements in mature digestate considerably reduced in 24-48 h the sanitary risks associated to accidently contaminated digestate. Furthermore, a SARS-CoV-2 monitoring survey on mature digestate during 13 months, resulted in the absence of the virus RNA in the analyzed digestate.

Operations in copper sulfide flotation plants (CSFP) are complex and governed by several variables such as available technologies, reagents, and environmental conditions. However, few investigations are related to studying the microbial communities. These aspects provide a reason to compare the bacterial communities of two CSFP operated with freshwater (FwFlo) and seawater (SwFlo), and study whether indigenous bacteria could be used as pyrite bioreagents. Analyses were determined through next-generation sequencing by Illumina MiSeq System and conducted throughout the entire process: (i) minerals before and after grinding; (ii) final concentrate and concentrate thickener overflow; (iii) final tailings and tailings thickener overflow; and (iv) intake water. Bacterial strains from both plants were tested as potential bioreagents, given their tendency to adhere to pyrite after 5 min. In both CSFP, Proteobacteria (relative abundance from 45.48% to 79.22%), followed by Bacteroidetes (9.37%–44.7%), were the most abundant phyla. Regarding species, Algoriphagus olei (11.35%–43.52%) was present exclusively in FwFlo samples in contact with process water and absent in the mineral before grinding, where Cupriavidus metallidurans (16.05%) and Pseudomonas_uc (11.79%) predominated. In SwFlo samples, Marinobacter flavimaris (3.47%–41.1%), and GU061212-s (10.92%–27.63%), were the most abundant microorganisms. All of them were also detected in intake seawater. The strains with the highest adhesion rate (from 29.84% ± 0.14–100%) were phylogenetically identified as species of the genera Marinobacter, Pseudomonas, Idiomarina, Halomonas, Bacillus, Aerocuccus, and Peribacillus. Our results reveal that bacterial communities are critically dependent on process waters during mining activities, and our data depicted that indigenous bacteria could be used as potential pyrite bioreagents, evidenced by a high adhesion rate. It is thus possible to propose that different indigenous bacterial strains could be considered as new bioreagents to reduce the impact of conventional flotation reagents on health from an environment friendly perspective.

International audience; Cyanobacteria and microalgae are considered as interesting feedstocks for either the production of high value bio-based compounds and biofuels or wastewater treatment. Nevertheless, the high costs of production, mainly due to the harvesting process, hamper a wide commercialization of industrial cyanobacteria and microalgae based products. Recent studies have found in autoflocculation and bioflocculation promising spontaneous processes for a low-cost and environmentally sustainable cyanobacteria and microalgae biomass harvesting process. In the present work, bioflocculation process has been studied for three different inocula: filamentous cyanobacteria, microalgae and their mixture. Their cultivation has been conducted in batch mode using two different cultivation media: synthetic aqueous solution and urban wastewater. The removal of nutrients and flocculation process performance were monitored during the entire cultivation time. Results have proved that bioflocculation and sedimentation processes occur efficiently for filamentous cyanobacteria cultivated in synthetic aqueous solution, whereas such processes are less efficient in urban wastewater due to the specific characteristics of this medium that prevent bioflocculation to occur. Besides different efficiencies associated to cultivation media, this work highlighted that bioflocculation of sole microalgae is not as effective as when they are cultivated together with filamentous cyanobacteria.

Mining activities are among the main sources of potentially toxic elements (PTEs) in the environment which constitute a real concern worldwide, especially in developing countries. These activities have been carried out for more than a century in Chile, South America, where, as evidence of incorrect waste disposal practices, several abandoned mining waste deposits were left behind. This study aimed to understand multi-elements geochemistry, source patterns and mobility of PTEs in soils of the Taltal urban area (northern Chile). Topsoil samples (n = 125) were collected in the urban area of Taltal city (6km2) where physicochemical properties (redox potential, electric conductivity and pH) as well as chemical concentrations for 35 elements were determined by inductively coupled plasma optical emission spectrometer. Data were treated following a robust workflow, which included factor analysis (based on ilr-transformed data), a new robust compositional contamination index (RCCI), and fractal/multi-fractal interpolation in GIS environment. This approach allowed to generate significant elemental associations, identifying pool of elements related either to the geological background, pedogenic processes accompanying soil formation or to anthropogenic activities. In particular, the study eventually focused on a pool of 6 PTEs (As, Cd, Cr, Cu, Pb, and Zn), their spatial distribution in the Taltal city, and the potential sources and mechanisms controlling their concentrations. Results showed generally low baseline values of PTEs in most sites of the surveyed area. On a smaller number of sites, however, higher values concentrations of As, Cd, Cu, Zn and Pb were found. These corresponded to very high RCCI contamination level and were correlated to potential anthropogenic sources, such as the abandoned mining waste deposits in the north-eastern part of the Taltal city. This study highlighted new and significant insight on the contamination levels of Taltal city, and its links with anthropogenic activities. Further research is considered to be crucial to extend this assessment to the entire region. This would provide a comprehensive overview and vital information for the development of intervention limits and guide environmental legislation for these pollutants in Chilean soils.

Bioflocculation phenomena for filamentous cyanobacteria were studied and analysed in two different cultivation systems (i.e. based on air-bubbling and on shaking) and for different initial biomass concentrations. Floc formation and biomass settling were monitored during batch cultivation tests according to an innovative protocol. Results showed that the two cultivation systems enhanced two different flocculation behaviours: air bubbling led to the formation of small and dense flocs, while the shaking table resulted in larger (14 mm2 vs 4 mm2) but mechanically weaker flocs. Floc analysis evidenced that the different mixing systems also affected the speciation of biomass. A mathematical model was developed to simulate and predict the settling performance during the bioflocculation process of filamentous cyanobacteria. Natural settling was examined at different phases of biomass growth. Optimal conditions were obtained at the end of the exponential growth phase, when 70% of the total cultivated biomass could be recovered.

A pretreatment with H2O2 was conducted to improve the performance of the anaerobic digestion (AD) process for a partial treatment of tannery wastewater (TWW). Four different H2O2 dosages (0.5, 1, 2, and 4 g/L) were tested by adding to TWW different volumes of a 30% (m/v) H2O2 solution in order to improve the biodegradability of TWW organic load and decrease the total Cr concentration. Indeed, a less total Cr concentration was detected in pretreated samples that showed a minimum removal efficiency of 11% and a maximum removal efficiency of 41%. Moreover, several Biomethane Potential tests (BMP) were conducted to assess the enhanced biodegradability of pretreated TWW. Methane yields resulted in 594, 1151, 1090, 767, and 525 mL CH4/g TVS for the unpretrated TWW and for those pretreated with 0.5, 1, 2, and 4 g/L of H2O2, respectively. BMP tests proved that the best pretreatment condition for TWW, in terms of methane production and consequently total COD reduction, was achieved with a low dosage of H2O2 (0.5 g H2O2/L), corresponding to 1.0·10−4 g H2O2/g TVS and 3.2·10−5 g H2O2/g COD, whereas the highest dosage (4 g H2O2/L) was not related to the highest methane yield. Such contradictory results highlights the relevance of an appropriate dosage of H2O2, Finally, a kinetic study was also conducted.

This paper proposes an innovative bioaugmentation approach for the remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soils, based on a novel habitat-based strategy. This approach was tested using two inocula (i-24 and i-96) previously enriched through an anaerobic digestion process on wheat straw. It relies on the application of allochthonous microorganisms characterized by specific functional roles obtained by mimicking a natural hydrolytic environment such as the rumen. The inocula efficiency was tested in presence of naphthalene alone, benzo[a]pyrene alone, and a mix of both of them. In single-contamination tests, i-24 inoculum showed the highest biodegradation rates (84.7% for naphthalene and 51.7% for benzo[a]pyrene). These values were almost 1.2 times higher than those obtained for both contaminants with i-96 inoculum and in the control test in presence of naphthalene alone, while they were 3 times higher compared to the control test in presence of benzo[a]pyrene alone. In mixed-contamination tests, i-96 inoculum showed final biodegradation efficiencies for naphthalene and benzo[a]pyrene between 1.1 and 1.5 higher than i-24 inoculum or autochthonous biomass. Total microbial abundances increased in the bioaugmented tests in line with the PAH degradation. The microbial community structure showed the highest diversity at the end of the experiment in almost all cases. Values of the Firmicutes active fraction up to 7 times lower were observed in the i-24 bioaugmented tests compared to i-96 and control tests. This study highlights a successful bioaugmentation strategy with biological components that can be reused in multiple processes supporting an integrated and environmentally sustainable bioremediation system.

Extracellular polymeric substances (EPS) from different Anammox biomass were extracted and characterized by quantitative and qualitative analysis to investigate the link between their characteristics and the enrichment process in lab scale bioreactors. Quantitatively, a decrease of protein to polysaccharide ratio and an increase in total EPS extraction yield were observed during the enrichment process. In the three dimensional excitation emission matrixes, the spectra showed similar location of the fluorescence peaks for all of the samples. Whereas, samples extracted from sludge containing enriched Anammox bacteria possessed two distinct peaks in the low excitation wavelength range (220–230 nm). Multi-excitation peaks might occur as evidenced by the identical fluorescence chromatograms after size exclusion chromatography (SEC) separation at excitation/emission wavelength of 221/350 nm and 280/330 nm. With the process of Anammox enrichment, UV chromatogram at 210 nm after SEC, which is an indicator of polysaccharides, showed increase in both intensity and number of peaks. However, all fluorescence chromatograms, which reflect proteins and soluble microbial by-products, showed similar peak patterns with increased intensity. An increase of EPS hydrophobicity was observed during the enrichment process for both reactors.

Thermotoga neapolitana is a hyperthermophilic eubacterium that produces hydrogen by sugar fermentation. A lab strain of T. neapolitana DSMZ 4359(T) maintained in a CO2-enriched atmosphere showed a stable increase of lactic acid production under capnophilic lactic fermentation (CLF) conditions. The genotypic comparison between the putative mutant (TN-CMut) and the original strain DSMZ 4359(T) (WT4359) revealed 88.1 (+/- 2.4)% DNA homology. RiboPrint (R) and MALDI-TOF mass analyses support a genetic differentiation beyond subspecies level. The phenotypic characterization indicated a high correlation between the two strains, except for the lactic acid production. Under identical operating conditions, the lab mutant produced significantly more lactic acid than the parent strain without impairing the hydrogen yield. The highest divergence between TN-CMut and WT4359 was observed for fermentation of glucose or lactose at 80 degrees C. Based on these results, we propose that the lab strain is a new subspecies of the genus Thermotoga that is named T. neapolitana subsp. capnolactica with regards to its improved feature to produce lactic acid under capnophilic conditions. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

This study investigated the effect of the salinity level, buffering agent and carbon source on the hydrogen (H2) and lactic acid synthesis under capnophilic (CO2-assisted) lactic fermentation (CLF) by Thermotoga neapolitana cf capnolactica (DSM 33003). Several series of batch fermentation experiments were performed either in 0.12 L serum bottles for selection of the best performing conditions or in a 3 L fermenter for the best possible combination of conditions. The serum bottle study revealed that change in the salinity level of the culture medium from 0 to 35 g L−1 NaCl increased lactic acid synthesis by 7.5 times without affecting the H2 yield. Use of different buffers (MOPS, TRIS or HEPES) did not affect the average H2 yield of 3.0 ± 0.24 mol H2 mol−1 of glucose and lactic acid synthesis of 13.7 ± 1.03mM when the cultures were sparged by CO2. Among the carbonsources investigated, glucose was found to be the best performing carbon source for the CLF fermentation with 35 g L−1 of NaCl and 0.01M of phosphate buffer. Hence, an up-scale experiment using a 3 L fermenter and the combination of the best performing conditions showed a 2.2 times more lactic acid synthesis compared to the 0.12 L serum bottle experiments. The study reveals the robustness and flexibility of the CLF-based technology using T. neapolitana cf capnolactica fermentation under various operating environmental conditions.

Orange peel waste is considered as an important feedstock for anaerobic digestion to generate bio-energy such as bio-hydrogen and bio-methane; however, its use as an energy source is still not important worldwide. Therefore, in the current study, the biochemical methane potential test was carried out to estimate the biogas production from orange peel waste by using an anaerobic digestion process in the thermophilic phase (T = 55°C). In order to investigate the antimicrobial and the inhibiting effect of limonene contained in orange peels on biogas production two experimental setups were operated simultaneously using de-oiled and crude orange peel wastes, respectively. For further enhancement of the biogas production, a pre-treatment was applied using hydrogen peroxide (H2O2) at different concentrations up to the optimum value to increase soluble chemical oxygen demand (COD). The obtained results showed an important increase in biogas production: From 170 mL.gTVS−1 for the untreated sample to 750 mL.gTVS−1 after pre-treatment, and the composition analysis of the biogas indicated that average methane yields represent up to 50% of the total production. This increase was observed after steam distillation and was attributed to the removal of the antimicrobial compound.

Prezioso esemplare dell'Eneide, con frontespizio decorato e due bellissime tavole che rappresentano rispettivamente Annibal Caro fregiato con la corona d'alloro che traduce l'Eneide, e l'Argomento del poema così riassunto «Manda Eolo i venti à preghi di Giunone, E le navi Troiane à i lidi spinge De la nova Cartago: ivi riceve Enea la bella Dido; à cui Cupido sotto forma d'Ascanio ispira amore». L'Eneide, scritta da Publio Virgilio Marone tra il 29 a.C. e il 19 a.C., narra la leggendaria storia dell'eroe troiano Enea, figlio di Anchise e di Venere, che riuscì a fuggire dopo la caduta della città di Troia, e che viaggiò per il Mediterraneo fino ad approdare nel Lazio, diventando il progenitore del popolo romano. L'Eneide è una delle fonti cui guarda Vico nella Scienza nuova per ricostruire la storia di Roma antica, e l'eredità di Virgilio è presente pure nel forte legame tra ingenium e natura che caratterizza gli esseri viventi.

This study investigates the importance of the organic matter characteristics of several organic amendments (i.e., buffalo manure, food and kitchen waste, fruit and vegetables waste, and activated sewage sludge) and their influence in the bioremediation of a polycyclic aromatic hydrocarbons (PAH)-contaminated soil. The removal of low molecular weights (LMW) and high molecular weights (HMW) PAHs was monitored in four bioremediation reactors and used as an indicator of the role of organic amendments in contaminant removal. The total initial concentration of LMW PAHs was 234mgkg−1 soil (dry weight), while the amount for HMW PAHs was 422mgkg−1 soil (dry weight). Monitoring of operational parameters and chemical analysis was performed during 20weeks. The concentrations of LMW PAH residues in soil were significantly lower in reactors that displayed a mesophilic phase, i.e., 11 and 15%, compared to reactors that displayed a thermophilic phase, i.e., 29 and 31%. Residual HMW PAHs were up to five times higher compared to residual LMW PAHs, depending on the reactor. This demonstrated that the amount of added organic matter and macronutrients such as nitrogen and phosphorus, the biochemical organic compound classes (mostly soluble fraction and proteins), and the operational temperature are important factors affecting the overall efficiency of bioremediation. On that basis, this study shows that characterization of biochemical families could contribute to a better understanding of the effects of organic amendments and clarify their different efficiency during a bioremediation process of PAH-contaminated soil.

Food waste (FW) represents a source of high potential renewable energy if properly treated with anaerobic digestion (AD). Pretreating the substrates could yield a higher biomethane production in a shorter time. In this study, the effects of thermal (heating the FW in a separate chamber) and thermophilic (heating the full reactor content containing both FW and inoculum) pretreatments at 50, 60, 70 and 80. °C prior to mesophilic AD were studied through a series of batch experiments. Pretreatments at a lower temperature (50. °C) and a shorter time (55. °C) and longer operating times (>12. h) yielded higher soluble chemical oxygen demand (CODs), but had a negative effect on the methanogenic activity. The thermal pretreatments at the same conditions resulted in a lower solubilization of COD. Based on net energy calculations, the enhanced biomethane production is sufficient to heat up the FW for the thermal, but not for the thermophilic pretreatment.

The use of bacterial strains as agents in bioremediation processes could reduce the harmfulness of potential toxic elements (PTEs) from water and soil with low or even no impact on the natural ecosystems. In this study, two new metal resistant-bacterial strains (Q3 and Q5) of Bacillus sp. were isolated from a sulfurous spring and their potential (as pure cultures or mixed) to remove Pb(II) and Cd(II) from an aqueous matrix was evaluated and optimized using response surface methodology (RSM). The optimal conditions for Cd(II) removal from all tested strains combinations were observed at an initial pH 5, a temperature of 38 &deg, C, and an initial Cd(II) concentration of 50 mg L&minus, 1, while the performance of bacterial strains on Pb(II) removal was strongly correlated to initial pH and temperature conditions. Moreover, the efficiency of bacterial strains in removing both PTEs, Pb(II) and Cd(II), from an aqueous matrix was considerably higher when they were used as a mixed culture rather than pure. According to field emission SEM (FESEM) and EDS analysis, the two bacterial strains showed different mechanisms in removing Cd(II): Bacillus sp. Q5 bio-accumulated Cd(II) in its periplasmic space, whereas Bacillus sp. Q3 bio-accumulated Cd(II) on its cell surface. On the other hand, Pb(II) is removed by chemical precipitation (lead sulfide) induced by both Bacillus sp. Q3 and Q5. This study discloses new aspects of Pb(II) and Cd(II) bioremediation mechanisms in Bacillus species that can be extremely useful for designing and operating novel PTEs bioremediation processes.

The objective of this study was to enhance the hydrogen production rate of dark fermentation in batch operation. For the first time, the hyperthermophilic pure culture of Thermotoga neapolitana cf. Capnolactica was applied at elevated biomass concentrations. The increase of the initial biomass concentration from 0.46 to 1.74 g cell dry weight/L led to a general acceleration of the fermentation process, reducing the fermentation time of 5 g glucose/L down to 3 h with a lag phase of 0.4 h. The volumetric hydrogen production rate increased from 323 (+/- 11) to 654 (+/- 30) mL/L/h with a concomitant enhancement of the biomass growth and glucose consumption rate. The hydrogen yield of 2.45 (+/- 0.09) mol H-2/mol glucose, the hydrogen concentration of 68% in the produced gas and the composition of the end products in the digestate, i.e. 62.3 (+/- 2.5)% acetic acid, 23.5 (+/- 2.9)% lactic acid and 2.3 (+/- 0.1)% alanine, remained unaffected at increasing biomass concentrations. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Thermotoga neapolitana is capable to produce bio-hydrogen at high yields in hyperthermophilic dark fermentation from a large variety of substrates including organic wastes. However, in dark fermentation hydrogen concentration is one of the main inhibitors affecting the hydrogen yield and production rate. In this study, the effect of agitation speed and recirculation of the produced biogas on dissolved hydrogen concentration and its impact on hydrogen production by Thermotoga neapolitana were investigated. In 2 L batch bioassays using 1% inoculum (v/v), an increase of the agitation speed from 300 to 500 rpm led to a decrease of the dissolved hydrogen concentration from 17.0 ± 2.3 to 7.4 ± 0.7 mL/L. As a result, the hydrogen production rate and the glucose consumption rate increased from 54 ± 13 to 112 ± 22 mL H2/L/h and from 3.6 ± 0.4 to 4.7 ± 0.3 mmol glucose/L/h, respectively. In a second stage, the biomass concentration was increased to 0.8 g initial cell dry weight /L (equal to 200% inoculum v/v), applying agitation exclusively (low agitation “LA” - 300 rpm; high agitation “HA” - 500 rpm) and agitation combined with gas recirculation “GaR” (“LA+GaR” - 300 rpm; “HA+GaR” - 500 rpm). Gas recirculation increased the hydrogen production rate (ml H2/L/h) from 235 ± 35 (LA) and 535 ± 35 (HA) to 850 ± 71 (LA+GaR) and 813 ± 18 (HA+GaR). Concomitantly, the hydrogen yield (mol H2/ mol glucose) was increased from 3.0 ± 0.0 (LA) and 3.2 ± 0.1 (HA) to 3.5 ± 0.2 (LA+GaR) and 3.3 ± 0.1 (HA+GaR), respectively. At the same time, the fermentation time was reduced from 11 (LA) and 6 h (HA) to 4 h (LA+GaR; HA+GaR). The previous results confirm that the dissolved hydrogen plays a crucial role in dark fermentation hydrogen production even under hyperthermophilic stirred conditions. At higher biomass concentrations, the increase of the agitation speed increased the hydrogen yield and production rate by approximately 9 and 128% (HA/LA). In comparison, the application of the biogas recirculation increased the hydrogen yield and production rate by approximately 17 and 262% (LA+GaR/LA). The increase of agitation speed had a little effect when gas recirculation was applied, as indicated by the similar results achieved under LA+GaR and HA+GaR conditions. The present study confirms that gas recirculation is a simple and effective method to eliminate hydrogen supersaturation, considerably accelerating the hydrogen production and enhancing the yield.

Treatment of food waste by anaerobic digestion can lead to an energy production coupled to a reduction of the volume and greenhouse gas emissions from this waste type. According to EU Regulation EC1774/2002, food waste should be pasteurized/sterilized before or after anaerobic digestion. With respect to this regulation and also considering the slow kinetics of the anaerobic digestion process, thermal and chemical pretreatments of food waste prior to mesophilic anaerobic digestion were studied. A series of batch experiments to determine the biomethane potential of untreated as well as pretreated food waste was carried out. All tested conditions of both thermal and ozonation pretreatments resulted in an enhanced biomethane production. The kinetics of the anaerobic digestion process were, however, accelerated by thermal pretreatment at lower temperatures (

Microalgae cultivation systems fed with wastewater as source of nutrients represents the principal sustainable condition to produce microalgal biomass to be converted conveniently to biofuels. In order to optimize microalgae growth and their lipid content, the effect of light intensity and nutrients load in real wastewater was investigated through batch microalgal cultivation tests. A microalgal polyculture was used as inoculum and grown for 10 days in batch at different conditions of light intensity (i.e. 20, 50 and 100 μmol s−1m−2) and nutrients concentration in wastewater. Experimental results showed that biomass productivity decreased for rich nutrients conditions and increased for high light intensities. The highest lipid mass content (29%) was found for high light intensity condition (100 μmol s−1m−2). Furthermore, microalgae settleability tests, conducted at the end of the cultivation time, resulted in the highest biomass recovery efficiency (72%) for low light intensity and nutrients supply conditions.

Dairy wastes can be conveniently processed and valorized in a biorefinery value chain since they are abundant, zero-cost and all year round available. For a comprehensive knowledge of the microbial species involved in producing biofuels and valuable intermediates from dairy wastes, the changes in bacterial and archaeal population were evaluated when H2, CH4 and chemical intermediates were produced. Batch anaerobic tests were conducted with a mixture of mozzarella cheese whey and buttermilk as organic substrate, inoculated with 1% and 3% w/v industrial animal manure pellets. The archaeal methanogens concentration increased in the test inoculated at 3% (w/v) when H2 and CH4 production occurred, being 1 log higher than that achieved in the test inoculated at 1% (w/v). Many archaeal species, mostly involved in the production of CH4, were identified by sequencing denaturing gradient gel electrophoresis (DGGE) bands. Methanoculleus, Methanocorpusculum and Methanobrevibacter genera were dominant archaea involved in the anaerobic process for bioenergy production from mozzarella cheese whey and buttermilk mixture.

Solid-liquid extraction (adsorption or ion exchange) is a promising approach for the in situ separation of organic acids from fermentation broths. In this study, a diluted concentration of lactic acid (< 10 g/L) separation from a model fermentation broth by granular activated carbon (GAC) as well as weak (Reillex (R) 425 or RLX425) and strong (Amberlite (R) IRA-400 or AMB400) base anion exchange resins under various operating conditions was experimentally investigated. Thermodynamic analysis showed that the best lactic acid adsorption performances were obtained at a pH below the pKa value of lactic acid (i. e., 3.86) for GAC and RLX425 by physical adsorption mechanism and above the pKa value for the AMB400 resin by an ion exchange mechanism, respectively. The adsorption capacity for GAC (38.2 mg/g) was the highest, followed by AMB400 (31.2 mg/g) and RLX425 (17.2 mg/g). As per the thermodynamic analysis, the lactic acid adsorbed onto GAC and RLX425 through a physical adsorption mechanism, whereas the lactic acid adsorbed onto AMB400 with an ion exchange mechanism. The Langmuir adsorption isotherm model (R-2 > 0.96) and the pseudo-second order kinetic model (R-2 similar to 1) fitted better to the experimental data than the other models tested. Postulating the conditions for the real fermentation broth (pH: 5.0-6.5 and temperature: 30-80 degrees C), the resin AMB400 represents an ideal candidate for the extraction of lactic acid during fermentation.

The removal of polycyclic aromatic hydrocarbons (PAHs) from a naturally co-contaminated soil by PAHs and heavy metals with an initial concentration of 620 mg of total PAHs kg(-1) dry soil was investigated. The efficiency of landfarming in removing phenanthrene, pyrene, benzo(a)pyrene and the group of total 16 US EPA PAHs was evaluated. The process was biostimulated by adding centrifuged activated sewage sludge (SS) as an organic amendment. The tested ratios of contaminated soil to SS were 1:2, 1:1, 1:0.5 and 1:0 as wet weight basis. The process performance was monitored through chemical, microbiological and ecotoxicological analyses during 105 days of incubation. The results of analyses demonstrated that the treatment without centrifuged SS achieved a significantly higher total 16 US EPA PAH removal efficiency (i.e. 32%) compared to treatments with amendment. In the same treatment, the removal efficiency of the PAH bioavailable fraction was 100% for phenanthrene, benzo(a)pyrene and the group of total 16 US EPA PAHs, whereas 76% for pyrene. Ecotoxicity test performed with bioluminescent bacteria Vibrio fischeri confirmed the effectiveness of landfarming. Finally, the results showed that indigenous microorganisms under certain and controlled operating conditions have greater potential for PAH biodegradation compared to allochthonous microorganisms.

The current study aims to tackle one of the main obstacles in the application of anaerobic ammonium oxidation (Anammox) technology, i.e., the extreme slow growth of the Anammox bacteria. Three conventional sludge has been tested in sequencing batch reactor for Anammox enrichment, including conventional aerobic sludge, denitrification sludge, and anaerobic sludge. With a high selection stress and insufficient oxygen control, the reactor seeded with aerobic sludge reached 50–60% total nitrogen removal after 240days whereas that seeded with anaerobic sludge failed to establish Anammox activity. Anammox process was successfully established in the reactor seeded with denitrification sludge with a total nitrogen removal of approximately 80% after 150days under strict oxygen control (DO

Wastewater treatment plants (WWTPs) contribute to CO 2 emissions in atmosphere through direct (biological metabolism) and indirect (fuel combustion) oxidation of organic carbon. This detrimental effect of WWTPs operation can be mitigated by integrating the traditional treatment with a microalgae cultivation pond where CO 2 is fixed into autotrophic biomass and the positive side effect of removing nutrients also takes place. To test the feasibility of this modified WWTPs configuration, a pilot-scale 200 L raceway pond, operating outdoor, was designed and used for biomass cultivation in untreated urban wastewater. Nitrogen gas enriched with 20% CO 2 , simulating the exhausted gas of biogas combustion, was supplied continuously during daytime at different flowrates. The dynamics of microalgae growth as well as inorganic carbon and nutrients uptake were studied during the pond start-up and semi-continuous feeding conditions. The absorbed bio-available CO 2 was monitored during daylight for different gas flowrates (0.2, 0.4 and 1.0 L/min) and for wastewater semi-continuous feeding conditions (0.8 L/h). The highest efficiency, equal to 83%, of bio-available CO 2 fixation was obtained for the lowest gas flowrate of 0.2 L/min., whereas the highest CO 2 removal rate of 24.6 mg/L/min was reached for the highest gas flowrate of 1.0 L/min. Furthermore, this operating condition resulted in the highest microalgae biomass productivity of 28.3 g/d/m 2 . Nutrients removal was complete for each operating condition tested.

Landfarming is an attractive bioremediation treatment approach for soils contaminated with polycyclic aromatic hydrocarbons (PAHs), since it is less expensive and more environmentally friendly than other soil remediation methods. PAHs are contaminants of concern due to their potentially harmful effects on human health. Therefore interest in developing removal methods has grown in the last few decades. These persistent and hydrophobic organic pollutants are commonly found at high concentrations in soils contaminated by industrial activities and nearby urban areas, and these hazardous situations make their removal even more urgent. This paper reviews the efficiency and application conditions of landfarming as a suitable bioremediation treatment. Moreover, this work discusses the feasibility of improving the bioremediation performance when landfarming is combined with biostimulation and bioaugmentation promoted by the composting of organic waste. This integration of landfarming and composting creates more favorable conditions for biological activity and has been shown to be both effective and economical in removing organic pollutants from contaminated soils.

Recently, issues concerning the sustainable and harmless disposal of organic solid waste have generated interest in microbial biotechnologies aimed at converting waste materials into bioenergy and biomaterials, thus contributing to a reduction in economic dependence on fossil fuels. To valorize biomass, waste materials derived from agriculture, food processing factories, and municipal organic waste can be used to produce biopolymers, such as biohydrogen and biogas, through different microbial processes. In fact, different bacterial strains can synthesize biopolymers to convert waste materials into valuable intracellular (e.g., polyhydroxyalkanoates) and extracellular (e.g., exopolysaccharides) bioproducts, which are useful for biochemical production. In particular, large numbers of bacteria, including Alcaligenes eutrophus, Alcaligenes latus, Azotobacter vinelandii, Azotobacter chroococcum, Azotobacter beijerincki, methylotrophs, Pseudomonas spp., Bacillus spp., Rhizobium spp., Nocardia spp., and recombinant Escherichia coli, have been successfully used to produce polyhydroxyalkanoates on an industrial scale from different types of organic by-products. Therefore, the development of high-performance microbial strains and the use of by-products and waste as substrates could reasonably make the production costs of biodegradable polymers comparable to those required by petrochemical-derived plastics and promote their use. Many studies have reported use of the same organic substrates as alternative energy sources to produce biogas and biohydrogen through anaerobic digestion as well as dark and photofermentation processes under anaerobic conditions. Therefore, concurrently obtaining bioenergy and biopolymers at a reasonable cost through an integrated system is becoming feasible using by-products and waste as organic carbon sources. An overview of the suitable substrates and microbial strains used in low-cost polyhydroxyalkanoates for biohydrogen and biogas production is given. The possibility of creating a unique integrated system is discussed because it represents a new approach for simultaneously producing energy and biopolymers for the plastic industry using by-products and waste as organic carbon sources.

Wastewater disposal systems are complex systems composed by several interconnected elements. In the aftermath of dramatic natural events, such as the earthquake, the failure of any of these elements can result in the deterioration of the environment as well as in the risk for the exposed population, due to leakage of untreated or un-properly treated wastewater on soil and/or its discharge into superficial waters. This paper presents a multi-disciplinary methodology for the evaluation of the seismic vulnerability of municipal or industrial wastewater treatment plants, based on damage observation of available earthquake reports. Specific fragility curves and threshold values expressed in terms of Peak Ground Acceleration (PGA) are presented and compared with existing functions. The methodology fully comply requirements of most relevant and effective risk analysis tools or for land-use planning and can be adopted for the definition of structural priorities of plants.

The removal of polycyclic aromatic hydrocarbons (PAHs) from a spiked OECD (Organisation for Economic Co-operation and Development) artificial soil was investigated. Laboratory-scale thermally insulated bioremediation reactors were used to implement biostimulation strategy of composting. The selected PAHs included anthracene, chrysene, benzo(k)fluoranthene, and benzo(a)pyrene with an initial concentration of 658 mg of USEPA 16 PAHs kg−1 soil (d/w). The contaminants’ removal was improved by amending the contaminated soil with four different types of fresh organic waste. After 140 days of incubation, the removal of three-ring and four-ring PAHs in all reactors was higher than five-ring PAHs. The reactor displaying a mesophilic phase during bioremediation ended with a removal of 89 and 59 % for three-ring and four-ring PAHs, respectively. In contrast the reactor displaying a thermophilic phase ended with 71 and 41 % removal for three-ring and four-ring PAHs, respectively. The highest five-ring PAH removal was obtained for reactors with buffalo manure and sewage sludge amendments (40 and 33 %, respectively), while food and kitchen waste and fruit and vegetable waste amendments showed less efficiency (26 and 8 %, respectively). Microtox® test data indicated lower toxicity in reactor amended with sewage sludge considering that this setup reached the highest PAH removal and DHA (dehydrogenase activity) compared to others.